United Nations Scientific Committee on the Effects of Atomic Radiation

S O U R C E S , E F F E C T S A N D R I S K S O F I O N I Z I N G R A D I AT I O N

UNSCEAR 2020/2021 Report

Volume I
REPORT TO THE GENERAL ASSEMBLYSCIENTIFIC ANNEX A:
Evaluation of medical exposure to ionizing radiation

SOURCES, EFFECTS AND RISKSOF IONIZING RADIATION
United Nations Scientific Committee on the
Effects of Atomic Radiation
UNSCEAR 2020/2021
Report to the General Assembly,
with Scientific Annexes

VOLUME I
Scientific Annex A

UNITED NATIONSNew York, 2022

NOTE
The report of the Committee without its annexes appears as Official Records of the General
Assembly, Seventy-sixth Session, Supplement No. 46 (A/76/46).
The designations employed and the presentation of material in this publication do not imply theexpression of any opinion whatsoever on the part of the Secretariat of the United Nations concerning the legal status of any country, territory, city or area, or of its authorities, or concerning
the delimitation of its frontiers or boundaries.
The country names used in this document are, in most cases, those that were in use at the time thedata were collected or the text prepared. In other cases, however, the names have been updated,
where this was possible and appropriate, to reflect political changes.
The attachments cited in this annex are electronically available for download fromhttp://www.unscear.org/unscear/en/publications/2020_2021_1_Attachments.html

UNITED NATIONS PUBLICATION
Sales No. E.22.IX.1
ISBN: 978-92-1-139206-7
eISBN: 978-92-1-001003-0© United Nations, May 2022. All rights reserved, worldwide.
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CONTENTS
Page

VOLUME I
Report of the United Nations Scientific Committee on the Effects of Atomic Radiation
to the General Assembly .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .

1

Scientific Annexes
Annex A.	 Evaluation of medical exposure to ionizing radiation. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .

VOLUME II
Annex B.	 Levels and effects of radiation exposure due to the accident at the Fukushima Daiichi Nuclear Power
Station: Implications of information published since the UNSCEAR 2013 Report

VOLUME III
Annex C.	 Biological mechanisms relevant for the inference of cancer risks from low-dose andlow-dose-rate radiation

VOLUME IV
Annex D.	 Evaluation of occupational exposure to ionizing radiation

iii

39

Report of the United Nations Scientific Committee
on the Effects of Atomic Radiation

Contents
Chapter

Page

Part one. Report of the United Nations Scientific Committee on the Effects of Atomic Radiation on
its sixty-seventh session, held online from 2 to 6 November 2020 . . . . . . . . . . . . . . . . . . . .

1

I.

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1

II.

Deliberations of the United Nations Scientific Committee on the Effects of Atomic
Radiation at its sixty-seventh session . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2A.

Completed evaluations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3

B.

Present programme of work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4

1.

Occupational exposure to ionizing radiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4

2.

Public exposure to ionizing radiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

53.

Second primary cancer after radiotherapy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5

4.

Epidemiological studies of radiation and cancer . . . . . . . . . . . . . . . . . . . . . . . . . .

5

5.

Public information and outreach strategy (2020–2024) . . . . . . . . . . . . . . . . . . . .

6C.

Update on the implementation of the Committee’s long-term strategic directions . . .

6

D.

Future programme of work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8E.

Administrative issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9Scientific reports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

10A.

Evaluation of medical exposure to ionizing radiation . . . . . . . . . . . . . . . . . . . . . . . . . .

10

B.

Levels and effects of radiation exposure due to the accident at the Fukushima
Daiichi nuclear power station: implications of information published since the
UNSCEAR 2013 report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

13

1.

The accident and the releases of radioactive material into the environment . . . .

13

2.

Levels in the environment and food . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

13

3.

Dose assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

14

4.

Health implications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

16

5.

Radiation exposures and effects on non-human biota . . . . . . . . . . . . . . . . . . . . . .

17

Biological mechanisms relevant for the inference of cancer risks from low -dose andlow-dose-rate radiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

17Part two. Report of the United Nations Scientific Committee on the Effects of Atomic Radiation on
its sixty-eighth session, held online from 21 to 25 June 2021 . . . . . . . . . . . . . . . . . . . . . . . .

20

III.

C.

IV.

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

20

V.

Deliberations of the United Nations Scientific Committee on the Effects of Atomic
Radiation at its sixty-eighth session . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

21A.

Completed evaluations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

21

B.

Present programme of work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

22

1.

Second primary cancer after radiotherapy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

22

2.

Epidemiological studies of radiation and cancer . . . . . . . . . . . . . . . . . . . . . . . . . .

22

3.

Public exposure to ionizing radiation from natural and other sources . . . . . . . . .

22

v

4.

Implementation of the Committee’s strategy to improve collection, analysis anddissemination of data on radiation exposure, including consideration of theCommittee’s ad hoc working group on sources and exposure . . . . . . . . . . . . . . .
Implementation of public information and outreach strategy for 2020–2024 . . .

22

C.

Update on the implementation of the Committee’s long-term strategic directions . . .

24

D.

Future programme of work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

25

E.

Administrative issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

27

Scientific report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

30

Evaluation of occupational exposure to ionizing radiation . . . . . . . . . . . . . . . . . . . . . . . . . .

30

Members of national delegations attending the sixty-fourth to sixty-eighth sessions of theUnited Nations Scientific Committee on the Effects of Atomic Radiation in the
preparation of its scientific reports for 2020 and 2021 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

35

Scientific staff and consultants cooperating with the United Nations Scientific Committee
on the Effects of Atomic Radiation in the preparation of its scientific reports for 2020
and 2021 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

37

5.

VI.

24

Appendices
I.

II.

vi

REPORT TO THE GENERAL ASSEMBLY 1

Part one
Report of the United Nations Scientific Committee on the
Effects of Atomic Radiation on its sixty-seventh session, held
online from 2 to 6 November 2020
Chapter I
Introduction
1.
Since the establishment of the United Nations Scientific Committee on the Effectsof Atomic Radiation (UNSCEAR) by the General Assembly in its resolution 913 (X) of
3 December 1955, the mandate of the Committee has been to undertake broad
assessments of the sources of ionizing radiation and its effects on human health and theenvironment. 1 In pursuit of its mandate, the Committee thoroughly reviews andevaluates global and regional exposures to radiation. The Committee also evaluates
evidence of radiation-induced health effects in exposed groups and advances in theunderstanding of the biological mechanisms by which radiation-induced effects onhuman health or on non-human biota can occur. Those assessments provide the scientificfoundation used, inter alia, by the relevant agencies of the United Nations system informulating international standards for the protection of the general public, workers andpatients against ionizing radiation; 2 those standards, in turn, are linked to important
legal and regulatory instruments.
2.
Exposure to ionizing radiation arises from naturally occurring sources (such asradiation from outer space and radon gas emanating from rocks in the Earth) and fromsources with an artificial origin (such as medical diagnostic and therapeutic
procedures; radioactive material resulting from nuclear weapons testing; energy
generation, including by means of nuclear power; unplanned events such as thenuclear power station accident at Chernobyl in April 1986 and that following the greateast-Japan earthquake and tsunami of March 2011; and workplaces where there may
be increased exposure to artificial or naturally occurring sources of radiation).

__________________The United Nations Scientific Committee on the Effects of Atomic Radiation was established by
the General Assembly at its tenth session, in 1955. The terms of reference of the Committee areset out in resolution 913 (X). The Scientific Committee was originally composed of the following
States Members of the United Nations: Argentina, Australia, Belgium, Brazil, Canada,
Czechoslovakia (later succeeded by Slovakia), Egypt, France, India, Japan, Mexico, Sweden,
Union of Soviet Socialist Republics (later succeeded by the Russian Federation), United
Kingdom of Great Britain and Northern Ireland and United States of America. The membershipof the Scientific Committee was subsequently enlarged by the Assembly in its resolution 3154 C(XXVIII) of 14 December 1973 to include the Federal Republic of Germany (later succeeded byGermany), Indonesia, Peru, Poland and the Sudan. By its resolution 41/62 B of 3 December
1986, the General Assembly increased the membership of the Committee to 21 members andinvited China to become a member. In its resolution 66/70, the General Assembly further
enlarged the membership of the Committee to 27 and invited Belarus, Finla nd, Pakistan, theRepublic of Korea, Spain and Ukraine to become members.
2
For example, the International Atomic Energy Agency (IAEA) safety standard entitled Radiation
Protection and Safety of Radiation Sources: International Basic Safety Standards – General
Safety Requirements Part 3, co-sponsored by the European Commission, the Food andAgriculture Organization of the United Nations (FAO), IAEA, the International Labour
Organization (ILO), the Nuclear Energy Agency of the Organization for Economic Cooperation
and Development (NEA/OECD), the Pan American Health Organization (PAHO), the United
Nations Environment Programme (UNEP) and the World Health Organization (WHO).
1

2 UNSCEAR 2020/2021 REPORT

Chapter II
Deliberations of the United Nations Scientific Committee on
the Effects of Atomic Radiation at its sixty-seventh session
3.
The Scientific Committee held its sixty-seventh session online from 2 to
6 November 2020. 3 The following served as officers of the Committee: Gillian Hirth(Australia), Chair; and Jing Chen (Canada), Anna Friedl (Germany) and Jin Kyung
Lee (Republic of Korea), Vice-Chairs; and Anssi Auvinen (Finland) was elected as
Rapporteur for the sixty-seventh session.
4.
The Scientific Committee took note of and discussed General Assembly
resolution 74/81 on the effects of atomic radiation, in which the Assembly, inter alia:(a) requested the United Nations Environment Programme (UNEP) to continue,
within existing resources, to service the Committee and to disseminate its findings toMember States, the scientific community and the public and to ensure that theadministrative measures in place are appropriate, including clear roles, so that thesecretariat is able to adequately and efficiently service the Committee in a predictable
and sustainable manner and effectively facilitate the use of the invaluable expertise
offered to the Committee by its members in order that the Committee may discharge
the responsibilities and mandate entrusted to it by the General Assembly;(b) welcomed the appointment of a new Secretary of the Commi ttee by UNEP and
urged UNEP to ensure that future recruitment processes are conducted in an efficient,effective, timely and transparent manner; (c) welcomed the establishment of the postof Deputy Secretary, which replaces the previous post of Scientific Officer, allows forthe deputization of the Deputy Secretary as Secretary as appropriate and assists in the
avoidance of disruptions in staffing; and (d) requested the Secretary -General tostrengthen support for the Committee within existing resources, par ticularly withregard to the increase in operational costs in the case of a further increase inmembership, and to report to the General Assembly at its seventy-fifth session on
those issues.
5.
In regard to points (c) and (d) above, the Scientific Committee’s normal operation had
been impacted by the coronavirus disease (COVID-19) pandemic. The Committee
welcomed the establishment of the position of Deputy Secretary. However, the
COVID-19 pandemic resulted in a delay in the appointment of an officer to theposition of Deputy Secretary of the Committee, as the United Nations had
implemented a recruitment freeze for all regular budget -funded United Nations
posts. In addition, the Committee was unable to hold its sixty-seventh session in
July 2020 as originally planned and postponed the session until 2–6 November 2020,
when it was held online. Since it would not be timely to report to the General
Assembly after the planned sixty-seventh session in November 2020, it was decided
to report on the Committee’s intersessional activities by means of a note by the
Chair of the Committee (A/75/46) and an oral report before the conclusion of theseventy-fifth session of the General Assembly.
6.
In regard to points (a), (b) and (c) above, the Scientific Committee heard astatement from the representative of UNEP, who acknowledged and thanked theCommittee for its continued work and progress during the COVID -19 pandemic. He
explained the budget difficulties leading to the freeze of all recruitments for posts
under the United Nations regular budget, which had halted the recruitment of a
Deputy Secretary for the Committee, and noted that UNEP was committed to__________________
3

The sixty-seventh session of the Scientific Committee was attended by 212 participants from27 States members of the Committee, observers for Algeria, Iran (Islamic Republic of), Norway
and the United Arab Emirates, in accordance with paragraph 23 of General Assembly
resolution 74/81, and observers for the Comprehensive Nuclear-Test-Ban Treaty Organization,
the European Union, the International Agency for Research on Cancer, IAEA, the International
Commission on Radiation Units and Measurements (ICRU), the International Commission on
Radiological Protection (ICRP), FAO, ILO, NEA/OECD, UNEP and WHO.

REPORT TO THE GENERAL ASSEMBLY 3

completing the appointment of a Deputy Secretary for UNSCEAR as soon as theregular budget freeze was resolved. He expressed appreciation for the contributions
to the UNSCEAR general trust fund that had been received from Australia, Belgium,
Germany, Japan and Spain. The Committee also heard a statement from therepresentative of Indonesia. Issues raised by the Committee are reported inchapter II, section E (“Administrative issues”).

A.

Completed evaluations
7.
The Scientific Committee discussed three scientific annexes to the present
report (see chapter III), agreed on their findings and requested that the three scientificannexes be published in the usual manner, subject to the modifications agreed upon,and final adoption be conducted using a silence procedure due to the COVID-19
pandemic, as that procedure had been adopted by the Committee for use at the
sixty-seventh session.
8.
At its sixtieth session, the Scientific Committee had endorsed the plan for thecollection and evaluation of data on medical exposure. Given that radiation exposures ofpatients worldwide are the main artificial source of human exposure to ionizing
radiation, that there has been a continuing upward trend in collective doses topopulations and that the pace of technological development in this field continues toaccelerate, the Committee’s regular evaluations of collective doses to populations andtrends continue to be an important priority.
9.
As at 30 September 2019, 58 countries had submitted data on medical exposures,and the Scientific Committee recognized the efforts of the expert group on medical
exposure in carefully and systematically reviewing the submitted data and working
with national contact persons to clarify any ambiguities. 4 The Committee discussed
and approved for publication the scientific annex on the evaluation of medical
exposure to ionizing radiation.
10. At its sixty-fifth session, the Scientific Committee considered the project plan
to produce an update to annex A of the UNSCEAR 2013 report. 5 The aim was toproduce a report summarizing all information that was available by the end of 2019,on levels and effects of radiation exposure due to the accident at the Fukushima
Daiichi nuclear power station, and the implications of the new information for the
UNSCEAR 2013 report. At its sixty-sixth session, the Committee endorsed having amore focused scope of the detailed analyses of doses to the public and concurred thatthe outreach material on issues of considerable media or public interest should be
dealt with separately, as part of the secretariat’s outreach plan. At its sixty-seventhsession, the Committee discussed and approved for publication the scientific annex
on the levels and effects of radiation exposure due to the acciden t at the Fukushima
Daiichi nuclear power station: implications of information published since the
UNSCEAR 2013 report.
11. At its sixty-third session, the Scientific Committee decided to compile an
up-to-date overview of the following: up-to-date knowledge of biologicalmechanisms by which radiation influences the development of disease, in particular
at low incremental doses and low dose rates; the implications for the dose -response
relationships for health effects at low doses; and thus the relevance for es timating
associated risks to health, as well as the relevance for the inference of cancer risks.
An expert group was established that submitted progress reports to the Committee forconsideration at its sixty-fourth, sixty-fifth and sixty-sixth sessions. At its
sixty-seventh session, the Committee discussed and approved for publication the__________________

To put this in perspective, 58 countries is a small number of the total of 193 States Members of
the United Nations.
5
Sources, Effects and Risks of Ionizing Radiation: United Nations Scientific Committee on the
Effects of Atomic Radiation 2013 Report to the General Assembly, vol. I (United Nations
publication, 2014), annex A.
44 UNSCEAR 2020/2021 REPORT

scientific annex on the biological mechanisms relevant for the inference of cancer
risks from low-dose and low-dose-rate radiation.

B.

Present programme of work
12. The Scientific Committee took note of the progress report by the secretariat on
the collection, analysis and dissemination of data on radiation exposures of the public,
patients and workers, obtained from reviews of the scientific literature and the datasubmissions by Member States. The Committee recognized the efforts of thesecretariat in: (a) conducting outreach about the global surveys, which has contributed
to an increased number of nominations of national contact persons; and (b) supporting
the production of a simplified questionnaire to assist in the preparation of datasubmissions, which has had a positive impact on the number of submissions on public,
medical and occupational exposures. As at 30 September 2020, 90 countries had
nominated national contact persons for public exposure; 87 countries in the field of
medical exposure; and 68 countries in the field of occupational exposure. Although
this is a significant increase in participation in recent years, more participation andcontributions by Member States would be useful to ensure that the data arerepresentative.
13. The Scientific Committee expressed its continued support for the creation of a
network of national contact persons, using the UNSCEAR online platform as a toolfor communication among them for exchanging experiences on the process of datacollection. It also encouraged States Members of the United Nations to provide dataon medical, occupational and public exposures and encouraged continued futurecooperation of the Committee’s secretariat with Member States and relevantinternational organizations, in particular in the new UNSCEAR Global Survey of
Public Exposure, planned to commence in December 2020.
14. The Scientific Committee also noted that future evaluations of medical
exposures should focus on motivating Member States not represented in the present
global assessment to submit essential information. Actions should target, in particular,countries with developing levels of health care and those with large populations
because those countries are potentially significant contributors to global medical
exposure practice. A regional approach that facilitates data collection for theassessment of population dose could form the basis for surveys in regions whosecountries have similar health and economic indicators, such as in Africa, Asia andLatin America; that regional approach could include training and support on datacollection and evaluation for national contact persons. Data collection could befocused on the types of examinations that contribute most to the overall populationdose, which could help to increase future participation in the UNSCEAR Global
Survey of Medical Exposure.

1.

Occupational exposure to ionizing radiation
15. The Scientific Committee’s evaluations of worldwide occupational exposure toionizing radiation provide information relevant for policy and decision -making
regarding the use and management of radiation. The resulting dose distributions andtrends give insight into the main sources and situations of exposure and provide
information about the main factors influencing exposures. The evaluations assist in
identifying emerging issues and may indicate situations that should be subjected tomore attention and scrutiny.
16. The Scientific Committee has conducted evaluations of worldwide occupational
exposure and trends on the basis of two sources: (a) data from the UNSCEAR Global
Survey of Occupational Radiation Exposure; and (b) reviews of analyses publishedin peer-reviewed literature. At its sixty-sixth session, the Committee agreed to extend
the deadline for data collection to 30 September 2019. This resulted in data being
submitted by an additional 18 countries between April 2019 and October 2020.

REPORT TO THE GENERAL ASSEMBLY 5

17. The Scientific Committee acknowledged the work of the expert group in conducting
its systematic review of the literature and that the work of the expert group had been
delayed by one year owing to both the insufficient data provided by Member States andthe extended quality checks and corrections of available data. The report on the evaluationof occupational exposure to ionizing radiation is envisaged to be prepared for approval
for publication at the Committee’s sixty-eighth session, in June 2021.
2.

Public exposure to ionizing radiation
18. The Scientific Committee recalled that at its sixty-fourth session, the proposal toevaluate public exposure to ionizing radiation had been discussed. The Committee
decided at that time to postpone project initiation until its evaluation of lung cancerfrom exposure to radon had been completed. At its sixty-sixth session, the Committee
decided to commence its evaluation of public exposure to ionizing radiation, including
quality criteria for sources and exposure.
19. The Scientific Committee noted the commencement of the evaluation in 2020 anddiscussed the progress report. It recognized the progress made and agreed the proposed
revised plan for completion in 2024. The Committee noted the increased importance andbroad interest in this new evaluation, which will review and analyse scientific information
since 2007. As of October 2020, 36 experts from 17 Member States and observers fromfour international organizations were working on the update of the methodologies to be
applied and the literature review.
20. The Scientific Committee encouraged all Member States to participate andrespond to the UNSCEAR Global Survey of Public Exposure that is planned tocommence at the end of 2020.

3.

Second primary cancer after radiotherapy
21. At its sixty-third session, the Scientific Committee considered the issue of
second primary cancer after radiotherapy and discussed preliminary plans to launch a
project based on a proposal by the delegation of France. After further discussions at
the sixty-fourth session, the Committee reached agreement at its sixty -fifth session
on a project plan to evaluate second primary cancer after radiotherapy, emphasizingthat while the project was a priority, the work could not be started until after theappointment of the new Secretary. At its sixty-sixth session, the Committee endorsed
the plan presented by the expert group for initiating the work in late 2019 andrequested that the expert group provide a progress report at its sixty -seventh session,
including a first selection of literature on second primary cancer after radiotherapy,
an updated timetable and an advanced table of contents.
22. At its sixty-seventh session, the Scientific Committee took note of the launch of
the evaluation in 2019 and of the progress made to date and agreed with the updated
timetable for completion. That progress report included a description of the literature
research process and an update of the table of contents to include risk projections
based on patient-specific organ doses, meta-analyses to provide site-specific pooledrisk estimates and an assessment of the quality of dosimetry reporting. The expert
group will provide a progress report at the next session.

4.

Epidemiological studies of radiation and cancer
23. At its sixty-third session, the Scientific Committee discussed a preliminary plan
to provide a comprehensive scientific review of epidemiological studies of radiationand cancer to update annex A of the UNSCEAR 2006 report. 6 The Committee agreed
at its sixty-fifth session to initiate the comprehensive scientific review after both theappointment of the new Secretary and the initiation of the project on second primarycancer after radiotherapy are finalized.

__________________
6

Effects of Ionizing Radiation: United Nations Scientific Committee on the Effects of Atomic Radiation
2006 Report to the General Assembly, vol. I (United Nations publication, 2008), annex A.

6 UNSCEAR 2020/2021 REPORT

24. At its sixty-sixth session, the Scientific Committee approved the projec t plan,
requesting that the final report also include a summary written in language that could
be understood by members of the public. The Committee noted that the expert groupwould commence work in the third quarter of 2019 and requested that the expert groupprovide a progress report at its sixty-seventh session, including a first selection ofliterature on epidemiological studies on radiation and cancer, an updated timetable
and an advanced table of contents.
25. At its sixty-seventh session, the Scientific Committee took note of the launch of
the project in 2019 and the progress report on the project. That report included a
description of the literature search process and a revised workplan in which a report
would be submitted for approval in 2024. The Com mittee confirmed that theevaluation should be limited to cancer and not consider other health effects.
5.

Public information and outreach strategy (2020–2024)
26. At its sixty-sixth session, the Scientific Committee endorsed the secretariat’s
proposal for a new strategy on outreach activities for the period 2020 –2024. The lattercomplements the secretariat’s planned outreach activities on the update of annex A of
the UNSCEAR 2013 report on the levels and effects of radiation exposure due to theaccident at the Fukushima Daiichi nuclear power station.
27. At its sixty-seventh session, the Scientific Committee took note of a progress
report of the secretariat on the implementation of outreach activities in the period
2020–2024. That report included a summary of: (a) ongoing and future activities forthe dissemination of the Committee’s findings to a broader audience; (b) thestrengthening of collaboration and development of framework agreements withinternational organizations; and (c) improvement of the UNSCEAR website(including its translation into all official languages of the United Nations). The
Committee acknowledged the postponement of outreach activities on the update of
the UNSCEAR 2013 report due to the COVID-19 situation and encouraged close
collaboration with international organizations to further promote the Committee’sfindings. It also took note of the plans of the secretariat related to the celebration of
the sixty-fifth anniversary of UNSCEAR in 2021 and noted that the dissemination of
the Committee’s findings 7 is increasingly dependent on the availability of
extrabudgetary funds.

C.

Update on the implementation of the Committee’s long-term
strategic directions
28. At its sixty-sixth session, the Scientific Committee approved its long-term
strategic directions and plan for the period 2020 –2024. That plan included thefollowing:(a) Establishing working groups focused on sources and exposure, and effects
and mechanisms;(b) Inviting, on an ad hoc basis, scientists from other State s Members of theUnited Nations to participate in the Committee’s evaluations ;(c) Increasing the Committee’s efforts to present its evaluations andsummaries thereof in a manner that attracts readers without compromising scientificrigour and integrity;__________________
7

For example, the translation of the UNEP booklet entitled Radiation: Effects and Sources andparticipation in international events such as the Internation al Conference on a Decade of Progress
After the Fukushima-Daiichi: Building on the Lessons Learned to Further Strengthen Nuclear
Safety, originally to be held on 22–25 February 2021 and now rescheduled for 8–12 November
2021.

REPORT TO THE GENERAL ASSEMBLY 7(d) While maintaining the lead in providing authoritative scientificevaluations to the General Assembly, liaising closely with other relevant international
bodies to avoid duplication of efforts.
(a)

Establishing working groups focused on the areas of sources and exposure, andeffects and mechanisms
29. At its sixty-sixth session, the Scientific Committee: (a) established the ad hocworking group on sources and exposure; and (b) prolonged the activities of the ad hocworking group on effects and mechanisms until the Committee’s sixty-seventhsession in 2020, in order to finalize the proposal for the future programme of work on
effects and mechanisms of radiation exposure for the period 2020 –2024.
30. Bearing in mind the high-quality, important work conducted by the ad hocworking group on effects and mechanisms in developing the Scientific Committee’s
future programme of work (2020–2024), the Committee, at its sixty-seventh session,
extended the mandate of the ad hoc working group on effects and mechan isms for one
year to support and monitor progress in the implementation of the programme of workand to evaluate new scientific developments relevant for the Committee at its
sixty-eighth session in 2021.
31. At its sixty-seventh session, the Scientific Committee also acknowledged thehigh-quality, important work by the ad hoc working group on sources and exposureand endorsed the proposal for an extension of the work of the ad hoc working groupon sources and exposure for one more year to continue support and guide theimplementation of the processes for collection, analysis and dissemination of data onradiation exposures of the public, patients and workers. Both working groups willcontinue to consist of scientists selected for their competence, commitment andobjectivity.
32. The Scientific Committee emphasized that, except for the administrative support
from the secretariat, the extension of the work of the ad hoc working groups would
incur no additional costs for the United Nations.

(b)

Inviting, on an ad hoc basis, scientists from other States Members of the United
Nations to participate in the Committee’s evaluations
33. The Scientific Committee noted that the secretariat and the Bureau had taken
steps to involve scientists from other States Members 8 of the United Nations in
supporting the secretariat in conducting ongoing evaluations. This is particularly
relevant for the ongoing evaluation of public exposure to ionizing radiation fromnatural and other sources.

(c)

Increasing the Committee’s efforts to present its evaluations and summaries
thereof in a manner that attracts readers without compromising scientific rigour
and integrity
34. The Scientific Committee referred to the outreach activities reported in
section B.5 above.

(d)

While maintaining the lead in providing authoritative scientific evaluations to theGeneral Assembly, liaising closely with other relevant international bodies toavoid duplication of efforts
35. The importance of the Scientific Committee’s findings in providing thescientific evidence upon which decisions are made by the international community
and the safety standards are developed was also demonstrated in the period since thesixty-fifth session. The Committee noted that in 2020, UNSCEAR was invited toparticipate as an observer of the International Atomic Energy Agency (IAEA)
Commission of Safety Standards and as a member of the Steering Committee of the__________________
8

Austria, Italy, Norway, Singapore and Switzerland.

8 UNSCEAR 2020/2021 REPORT

Global Nuclear Safety and Security Network of IAEA. UNSCEAR is also cooperatingwith a number of organizations, including IAEA, the International Commission on
Radiological Protection (ICRP) and the International Radiation Protection
Association (IRPA) in relation to the dissemination of the UNSCEAR 2020 report on
the Fukushima accident. In addition, the 2019 report of the Secre tary-General
highlighted the importance of the Committee’s work for the scientific evaluation ofradiation exposure and the health effects of the Chernobyl accident. 9
36. The Scientific Committee welcomed and supported the continued cooperationof the secretariat with the United Nations and other international organizations 10 witha view to promoting the Committee’s work and exploring synergies and joint activities
that would contribute to that work and support the collection and analysis of scientific
data.

D.

Future programme of work
37. At its sixty-fifth session, the Scientific Committee established the ad hocworking group on effects and mechanisms. Since the sixty-fifth session, the ad hocworking group has collected and analysed the experience of and lessons learned by
the Committee in recent years and developed a draft future programme of workfor the period 2020–2024, which was first discussed by the Committee at its
sixty-sixth session. The ad hoc working group on effects and mechanisms also
supported the Bureau and the secretariat in monitoring progress on the curr ent
projects and in evaluating new scientific developments that occurred between thesessions, for consideration by the Committee.
38. At its sixty-seventh session, the Committee reviewed the draft future programmeof work for the period 2020–2024 and agreed that priority should be given toevaluations already initiated or planned to be started in 2020. This includes anevaluation of diseases of the circulatory system from radiation exposure, which, due
to the delay of the sixty-seventh session caused by the COVID-19 pandemic, is now
planned to begin in 2021. In approving the new programme of work, the Committee
agreed, in order to achieve a more balanced workload for the Committee and its
secretariat, to follow a general principle of starting one evaluation per year. Therefore,
the Committee is planning to initiate the evaluation of radiation effects on the nervous
system in 2022 and the evaluation of eye lens opacities from radiation exposure in
2023. In 2024, however, to ensure thematic consistency, the evalua tion of radiation
effects on the immune system will start simultaneously with an overarchingevaluation of non-cancer effects, which will include the following topics: acuteradiation syndrome, respiratory disease, endocrine disease, transgenerational effe cts
and other relevant non-cancer effects.
39. The Scientific Committee emphasized that timely programme implementationin the period 2020–2024 depends on having sufficient available resources in thesecretariat. The Committee acknowledged the request of the E xecutive Director of
UNEP for support in the form of financial contributions to the general trust fund. 11
Therefore, the Committee welcomed the contributions of five States members of theCommittee and encouraged other Member States to make use of the poss ibility tostrengthen the secretariat’s capacity through regular voluntary contributions to thegeneral trust fund and/or in-kind contributions, for example, experts working as
non-reimbursable loans, junior professional officers or United Nations volunteers.

__________________

See A/74/461.
For example, UNEP, IAEA, the European Union, the International Civil Aviation Organization(ICAO), NEA/OECD, the Inter-Agency Committee on Radiation Safety (IACRS), theInternational Radiation Protection Association, ICRP and ICRU.
11
The programme for the United Nations Scientific Committee on the Effects of Atomic Radiation(UNSCEAR) general trust fund for the period 2019–2021 has been prepared, and a note verbale
in that regard has been sent to the Member States.
9

10

REPORT TO THE GENERAL ASSEMBLY 9

40. The Scientific Committee requested the two ad hoc working groups to develop
a proposal for the scope and contents of a guidance document detailing the principles
and criteria for ensuring the quality of the Committee’s use of radiation protection
quantities and units (including the use of collective effective doses), with a view toholding a discussion at the sixty-eighth session on how this guidance could be
published in the future.

E.

Administrative issues
41. The Scientific Committee took note of General Assembly resolution 74/81 on
the effects of atomic radiation, in which the Assembly:(a) Requested UNEP to continue, within existing resources, to service theCommittee and to disseminate its findings to Member States, the scientific community
and the public and to ensure that the administrative measures in place wereappropriate, including clear roles, so that the secretariat is able to adequately andefficiently service the Committee in a predictable and sustainable manner andeffectively facilitate the use of the invaluable expertise offered to the Committee by
its members in order that the Committee might discharge the resp onsibilities andmandate entrusted to it by the General Assembly;(b) Welcomed the appointment of a new Secretary of the Scientific Committee
by UNEP and urged UNEP to ensure that future recruitment processes were conductedin an efficient, effective, timely and transparent manner;(c) Welcomed the establishment of the post of Deputy Secretary, which
replaces the previous post of Scientific Officer, allows for the deputization of the
Deputy Secretary as Secretary as appropriate, and assists in the avoidance ofdisruptions in staffing;(d) Requested the Secretary-General to strengthen support for the Committee
within existing resources, particularly with regard to the increase of operational costsin the case of a further increase in membership, and to report to the General Assemblyat its seventy-fifth session on those issues.
42. In considering the requests of the General Assembly, the Scientific Committee
noted the statement by UNEP and strongly encouraged the finalization of the post of
Deputy Secretary as soon as possible. The Committee also noted that the budget of
the UNSCEAR secretariat was at its lowest level ever, and expressed concern about
the Committee’s ability to successfully implement its future programme of work,
particularly with regard to the increase in the number of expert s involved in theongoing evaluations and the operational costs in the case of further membership. The
Committee also noted the statement by the representative of Indonesia and welcomed
the ongoing commitment of Indonesia to the Committee’s work and outrea chactivities in that country.
43. The Scientific Committee acknowledged the significant effort of the Chair andsecretariat to conduct the sixty-seventh session and adopted a procedure for taking
decisions during the COVID-19 pandemic. The Committee also agreed to hold its
sixty-eighth session in Vienna from 21 to 25 June 2021, or, if required to be online,
an extension of the session duration will be considered, if necessary.

10 UNSCEAR 2020/2021 REPORT

Chapter III
Scientific reports
44. The following three scientific annexes were approved by the Committee at its
sixty-seventh session: (a) evaluation of medical exposure to ionizing radiation;(b) levels and effects of radiation exposure due to the accident at the Fukushima
Daiichi nuclear power station: implications of information published since the
UNSCEAR 2013 report; and (c) biological mechanisms relevant for the inference ofcancer risks from low-dose and low-dose-rate radiation.

A.

Evaluation of medical exposure to ionizing radiation
45. The Scientific Committee expresses its gratitude to the expert group which
conducted the evaluation of medical exposure to ionizing radiation and to delegations
for the technical discussions on this subject. The Committee also expresses its
gratitude to the national contact persons and the national experts who were involvedin collecting, submitting and checking the national data. Without reliable nationaldata, it would not have been possible to conduct the evaluation. The Committeeemphasizes that Member States’ efforts are needed in the future to maintain andfurther extend the UNSCEAR network of national contact persons and improvereporting of medical exposure data for enhanced quality and reliability of futureevaluations of sources and levels of exposure to ionizing radiation.
46. The Scientific Committee has considered the results of the evaluation of medical
exposure in the light of its past UNSCEAR 2008 report 12 and has reached thefollowing conclusions contained in paragraphs 47–53 below.
47. Medical exposure remains by far the largest human-made source of radiation
exposure of the population. In the period 2009–2018, about 4.2 billion medical
radiological examinations were performed annually. The collective effective dose wasestimated to be 4.2 million man sieverts (man Sv) for the global population of
7.3 billion people, resulting in an effective dose per caput of 0.57 mSv (excluding
radiotherapy). In addition, an estimated 6.2 million courses of radiation therapy
treatment were performed each year, about 5.8 million by external beams and
0.4 million by brachytherapy. An estimated 1.4 million radionuclide therapy
treatments were performed each year. Doses from radionuclide therapy and radiation
therapy treatments were not included in the global estimate of collective effective
dose, because effective dose is not an appropriate measure for these types ofprocedures. Uncertainties in the overall number of examinations and in the collective
effective dose were estimated at ±30 per cent. The main sources of uncertainty were
the gaps in the knowledge of both the number of examinations and the dose per
examination, especially where no data were provided and modelled estimates wereused instead, and the variations in dose per procedure both within and between
countries.
48. The estimated annual effective dose per caput from medical radiologicalexaminations has fallen slightly compared with the Committee’s previous UNSCEAR
2008 report (from 0.65 to 0.57 mSv). The difference is, however, within the boundsof the estimated uncertainty. This trend stands in contrast to the trends observed in
the previous two UNSCEAR reports, which showed notable increases (see figure I).

__________________
12

Sources and Effects of Ionizing Radiation: United Nations Scientific Committee on the Effects ofAtomic Radiation 2008 Report to the General Assembly, vol. I (United Nations publication,2010), annexes A and B.

REPORT TO THE GENERAL ASSEMBLY 11

Figure I
Annual effective dose per caput from different UNSCEAR medical exposure
evaluations
0.7

0.65
0.57

Per caput effective dose
(mSv)

0.6
0.5
0.4

0.43
0.37

0.33

0.3
0.2
0.1
0

1988

1993

2000

2008

2020

As reported in the UNSCEAR reports for the years given

49. Conventional radiology (excluding dental examinations) accounts for 63 percent of procedures and 23 per cent of the collective effective dose. Dental radiology
accounts for 26 per cent of procedures, but only 0.2 per cent of the collective effective
dose. Computed tomography makes the largest contribution (about 62 per cent) to thecollective effective dose but accounts for only about 10 per cent of all procedures.
Interventional radiology accounts for only 0.6 per cent of all procedures but
contributes 8 per cent of the collective effective dose. Diagnostic nuclear medicine
accounts for about 1 per cent of all procedures and about 7 per cent of the collective
effective dose (see figure II).
Figure IIDistribution of (a) examinations/procedures by imaging modality and theircontribution to (b) the collective effective dose from medical exposures (excluding
radiotherapy)(a) Examinations/proceduresInterventional radiology, 0.6%
Computed tomography, 9.6%

Dental radiology,
26.3%

Diagnostic nuclear
medicine, 1.0%

Conventional
diagnostic
radiology(excluding
dental), 62.6%

12 UNSCEAR 2020/2021 REPORT(b) Collective effective dose
Diagnostic nuclear medicine, 7.2%
Interventional
radiology, 8.0%

Conventional
diagnostic radiology(excluding dental),
23.0%

Dental radiology,
0.2%

Computed tomography, 61.6%

50. The use of computed tomography has continued to expand and has replacedsome of the older radiography and fluoroscopy examinations. The total number ofcomputed tomography examinations has increased by about 80 per cent, and its
contribution to the collective effective dose has increased from 37 per cent to 62 per
cent. However, a major reduction has been reported in radiography and fluoroscopy
examinations of the gastrointestinal tract (about 90 per cent), as well as a reductionin fluoroscopy examinations of the biliary and urinary systems and of the chest region.
Overall, the number of conventional radiology examinations has decreased by 10 per
cent, and the collective effective dose has fallen by 60 per cent. The contribution ofinterventional radiology procedures has increased considerably and now accounts for
8 per cent of the collective effective dose (compared with 1 per cent in the previous
assessment), despite accounting for only 0.6 per cent of the total number ofprocedures. Nuclear medicine continues to account for about 1 per cent of allprocedures, and its contribution to the collective effective dose has risen from 5 percent to 7 per cent. The number of radionuclide therapy treatments is estimated to haveincreased by 60 per cent since the previous UNSCEAR report, while the number ofcourses of radiation therapy has increased by 22 per cent.
51. Table 1 below shows the breakdown of the annual number and frequency of
medical radiological examinations by the World Bank classification of income level s
and the associated annual collective effective dose and annual effective dose per caput.
Table 1
Estimated average annual per caput dose and annual collective effective dosefrom reported medical radiological examinations in the 2009–2018 period byincome level
Population(millions)

Number of
examinations(millions)

Frequency(per 1,000
population)

Annual per
caput dose(mSv)

Annual collective
effective dose
(1,000 man Sv)

High

1 149

1 852

1 612

1.71

1 966

Upper-middle

2 619

1 197

457

0.46

1 195

Lower-middle

2 882

1 044

362

0.31

902

Low

662

101

153

0.13

89

Global

7 312

4 194

574

0.57

4 152

Category byincome levela

Values have been rounded.

REPORT TO THE GENERAL ASSEMBLY 13

52. The use of medical radiation for diagnosis and therapy continues to be strongly
weighted towards high- and upper-middle-income countries. Those countries accountfor around 70 per cent of all medical radiological examinations and 75 per cent of thecollective effective dose. This disparity is even more noticeable in nuclear medicine,where high- and upper-middle-income countries account for over 90 per cent ofprocedures and more than 95 per cent of the collective effective dose. Access toradiation therapy is similarly concentrated, with around 95 per cent of all treatments
occurring in high- and upper-middle-income countries.
53. The Committee underlined that the compilation of a global assessment of
medical exposure was a complex task and relied on the collection of quality-assured
data from Member States. As national surveys of medical exposure require adequate
planning and significant time and resources, the Committee recommend s the use of
its survey questionnaires (especially the essential d ata sets) to collect suchinformation on a regular basis. Also, the Committee intend s to update its assessments
more often by focusing on the essential data.

B.

Levels and effects of radiation exposure due to the accident at the
Fukushima Daiichi nuclear power station: implications of
information published since the UNSCEAR 2013 report
54. The Scientific Committee has considered the implications of the significant
amount of relevant information that has been published since the UNSCEAR 2013
report and reached the following conclusions.

1.

The accident and the releases of radioactive material into the environment
55. The Fukushima Daiichi nuclear power station lies in Fukushima Prefecture of
the Tōhoku region in Japan. It is located about 230 km north-east of Tokyo on the east
coast of Japan. On 11 March 2011, an earthquake with a magnitude of 9.0 occurredalong the Japan Trench. The earthquake and the following tsunami triggered a severe
nuclear accident at the Fukushima Daiichi nuclear power station. The m easures takenby the Japanese authorities included immediate (pre-emptive) and late (deliberate)evacuation, sheltering in homes, restricting distribution and consumption ofcontaminated foodstuffs (milk, vegetables, grains, meat, fish, etc.) and water,
instructions to take stable iodine, and the remediation of affected areas. These actions
were supported by radiation surveys of people and places.
56. More recent estimates of the total releases to the atmosphere from the accident
using all the information now available remain consistent with the total release of 131I
being within the range of about 100 to about 500 PBq, and that of 137 Cs being within
the range of 6 to 20 PBq, namely the same ranges as estimated in the UNSCEAR 2013
report. About 20 per cent of the total release to the atmosphere was estimated to havebeen dispersed over land, and a substantial fraction of this was deposited on land; andabout 80 per cent was dispersed over, and deposited in, the Pacific Ocean. The
estimated releases of these radionuclides from the Fukushima Daiichi nuclear power
station accident (based on the averages of the ranges) were about 10 per cent ( 131I)
and 20 per cent ( 137 Cs) of the releases estimated for the Chernobyl accident.
57. There were also direct releases to the ocean (from leakage and deliberate releaseof water containing radionuclides) of about 10 to 20 PBq of 131 I and 3 to 6 PBq of137
Cs in the first one to three months after the accident, followed by lower amounts
thereafter.

2.

Levels in the environment and food
58. The Scientific Committee has evaluated the information on the transfers of
released radioactive material through the terrestrial, freshwater and marine
environments. Some of the more pertinent findings are:

14 UNSCEAR 2020/2021 REPORT(a) Measurements of 137 Cs in seawater around the Fukushima Daiichi nuclear
power station site, across the Pacific Ocean and in neighbouring seas showed rapid
dispersion and dilution of the released material in seawater and its general movement
eastwards. By 2012, the concentrations of 137 Cs, even in the coastal waters off the
Fukushima Daiichi nuclear power station site, were little above the levels prevailingbefore the accident;(b) Extensive monitoring programmes that began immediately after theaccident enabled timely restrictions to be applied to prevent the sale of foodstuffs
from areas where the radionuclide concentration exceeded provisional regulation
values and standard limits 13 established by the Government of Japan. The
radionuclide concentrations in most monitored foodstuffs have declined rapidly since
the accident. Since 2015, no samples of livestock and crop products and only a few
samples of monitored wild food and of freshwater and marine fish products have beenfound to exceed the limits established by the Government of Japan to apply as of
1 April 2012. It is noteworthy that the Japanese standard limit for caesium
radionuclides is an order of magnitude lower than the levels recommended by the
Codex Alimentarius Commission for the purpose of international trade.
3.

Dose assessment(a)Members of the public
59. Because of the availability of much more information than was available at thetime of the UNSCEAR 2013 report, the Scientific Committee has been able to makemore realistic and robust estimates of doses to members of the public, avoiding theneed for the conservative assumptions applied in its earlier assessment.
60. In updating its dose assessment, the Scientific Committee has chosen to rely, tothe extent possible, on measurements of ambient levels of radiation, as well as ofradioactive material in people and the environment.
61. The main changes and/or improvements in the approach adopted by the
Scientific Committee and their implications were as follows:(a) An improved estimate of the temporal pattern of releases to the atmosphere(the “source term”) derived from the totality of measurements in the environment wasused, together with an improved atmospheric transport, dispersion and deposition
model, to estimate the concentrations of radionuclides in the air, for which only
limited measurements were available; this resulted in a different spatial and temporal
pattern of concentrations of radionuclides in the air compared with those in the
UNSCEAR 2013 report;(b) A new, validated model was developed to estimate external doses fromradionuclides deposited on the ground based on extensive measurements of thevariation of dose rate over time in the conditions in Japan; this resulted in a moderateincrease in estimated external doses, typically by several tens of per cent comparedwith the UNSCEAR 2013 report, and a slower decrease in the dose rates with time;(c) Revised and improved modelling of inhalation and ingestion doses,
including more realistic factors and elements of data specific to the affecte d Japanese
population, resulted in decreases in some estimated doses. These changes resulted ina decrease in the estimated thyroid doses in the first year after the accident by a factor
of about two and a decrease in the estimated average doses from the i nhalation ofradionuclides by a factor of about two compared with the UNSCEAR 2013 report;__________________
13

The terms “provisional regulation value” and “standard limit” are those used in the English
version of handbooks providing information on the effects of the Fukushima Daiichi nuclear
power station accident published by the Radiation Health Management Division, Ministry of theEnvironment of the Government of Japan and the National Institute for Quantum andRadiological Science and Technology of Japan. The terms used in Japan may not correspondexactly with the Japanese translation of these terms.

REPORT TO THE GENERAL ASSEMBLY 15(d) Improved information about people’s actual diet, purchases andconsumption of food and drink in Japan was used as a basis for revised dose estimatesfrom ingested radionuclides. Over the longer term, the estimates were based on
measurements made over 45 years of radiocaesium in food products and the whole
diet in Japan from fallout from atmospheric nuclear weapons testing. These changes
have reduced the estimated doses received from ingestion of food and drinking waterby a factor of at least 10 compared with the UNSCEAR 2013 report.
62. Taken together, these changes led to a reduction in the estimated average dosesin the first year compared with the estimated doses in the UNSCEAR 2013 report forthe more highly exposed municipalities and groups of evacuees by a few tens of percent for effective doses and by up to about a factor of two for thyroid doses. The
general reduction in the current estimates of effective d oses in the first year comparedwith those in the UNSCEAR 2013 report are largely due to the more realistic andlower estimates of doses from ingestion, and consideration of specific conditions inJapan and the use of dose coefficients that are specific to the Japanese population.
However, estimated effective doses to adults over a lifetime remain similar to theestimated doses in the UNSCEAR 2013 report for many municipalities, but formunicipalities with higher doses the current estimates are higher (by u p to 30 percent). Over the longer term, those decreases in the estimated effective doses in thefirst year are counterbalanced by an increase in the estimated dose from external
exposure to deposited radionuclides.
63. Groups of evacuees were estimated to have received average effective doses in thefirst year of up to about 8 mSv and average absorbed doses to the thyroid of up to about
30 mGy. These doses are additional to those doses from natural sources of exposure that are
estimated to result in average effective doses to the Japanese population of around 2 mSv.
64. Residents of municipalities in Fukushima Prefecture were estimated to havereceived average effective doses in the first year of up to about 5 mSv and averageabsorbed doses to the thyroid of up to about 20 mGy. Average effective doses due tothe accident in the first year in other prefectures were estimated to be less than about
1 mSv and absorbed doses to the thyroid less than about 6 mGy. By 2021, annual
average effective doses were estimated to have declined to less than 0.5 mSv in areasthat were not evacuated, and, following remediation work and the lifting of evacuation
orders, to less than 1 mSv in areas that were evacuated. Average effective doses overa lifetime due to the accident were, in all municipalities and prefectures, estimated tobe less than 20 mSv; and were highest for residents of Fukushima Prefecture.
65. The Scientific Committee estimated the distributions of doses among individuals
within a municipality or prefecture, taking account of all major sources of uncertainty
and variability. In general, 90 per cent of the individuals in each population groupwere estimated to have received doses within a range from about three times lower
than the average dose to about three times higher.
66. The Scientific Committee’s estimates of radiation exposures in cou ntries
neighbouring or close to Japan have not changed: effective doses were less than
0.01 mSv.
67. While the uncertainties in the estimated doses remain large, the ScientificCommittee does not believe that further research is likely to reduce them significantly
or change the central estimates, except in specific circumstances (e.g., to take accountof better information on the efficacy of remediation).
(b)

Workers
68. Although the reported doses to workers as a result of the Fukushima Daiichi
nuclear power station accident have been subject to some revision since the
UNSCEAR 2013 report, the general findings of that report remain valid: the average
effective dose of the 21,135 workers involved in mitigation and other activities at the
Fukushima Daiichi nuclear power station site from March 2011 to the end of March2012 was about 13 mSv, while 174 workers (0.8 per cent) received doses of more than

16 UNSCEAR 2020/2021 REPORT

100 mSv. Annual effective doses have been considerably lower since April 2012, withaverage annual effective doses declining from about 6 mSv in the year ending March2013 to 2.5 mSv in the year ending March 2019, and no individual has received anannual effective dose of more than 50 mSv since April 2013.
69. For the period March–December 2011, 1,757 workers (8.3 per cent) received
absorbed doses to the thyroid greater than 100 mGy, with an average dose for thisgroup of 370 mGy, and 13 workers were estimated to have received thyroid doses of
2 Gy or more.
70. A recent re-evaluation of the absorbed doses to the thyroid of the six workers
who received the highest doses has revealed that their absorbed doses to the thyroid,
estimated using individual-specific measurements of thyroid size, are, with one
exception, higher than previously reported (using population average thyro id size), in
one case by a factor of almost three. The highest assessed absorbed dose to the thyroid
due to internal exposure from inhalation of 131I is now 32 Gy. However, the Committee
believes that the absorbed doses to the thyroid reported in the UNSCE AR 2013 reportfor the workers as a whole remain valid because there is evidence indicating that themean thyroid volumes for adults in Japan do not differ significantly from the standard
reference values used in dosimetry.
4.

Health implications
71. In the years since the UNSCEAR 2013 report, no adverse health effects among
Fukushima residents have been documented that are directly attributable to radiation
exposure from the Fukushima Daiichi nuclear power station accident. The updated
estimates of doses to members of the public have either decreased or are comparablewith the Scientific Committee’s previous estimates. The Committee therefore
continues to consider that future health effects directly related to radiation exposure
are unlikely to be discernible. 14
72. Although approximately 200 cases of thyroid cancer have been detected by threerounds of screening among exposed children, the Scientific Committee believes that,on the balance of evidence, these cases are not the result of radiation exposure. Rat her,
their detection is the result of sensitive ultrasound screening procedures which havedetected cases of latent disease that would not have been diagnosed in the absence ofscreening, as has been observed in other populations without any increased radi ation
exposure. The Committee has assessed the incidence of thyroid cancer that could be
inferred from the estimated radiation exposures and has concluded that this is not
likely to be discernible in any of the age groups considered.
73. While the updated estimated doses to the red bone marrow have not increased,
the Scientific Committee’s estimate of leukaemia risk per mGy has increased
somewhat compared with what was stated in the UNSCEAR 2013 report. However,any increased incidence of leukaemia is still unlikely to be discernible among
Fukushima residents of any age. Likewise, the levels of exposure of members of the
public have been too low for the Committee to expect discernible increases in theincidence of breast cancer or other solid cancers.
74. There has been no evidence of excess congenital anomalies, stillbirths, preterm
deliveries or low birthweights among newborns related to radiation exposure. Increases
in the incidence of cardiovascular and metabolic conditions have been observed among
adults evacuated following the accident, but they are probably associated with__________________
14

As stated in the UNSCEAR 2013 report (annex A, appendix E), the Committee considers
quantitative and qualitative estimates of potential disease outcomes among the exposed
populations that may or may not be observable in future disease statistics. For the purpose of thisstudy, the Committee has also used the phrase “no discernible increase” where, although a diseaserisk in the longer term can be theoretically inferred on the basis of existing risk models, anincreased incidence of effects is unlikely in practice to be observed in future disease statistics
using currently available methods, because of the combination of the limited size of population
exposed and low exposures, i.e., consequences that are small relative to th e baseline risk and theiruncertainties.

REPORT TO THE GENERAL ASSEMBLY 17

concomitant social and lifestyle changes and are not attributable to radiation exposure.
Excess psychological distress also occurred in the aftermath of the combined
earthquake, tsunami and Fukushima Daiichi nuclear power station accident.
75. The health of the Fukushima Daiichi nuclear power station emergency workers
is being monitored in the nuclear emergency workers study sponsored by the Ministryof Health, Labour and Welfare of Japan. The majority of workers received effective
doses within the first year of less than 10 mSv, and only a small fraction of workers
received effective doses within the first year of 100 mSv or more. Thus, a discernible
increase in the incidence of leukaemia or solid cancers is unlikely. Approximately
1,750 workers received absorbed doses to the thyroid greater than 100 mGy, and13 workers received thyroid doses greater than 2 Gy. Because these thyroid doses
were received by adults rather than children, an excess of thyroid cancers in theworkers is also unlikely to be discernible.
5.

Radiation exposures and effects on non-human biota
76. The Scientific Committee continues to consider that regional impacts on wildlife
populations with a clear causal link to radiation exposure resulting from the
Fukushima Daiichi nuclear power station accident is unlikely, although detrimental
effects on individual organisms might have been possible. Indeed, various
cytogenetic, physiological and morphological (sublethal, individual -level) effects insome plants and animals have been observed in areas of enhanced radiation levels
following the Fukushima Daiichi nuclear power station accident, in the absence ofany reported wide-scale group impacts. In contrast, substantial population-level
impacts on biota were observed following the Chernobyl accident. A few studies haveindicated population impacts on selected wildlife groups following the Fukushima
accident. However no strong conclusions can be made from these studies, as there isalso radiobiological evidence to the contrary, and doubts remain about the robustnessof those findings, including uncertainty about reproducibility and control ofconfounding factors.

C.

Biological mechanisms relevant for the inference of cancer risks
from low-dose and low-dose-rate radiation
77. Since the establishment of the Scientific Committee in 1955, its mandate has
been to undertake broad estimates of the sources of ionizing radiation and its effects
on human health and the environment. In 1973, 15 the mandate was expanded toinclude scientific estimates of radiation risk. These assessments of the Committee
provide the scientific foundation used, inter alia, by the relevant agencies of theUnited Nations system in formulating international standards for the protection of thegeneral public and workers against ionizing radiation. 16 Those standards, in turn, arelinked to important legal and regulatory instruments. 17 In its 2012 report to theGeneral Assembly, the Committee considered the attribution of health effects and theinference of risks from radiation exposure, 18 as well as on the uncertainties in risk
estimates. The understanding of the biological mechanisms by which radiation -induced
effects such as cancer may occur is a relevant element for the inference of radiation
risk. This report is intended to synthesize the current k nowledge on biologicalmechanisms of radiation actions at doses mostly in the low to moderate range relevant
for cancer risk inference. It is emphasized that this is not a report on radiation effects;
in particular, it is not a report on cancers that can b e attributed to radiation exposure
situations.

__________________

General Assembly resolution 3154 (XXVIII).
The European Atomic Energy Community, FAO, IAEA, ILO, the International Maritime
Organization, NEA/OECD, PAHO, UNEP and WHO, “Fundamental safety principles: safety
fundamentals” (IAEA, Vienna, 2006), para. 1.6.
17Ibid., para. 1.5.
18
Official Records of the General Assembly, Sixty-seventh Session, Supplement No. 46 (A/67/46).
15
16

18 UNSCEAR 2020/2021 REPORT

78. In its annex on biological mechanisms relevant for the inference of cancer risks
from low-dose and low-dose-rate radiation, the Scientific Committee has undertaken
a comprehensive evaluation of the biological mechanisms that are considered tocontribute to or modulate carcinogenesis following radiation exposure, particularly at
low exposure levels (dose of 100 mGy and below for low-linear energy transfer(low-LET) radiation (X- and gamma-rays) and at dose rates of 0.1 mGy/min andbelow). The understanding of the mechanisms and modulators of carcinogenesis
following low-dose and low-dose-rate radiation exposures remains incomplete. An
appendix that considers principles and criteria for ensuring the quality of th e
Committee’s reviews of experimental studies of radiation exposure is included, which
serves as a companion to the “Principles and criteria for ensuring the quality of theCommittee’s reviews of epidemiological studies of radiation exposure” (annex A to
the UNSCEAR 2017 report). 19
79. There is very robust and reliable evidence that incomplete, failed or otherwise
dysfunctional responses to DNA damage contribute to induced mutation andchromosome damage and thereby affect the occurrence of cancers after exposu res at
all doses and dose rates studied. These responses relate to: (a) direct damage to DNA;and (b) damage attributable to the generation of reactive oxygen and related species,
both of which can contribute to double-strand breaks, complex lesions and effects on
mitochondria.
80.

The Scientific Committee concluded the following:(a) There are limited robust data that can be identified at this time that would
prompt the need to change the current approach taken for low -dose radiation cancer
risk inference as used for radiation protection purposes and in consideration of theallocation of resources in health-care settings, as well as for the purpose ofcomparison with other risks. The potential contributions of phenomena such astransmissible genomic instability, bystander phenomena, induction of abscopal effects
and adaptive response remain unclear. The dose-response relationships for mutations
and micronuclei are linear in form in the low-dose region down to at least 50 and
10 mGy low-LET radiation, respectively. Similarly, the dose-response for DNA
damage response activation is best represented by a linear form down to 10 mGy
low-LET radiation. It is notable that since the Committee’s last major evaluation ofcontributory mechanisms for radiation oncogenesis (UNSCEAR 1993 report), 20 there
have been substantial new data on low-dose and low-dose-rate radiation risk fromepidemiological investigations, in particular of occupational and medical cohorts.
These studies have added to the epidemiological evidence underpinning low-dose andlow-dose-rate cancer risk estimation and are supported by the mechanistic findings inthis annex;(b) There remains good justification for the use of a non -threshold model forrisk inference for radiation protection purposes, giv en the present robust knowledge
on the role of mutation and chromosomal aberrations in carcinogenesis. However,there are ways that radiation could act that might lead to a re-evaluation of the use of
the Committee’s approach to inference of radiation canc er risks. Some experimental
animal studies indicate that low-dose and low-dose-rate exposures can shorten
lifespan and possibly increase tumour burdens, but others indicate the extension oflifespan and reduced tumour burdens. The Committee also noted that generally, there
is insufficient mechanistic understanding of these observations. This situation may be
improved if, for example, low-dose exposures were shown consistently andunequivocally to stimulate DNA damage response/repair, or immune responses
modulating cancer development; such a consistent evidence base has not been found__________________
19

Sources, Effects and Risks of Ionizing Radiation: United Nations Scientific Committee on the
Effects of Atomic Radiation 2017 Report to the General Assembly (United Nations publication,2018).
20
Sources and Effects of Ionizing Radiation: United Nations Scientific Committee on the Effects ofAtomic Radiation 1993 Report to the General Assembly (United Nations publication, 1994),
annex E.

REPORT TO THE GENERAL ASSEMBLY 19

in this review. In this case, some elements of risk reduction might have to be taken
into consideration alongside the established DNA damage – mutational damage andpotential promotional pathways. Other examples where additional evidence would
help the assessment of risk include the findings relating to the stimulation of tumour
vascularization by low-dose exposures, where there is greater consistency andcoherence of the available data. Stimulation of tumour vascularization would be
expected to serve to promote tumour development;(c) There is long-standing evidence that the number of mutational steps
required for leukaemia is less than in the case of solid cancers, and this im pacts on
the time to presentation of leukaemia by comparison with solid cancers.
81. As mentioned above, the implications of the studies on the induction oftransmissible genomic instability, bystander effects, abscopal effects and adaptive
responses are still not clear. Some studies suggest thresholds for the induction oftransmissible genomic instability and bystander effects at around 100 mGy low -LET
radiation; if confirmed, this would indicate that the phenomena are not relevant for
low-dose cancer risk inference. Adaptive response studies remain without a confirmed
mechanistic basis and are of mixed outcome; similarly, studies of samples frompersons inhabiting areas with high natural background radiation levels that areinterpreted by some as providing evidence for adaptive response are insufficiently
coherent to be adopted for risk assessment purposes.
82. Looking to the future, the recommended approach for combining a mechanistic
understanding of low-dose radiation carcinogenesis with epidemiological studies
is to use mathematical modelling integrating data from experimental systems(e.g., dose-response data for induction of key mutations or epimutations). For thispurpose, there exist good multistage model frameworks that have the flexibility toinclude data on somatic events and germline influences on risk. These approaches
may be used to test hypotheses and provide further insights for risk inference.
Consideration should be given to the use of adverse outcome pathway approaches, asapplied in chemical toxicology and risk assessment, to help define and formalize key
mechanistic steps in carcinogenesis following low-dose exposures. In addition,
experimental investigations may identify cancer risk indicators that, when validated,
could be integrated into epidemiological investigations to improve statistical poweror be used for population screening.

20 UNSCEAR 2020/2021 REPORTPart two
Report of the United Nations Scientific Committee on the
Effects of Atomic Radiation on its sixty-eighth session, held
online from 21 to 25 June 2021
Chapter IV
Introduction
83. Since the establishment of the United Nations Scientific Committee on
the Effects of Atomic Radiation (UNSCEAR) by the General Assembly in its
resolution 913 (X) of 3 December 1955, the mandate of the Committee ha s been toundertake broad assessments of the sources of ionizing radiation and its effects onhuman health and the environment. 21 In pursuit of its mandate, the Committee
thoroughly reviews and evaluates global and regional exposures to radiation. The
Committee also evaluates evidence of radiation-induced health effects in exposedgroups and advances in the understanding of the biological mechanisms, by whichradiation-induced effects on human health or on non-human biota can occur. Thoseassessments provide the scientific foundation used, inter alia, by the relevant agenciesof the United Nations system in formulating international standards for the protectionof the general public, workers and patients against ionizing radiation; 22 thosestandards, in turn, are linked to important legal and regulatory instruments.
84. Exposure to ionizing radiation arises from naturally occurring sources (such asradiation from outer space and radon gas emanating from rocks in the Earth) and fromsources with an artificial origin (such as medical diagnostic and therapeutic
procedures; radioactive material resulting from nuclear weapons testing; energy
generation, including by means of nuclear power; unplanned events such as thenuclear power station accidents at Chernobyl in April 1986 and that following thegreat east-Japan earthquake and tsunami of March 2011; and workplaces where there
may be increased exposure to artificial or naturally occurring sources of radiation).

__________________The United Nations Scientific Committee on the Effects of Atomic Radiation was established by
the General Assembly at its tenth session, in 1955. The terms of reference of the Committee areset out in Assembly resolution 913 (X). The Scientific Committee w as originally composed of
the following Member States: Argentina, Australia, Belgium, Brazil, Canada, Czechoslovakia(later succeeded by Slovakia), Egypt, France, India, Japan, Mexico, Sweden, Union of Soviet
Socialist Republics (later succeeded by the Russian Federation), United Kingdom of GreatBritain and Northern Ireland and United States of America. The membership of the ScientificCommittee was subsequently enlarged by the Assembly in its resolution 3154 C (XXVIII) of
14 December 1973 to include the Federal Republic of Germany (later succeeded by Germany),
Indonesia, Peru, Poland and the Sudan. By its resolution 41/62 B of 3 December 1986, theAssembly increased the membership of the Committee to 21 member s and invited China tobecome a member. In its resolution 66/70, the Assembly further enlarged the membership of theCommittee to 27 and invited Belarus, Finland, Pakistan, the Republic of Korea, Spain and Ukra ine
to become members.
22
For example, the international basic safety standards for radiation protection and safety ofradiation sources, currently co-sponsored by the European Commission, FAO, IAEA, ILO,
NEA/OECD, PAHO, UNEP and WHO.
21

REPORT TO THE GENERAL ASSEMBLY 21

Chapter V
Deliberations of the United Nations Scientific Committee on
the Effects of Atomic Radiation at its sixty-eighth session
85. The Scientific Committee held its sixty-eighth session online from 21 to 25 June
2021. 23 Due to the extended period of disruption to the Committee’s normal mode o foperation due to the COVID-19 pandemic, and the need to hold a second session
online, the Committee agreed to extend the term of the current officers of the Bureau
for one additional session. The following were elected as officers of the Committee
for its sixty-eighth session: Gillian Hirth (Australia) as Chair; Jing Chen (Canada),
Anna Friedl (Germany) and Jin Kyung Lee (Republic of Korea) as Vice -Chairs; andAnssi Auvinen (Finland) as Rapporteur.
86. The Scientific Committee acknowledged its sixty-fifth anniversary, and heard
statements of congratulations, support and appreciation from (a) the Executive
Director of UNEP, Inger Andersen, who congratulated the Committee on its sixty-fifth
anniversary and for its long contribution to protecting people and the environment, while
thanking the Committee for its hard work, and also acknowledged the long history ofengagement between UNEP and the Committee, which she hoped would continue and be
strengthened; (b) the Executive Director of the United Nations Office on Drugs and Crimeand Director-General of the United Nations Office at Vienna (UNOV), Ghada Fathi Waly,
who stated that UNOV was proud to support the Committee’s mission through the provisionof a range of administrative-, information technology- and procurement-related support; and(c) the Director General of IAEA, Rafael Mariano Grossi, who highlighted the cooperation
between IAEA and the Committee. He noted that it was the thirty-fifth year following
the Chernobyl accident and 10 years since the accident at the Fukushima Daiichi
nuclear power station, and that the work of IAEA and the assessments of UNSCEAR
provided international organizations and the countries concerned with high -quality
and scientifically rigorous conclusions and recommendations. He noted that the IAEA
International Basic Safety Standards for Protection against Ionizing Radiation and for
the Safety of Radiation Sources, in particular, rely on the comprehensive data
provided by UNSCEAR. The Committee welcomed those statements.
87. The Scientific Committee took note of and discussed a number of paragraphs ofGeneral Assembly resolution 75/91 on the effects of atomic radiation. The issues
raised and discussed by the Committee are reported below in chapter V, section E(“Administrative issues”).

A.

Completed evaluations
88. The Scientific Committee discussed one scientific annex and agreed on thefindings and requested that the scientific annex be published in the usual manner (seechapter VI), subject to the modifications agreed upon, and that the final adoption be
conducted using a silence procedure due to the COVID-19 pandemic, as thatprocedure had been adopted by the Committee for use at the sixty-eighth session.

__________________
23

The sixty-eighth session of the Scientific Committee was attended by observers for Algeria, Iran
(Islamic Republic of), Norway and the United Arab Emirates, in accordance with General
Assembly, resolution 75/91, para. 24, and the observers for the European Union, FAO, IAEA,
ILO, the International Agency for Research on Cancer, ICAO, ICRP, ICRU, NEA/OECD, thePreparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization, UNEP
and WHO.

22 UNSCEAR 2020/2021 REPORT

B.

Present programme of work

1.

Second primary cancer after radiotherapy
At the sixty-eighth session, the Scientific Committee discussed and further
clarified the structure and content of the evaluation of second primary cancer afterradiotherapy and recommended that the radiobiology section would not cover in detail
all mechanisms possibly involved in carcinogenesis after radiation exposure, sincethese were addressed in the UNSCEAR 2020 report, annex C, 24 but rather would focus
on issues relevant for cancer risk after radiotherapy. The Committee also clarified thatthe meta-analysis of second cancer risks after radiotherapy should be based on
absorbed organ doses after quality control of dosimetric data in the publications to beevaluated. The expert group on second primary cancer after radiotherapy is to provide
a first draft annex at the sixty-ninth session.
89.

2.

Epidemiological studies of radiation and cancer
90. At its sixty-eighth session, the Scientific Committee discussed the progress
report on cancer epidemiology and took note of an update of the workplan, which wasrevised due to circumstances associated with the COVID -19 pandemic. Submissionof the report for approval is now planned in 2025. The evaluations will be based on
the Committee’s principles and criteria for ensuring the quality of the Committee’s
reviews of epidemiological studies of radiation exposure and clearly distinguishbetween attribution of effects and inference of risks, as outlined in the UNSCEAR
2012 report. 25 The expert group will provide a first draft annex at the sixty -ninth
session.

3.

Public exposure to ionizing radiation from natural and other sources
91. At its sixty-eighth session, the Scientific Committee discussed the progress
report on public exposure and noted that 22 Member States and four internationalorganizations (European Commission, IAEA, the Nuclear Energy Agency of theOrganization for Economic Cooperation and Development (NEA/OECD) and theWorld Health Organization (WHO)) had participated as members and observers in theexpert group. The Committee recognized the progress made since the previous
session, suggested revisions to the structure and content of the draft scientific annex
and agreed the proposed schedule for completion of the appendix on quality criteria
for evaluating public exposure to ionizing radiation by 2022 and the annex by 2024.
The Committee requested for the sixty-ninth session in 2022 a progress report fromthe expert group on the work carried out, as well as an updated timetable forcompletion of the project.

4.

Implementation of the Committee’s strategy to improve collection, analysis anddissemination of data on radiation exposure, including consideration of theCommittee’s ad hoc working group on sources and exposure
92. The General Assembly encouraged the Scientific Committee in several
resolutions 26 to work towards continuing implementation of its strategy for
optimizing working arrangements for its scientific evaluations, which includes theestablishment of working groups with specific tasks. At its sixty-eighth session theCommittee agreed to continue the activities of the ad hoc working group on sourcesand exposure to ionizing radiation to support the advancement of the Committee’s
evaluation of public, occupational and medical exposures.
93. The Committee stressed the importance of motivating Member States to fully
participate in the UNSCEAR surveys by underscoring and communicating their__________________To be published.
Sources, Effects and Risks of Ionizing Radiation: United Nations Scientific Committee on the
Effects of Atomic Radiation 2012 Report to the General Assembly (United Nations publication, 2015).
26
General Assembly resolutions 71/89, 72/76, 73/261 and 74/81.
24
25

REPORT TO THE GENERAL ASSEMBLY 23

utility. The results of UNSCEAR surveys may benefit Member States in many ways,
including:(a) A better understanding of national and regional levels of radiation
exposures to the public, workers and patients;(b) Assisting in the development of national policies, strategies andprogrammes to manage exposures as appropriate;(c) Providing Member States with comparative information on their levels ofradiation exposure in relation to the global and regional levels and there by identify
challenges and priorities where improvements can be made;(d) Providing other national and international institutions with reliable
information that can be used in the development of recommendations on protection
and safety for processes and procedures that use ionizing radiation;(e) Providing data to the scientific community that can be used in research andthe development of training tools.
94. The Committee, through the ad hoc working group on sources and exposure, has
analysed progress since the sixty-seventh session and has collected feedback from theexpert groups on public, occupational and medical exposures. The findings from thefeedback survey, alongside lessons learned from previous surveys, have been used todevelop the following key recommendations to further improve future and ongoingdata collection, analysis and dissemination:(a) Formulation of a clear statement of assessment objectives and better
elucidation of the benefits to Member States to improve participation and ensure
adequate resources are directed to data collection;(b) Establishment of approaches and methodologies based on realistic
expectations of the data available, and documenting lessons learned from previous
evaluations;(c) Procedural improvements, with feedback checking at various stages, indata collection and exposure assessment;(d) Provision of adequate resources (i) to maintain the network of national
contact persons from the Member States and facilitate the coordination of thecollection and submission of exposure data from Member States on a more regularbasis, and (ii) to establish small expert groups to sustain the assessment process bymonitoring the literature, identifying changes in exposure situations or the uses ofradiation, identifying areas where updated evaluations are necessary and refining theapproach to be better prepared for the next updates on the global assessment;(e) The Committee’s outreach strategy should highlight the importance of theCommittee’s surveys and evaluations for understanding radiation exposure and therole they have in providing an up-to-date scientific basis to support the worldwide
radiation protection system.
95. In view of the fact that the recommendations elaborated by the ad hoc working
group on sources and exposure represent a modified approach to the data collection
and analysis process, the Committee extended the mandate of the ad hoc working
group until its sixty-ninth session in 2022 to support the implementation of theserecommendations. During this extended term, the ad hoc working group will continue
to monitor progress of the data collection in the public exposure project, consolidate
recommendations made at the sixty-seventh and sixty-eighth sessions, and present a
draft updated strategy for data collection, analysis and dissemination to theCommittee for consideration and endorsement at the sixty-ninth session in 2022.
5.

Implementation of public information and outreach strategy for 2020–2024
96. At its sixty-sixth session, the Scientific Committee adopted the public
information and outreach strategy for the period 2020 –2024 to guide the work of the24 UNSCEAR 2020/2021 REPORT

secretariat and the Committee in outreach and communication activities with different
stakeholders. The strategy complemented the outreach activities planned for the
UNSCEAR 2020 report, annex B. 27 At its sixty-seventh session the Committee noted
the progress report and acknowledged the postponement of outreach activities on the
update of the UNSCEAR 2013 report due to the COVID-19 situation and encouraged
close collaboration with international organizations to further promote theCommittee’s findings.
97. At its sixty-eighth session, the Scientific Committee noted the progress reportfrom the secretariat and provided feedback on the ongoing and planned future
outreach activities. The Committee also noted the updated outreach plan for planned
activities in Japan for October 2021 or the first quarter of 2022. The Committee
acknowledged the sixty-fifth anniversary of UNSCEAR and expressed support to thesecretariat to continue dissemination of the Committee’s work. The Committee noted
the new proposed initiatives (such as webinars when launching publication of a newreport, involvement of a public relation expert, translation of the UNEP booklet
Radiation: Effects and Sources and development materials for children andadolescents), including the need to update the UNSCEAR public information andoutreach strategy. The Committee proposed to discuss in mor e detail the new
information and outreach strategy to be considered beyond 2024 at its sixty -ninth
session in 2022 so that a new strategy can be launched in a timely manner. These
activities are currently being funded exclusively from the UNSCEAR general t rust
fund.

C.

Update on the Committee’s long-term strategic directions
98. At its sixty-sixth session, the Scientific Committee approved its long-term
strategic directions and plan for the period 2020–2024. That plan included thefollowing:(a) Establishing working groups focused on sources and exposure, and effects
and mechanisms;(b) Inviting, on an ad hoc basis, scientists from other States Members of theUnited Nations to participate in the Committee’s evaluations ;(c) Increasing the Committee’s efforts to present its evaluations andsummaries thereof in a manner that attracts readers without compromising scientificrigour and integrity;(d) While maintaining the lead in providing authoritative scientificevaluations to the General Assembly, liaising closely with other relevant international
bodies to avoid duplication of efforts.

(a) Establishing working groups focused on the areas of sources and exposure, andeffects and mechanisms
99. At its sixty-eighth session, the Scientific Committee prolonged the mandate ofboth the ad hoc working group on effects and mechanisms and the ad hoc working
group on sources and exposure to continue their activities until the Committee’s sixty ninth session in 2022. The prolongation of these groups would all ow for (a) the ad
hoc working group on effects and mechanisms to continue to support and monitor
progress in the implementation of the programme of work, to evaluate new scientificdevelopments relevant for the Committee and to work with the secretariat to preparea meeting on the use of radiation protection quantities and units in the Committee’sreport; and (b) the ad hoc working group on sources and exposure to update theCommittee’s strategy to improve the processes for collection, analysis anddissemination of data on radiation exposures of the public, patients and workers.
__________________
27

To be published.

REPORT TO THE GENERAL ASSEMBLY 25(b) Inviting, on an ad hoc basis, scientists from other States Members of the United
Nations to participate in evaluations regarding the above areas
100. The Scientific Committee noted that the secretariat and the Bureau had taken
steps to involve scientists from other States Members 28 of the United Nations in
supporting the secretariat in conducting ongoing evaluations. This is particularly
relevant for the ongoing evaluation of public exposure to ionizing radiation fromnatural and other sources.
(c) Increasing the Committee’s efforts to present its evaluations, and summaries
thereof, in a manner that attracts readers without compromising scientific rigour
and integrity
101. The Scientific Committee referred to the outreach activities reported inchapter V, section B.5 above.
(d) While maintaining its lead in providing authoritative scientific evaluations to theGeneral Assembly, liaising closely with other relevant international bodies toavoid duplication of efforts
102. The importance of the Scientific Committee’s findings in providin g thescientific evidence upon which decisions are made by the international community
and the safety standards are developed was also demonstrated in the period since thesixty-seventh session. The Committee noted that since 2020, UNSCEAR has been
participating as an observer of the IAEA Commission of Safety Standards and as amember of the Steering Committee of the Global Nuclear Safety and Security
Network of IAEA. The Committee continues to collaborate with IAEA and remains
an observer of the Emergency Preparedness and Response Standards Committee andRadiation Safety Standards Committee in the current 2021 –2023 cycle. UNSCEAR isalso cooperating with a number of other organizations, including ICRP, WHO, theInternational Agency for Research on Cancer, the Inter-Agency Committee on
Radiation Safety and IRPA, among others. In addition, the 2019 report of theSecretary-General highlighted the importance of the Committee’s work for thescientific evaluation of radiation exposure and the health effects of th e Chernobyl
accident. 29 The secretariat also attended the United Nations Inter-Agency Task Forceon Chernobyl event held on 23 April 2021 to commemorate the thirty -fifth
anniversary of the Chernobyl accident.
103. The Scientific Committee welcomed and supported the continued cooperationof the secretariat with the United Nations and other international organizations 30 witha view to promoting the Committee’s work and exploring synergies and joint activities
that would contribute to that work and support the collection and analysis of scientificdata. The Committee specifically acknowledged the ongoing development offramework agreements with the European Commission, IAEA and WHO andrequested the secretariat to report on this matter at its next session.

D.

Future programme of work
104. Since the sixty-fifth session, the ad hoc working group on effects andmechanisms has collected and analysed the experience of, and the lessons learned by,
the Scientific Committee in recent years and developed a draft future pro gramme ofwork for the period 2020–2024 that was approved by the Committee at its sixtyseventh session. The ad hoc working group also supported the Bureau and thesecretariat in monitoring progress on the current projects, evaluating new scientific__________________

Austria, Italy, Norway, Singapore and Switzerland.
See A/74/461.
30
For example, the European Commission, IACRS, IAEA, ICAO, ICRP, ICRU, the International
Radiation Protection Association, NEA/OECD and UNEP.
28
29

26 UNSCEAR 2020/2021 REPORT

developments between the sessions and preparing a proposal for a new evaluation for
consideration by the Committee.
105. As agreed at the sixty-seventh session, the Committee will start in 2021 anevaluation of diseases of the circulatory system resulting from radiat ion exposure. At
its sixty-eighth session, the Committee approved a project plan, developed by the ad
hoc working group on effects and mechanisms, to initiate in 2022 the evaluation ondiseases of the nervous system from radiation exposure. Furthermore, it was agreed
to begin preparation of a new future programme of work (2025 –2029) in 2022.
106. Recognizing the limitations of radiation protection quantities, the ScientificCommittee agreed to continue the use of the effective dose and collective effective
dose as simple and manageable quantities to allow recording and comparing
exposures to a variety of sources and under a variety of circumstances. However, it
recommended that all future reports using effective dose or collective effective dose
include a clear statement summarizing how the Committee intends to use thesequantities and which uses are not appropriate. When reporting effects andmechanisms, the Committee agreed that exposure quantities should be based on
absorbed doses in relevant organs and tissues.
107. The Scientific Committee recalled the Committee’s unique mandate within the
United Nations family and emphasized that the timely implementation of the
programme for the period 2020–2024, and beyond, depended on sufficient andreliable long-term resources being available in the secretariat and that obtaining
additional scientific expertise and support for the planned outreach and administrative
tasks was essential to ensuring the feasibility and timely delivery of the planned
programme of work. This is particularly relevant in view of delays due to the COVID 19 pandemic and proposed new activities related to data collection and analysis for
medical and occupational exposures. The Committee also noted that implementationof the proposed ongoing work related to the collection of data on radiation exposuresof the public, patients and workers required additional resources that the secretariat
needs at least one additional in-kind expert or temporary position post, for example,
either a United Nations volunteer, expert working as a non-reimbursable loan or ajunior professional officer working on implementing the Committee’s programme ofwork for the period 2020–2024 in the area of sources and exposure.
108. Further, the Scientific Committee took note with concern of the secretariat’s
need to use the general trust fund contributions for additional scientific expertise,outreach and administrative tasks related to the implementation of the Committee’s
programme of work. That is particularly relevant in view of maintaining andimproving the existing data collection system and network for medical andoccupational exposures, and the new data collection and evaluation for public
exposure to ionizing radiation that started in March 2021. The Committee will be able
to implement a range of initiatives to motivate Member States to participate in theseimportant surveys only if it is able to strengthen its approach to collection and analysis
of essential data on radiation exposure on a regular basis. Such initiatives would haveconsiderable benefit for the Member States, the Committee, internationalorganizations and other stakeholders. That intent will be realized only if the secretariat
can be assured of regular and sustainable resources that are not reliant on general trust
fund contributions. The Committee will consider those challenges when theimplementation of the Committee’s programme of work for the period 2020–2024 andthe initial preparations for the future programme of work for the period 2025 –2029
are discussed at the sixty-ninth session.
109. The Scientific Committee took note of the request of the Executive Director of
UNEP 31 for Member States to support the Committee’s work through the provision offinancial resources to the general trust fund. While the Committee welcomed thecontributions of three States members 32 of the Committee and the part-time in-kind__________________
31
32

See note verbale dated 12 February 2020.
Australia, Canada and Germany.

REPORT TO THE GENERAL ASSEMBLY 27

support provided by Canada since November 2020, it encouraged other Member
States to use the possibility to strengthen the secretariat’s capacity through regularvoluntary contributions to the UNSCEAR general trust fund and/or in -kind
contributions (either United Nations volunteers, experts working as non -reimbursableloans or junior professional officers).

E.

Administrative issues
110. The Scientific Committee took note of General Assembly resolution 75/91 on
the effects of atomic radiation, in which the Assembly:(a) Requested UNEP to continue, within existing resources, to service theCommittee and to disseminate its findings to Member States, the scientific community
and the public and to ensure that the administrative measures in place wereappropriate, including clear roles and responsibilities of the various actors, so that thesecretariat is able to adequately and efficiently service the Committee in a predictable
and sustainable manner and effectively facilitate the use of the invaluable expertise
offered to the Committee by its members in order that the Committee may discharge
the responsibilities and mandate entrusted to it by the General Assembly ;(b) Urged UNEP to ensure that future recruitment processes are conducted inan efficient, effective, timely and transparent manner;(c) Recalled that the establishment of the post of Deputy Secretary in 2019,
which upgraded the previous post of Scientific Officer, allowed for the deputizationof the Deputy Secretary as Secretary as appropriate and assisted in the avoidance ofdisruptions in staffing;(d) Noted that the appointment of a Deputy Secretary had not yet been
finalized due to the ongoing impact of the COVID-19 pandemic, and urged UNEP to
finalize that process as soon as possible so as to avoid further disruption to theimportant work of the secretariat and the Scientific Committee;(e) Requested the Secretary-General to strengthen support for the Committee
within existing resources, in particular with regard to the increase of operational costsin the case of a further increase in membership, and to report to the General Assemblyat its seventy-sixth session on those issues;(f) Recalled the procedure for the possible further increases in membership of
the Scientific Committee as adopted in paragraph 21 of General Assembly
resolution 73/261, pursuant to paragraph 19 of Assembly resolution 66/70.
111. In regard to the points in paragraph 110 (b), (c), (d) and (e) above, the ScientificCommittee’s normal operation had continued to be impacted by the COVID-19
pandemic. The Committee recalled that the position of Deputy Secretary had been
established in 2019 and noted that due to the COVID-19 pandemic the appointmentof an officer to the position of Deputy Secretary was delayed as a consequence of a
recruitment freeze for all regular budget-funded United Nations posts. However,while the Committee acknowledged this position had continued to be filled
temporarily, it expressed frustration that the freeze of recruitment of United Nations
regular budget posts had been lifted in February 2021 and yet the appointment of
an officer to the position of Deputy Secretary had still not been finalized before thesixty-eighth session.
112. In regard to the points in paragraph 110 (a), (b), (c), (d) and (e) above, theExecutive Director of UNEP, Ms. Andersen, acknowledged the delays with therecruitment of a Deputy Secretary for the Committee and informed the Committeethat the recruitment of the Deputy Secretary was under way, and gave her assurance
that UNEP would do everything within its power to support the Committee’s financial
and human resources. She also expressed appreciation for the contributions to the
UNSCEAR general trust fund that had been received from Australia, Canada andGermany since the last session in November 2020.

28 UNSCEAR 2020/2021 REPORT113. In considering the requests of the General Assembly and the statement from the
Executive Director of UNEP, the Committee strongly encouraged the finaliz ation of
the appointment to the post of Deputy Secretary as soon as possible. The Committee
expressed grave concerns about the delays in permanently filling the position of
Deputy Secretary, which continued to pose a threat to the continuity of the work of
the Committee. The Committee expressed concern that the budget of the UNSCEAR
secretariat for carrying out scientific evaluations continued to decrease on a year -byyear basis and remained at its lowest level in the past 10 years and that the UNSCEAR
general trust fund contributions were being increasingly relied upon to address thedecline in regular budget funds for the recruitment of consultants. The Committee
also expressed serious concern about the Committee’s ability to successfully
implement its planned programme of work in a timely manner, in particular withregard to the increased number of experts involved in the ongoing evaluations, theneed for enhanced data collection, outreach activities and the operational costs in thecase of an increased membership. The Committee again recalled the point inparagraph 110 (a) above and that UNEP had been requested by the General Assemblyto adequately and efficiently service the Committee in a predictable and sustainable
manner, and noted that regular funding allowed the full independence of theCommittee to be observed.
114. In regard to the point in paragraph 110 (f) above, the Scientific Committee
recalled the procedure for possible further increases in membership of the ScientificCommittee and discussed the advice to be provided to the General Assembly. The
advice from the Committee is summarized in the following paragraphs.
115. In preparing its advice to the General Assembly, the Scientific Committee heard
statements from the scientific representatives of the observer countries Algeria, Iran(the Islamic Republic of), Norway and the United Arab Emirates on their experiences
as observers of the Committee and on their continued ability and willingness tocontribute to the work of the Committee. The Permanent Mission of the Islamic
Republic of Iran had also submitted a note verbale prior to the sixty-eighth session
confirming the interest of the Islamic Republic of Iran in joining the Committee as amember.
116. The Scientific Committee gave due consideration to the degree of participationof the observer countries and to the other matters outlined in the Secretary -General’ssuggested framework of criteria and indicators for membership, as detailed in thereport of the Secretary General (A/66/524, para. 16).
117. The Scientific Committee recalled that it was established by the General
Assembly at its tenth session, in 1955. As set out in Assembly resolution 913 (X), theCommittee was originally composed of 15 member States. The membership of theCommittee was subsequently enlarged by the Assembly in its resolution 3154 C(XXVIII) of 14 December 1973 to include a further five member States. By its
resolution 41/62 B of 3 December 1986, the Assembly increased the membership of
the Committee to 21 members and invited China to become a member. In its
resolution 66/70 of 2011, the Assembly further enlarged the membership of theCommittee to 27 member States.
118. In 2018, in paragraph 21 of its resolution 73/261, the General Assembly adopted
admission procedures for any future increases in the membership of the Committee.
Paragraph 21 (e) of that resolution states that the General Assembly shall consider theadvice of the Scientific Committee with regard to the adoption of the observers asStates members of the Committee in the fourth year of attending the Committee’s
sessions as observers. The advice shall be based on due consideration of a fair degreeof participation in accordance with the Secretary-General’s suggested framework ofcriteria and indicators for membership. 33
119. The Scientific Committee considered the four observer States using the criteria
adopted by the General Assembly, referred to above, and the Committee__________________
33

A/66/524, para. 16.

REPORT TO THE GENERAL ASSEMBLY 29

acknowledged the consistent participation and contribution to its work by the
representatives and experts of each observer State, including contributions toevaluations and data collection throughout the past four years. The Committee notedthat the four observer States reflected the principle of equitable geographicaldistribution, and it expected that each State would continue to make a valuable
contribution to the Committee’s work, as members, as they had demonstrated
throughout the past four years as observers.
120. The Scientific Committee also reported in its report to the General Assembly 34
that it had heard presentations from the scientific representatives of the observerStates on their research programmes and potential contribution to the Committee’swork. The Committee noted that the contributions would enhance the United Nations
regional networks in Africa and Asia and support the Committee’s work on thecollection, analysis and dissemination of data on exposure and levels of ionizing
radiation and assist with mapping radionuclide concentrations in the environment, in
accordance with its long-term strategic directions.
121. In particular, the Scientific Committee noted that the four observer States had
been invited to attend, and their representatives had actively participated at, each of
the sixty-fifth to sixty-eighth sessions (2018–2021) of the Committee. All four
observer States submitted data to the Committee’s global surveys on medical andoccupational exposure, were participating in the ongoing global survey on public
exposure and had advertised the global surveys in their respective regions.
122. Accordingly, the Scientific Committee considered that the four observer States
had demonstrated their active participation and commitment to the work of theCommittee. Further, the Committee advised the General Assembly that, in its opinion,
all four observer States compared favourably against the framework of objective
criteria for membership, noting that Committee membership was ultimately to be adecision for the General Assembly. The Committee recalled paragraph 21 (g) of
Assembly resolution 73/261, which stated that any further increases in membershipwere to occur only after financial aspects were fully reviewed and if the secretariat of
the Scientific Committee was appropriately strengthened, in acc ordance withconclusions drawn in previous reports of the Secretary -General. 35
123. The Scientific Committee adopted a silence procedure for taking decisions during
the COVID-19 pandemic. The Committee agreed to hold its sixty-ninth session in
Vienna from 9 to 13 May 2022.

__________________
34
35

Official Records of the General Assembly, Seventy-third Session, Supplement No. 46 (A/73/46).
Including Assembly resolutions 63/478, 66/524 and 69/350.

30 UNSCEAR 2020/2021 REPORT

Chapter VI
Scientific report124. The scientific annex on the evaluation of occupational exposure to ionizing
radiation was approved by the Committee at its sixty-eighth session.

Evaluation of occupational exposure to ionizing radiation
125. The Scientific Committee has been collecting and evaluating sources and levelsof occupational exposure since 1975. Occupational exposure to ionizing radiation canoccur as a result of activities utilizing radiation or radioactive substances in industry,
medicine, education and research and can also occur when workers 36 are exposed tonatural sources of radiation. The Committee’s evaluations of worldwide occupational
exposure to ionizing radiation provide information relevant for policy - and decisionmaking regarding the safe use of radiation. The resulting dose distribu tions and trends
provide insight into the main sources and situations of exposure and information about
the main factors influencing exposures. The evaluations assist in identifying emerging
issues and may identify situations that should be subjected to mo re attention andscrutiny by different stakeholders.
126. The Scientific Committee has conducted evaluations of worldwide occupational
exposure levels and trends based on two sources: (a) data from the UNSCEAR Global
Survey of Occupational Radiation Exposure; and (b) reviews and analyses publishedin peer-reviewed literature. The evaluation of occupational exposure to ionizing
radiation by the Committee is based on the individual monitoring of workers or theirworkplaces and the recording of their exposure. Data on occupational radiation
exposure in Member States are generally collected in terms of effective dose as it isused for radiation protection purposes. Therefore, occupational exposure is expressedin operational terms like “effective dose” and “collective effective dose”. These are
the radiation protection quantities used by the international safety standards
established under the aegis of IAEA with the co-sponsorship of relevant international
intergovernmental organizations. 37
127. At its sixty-second session in 2015, the Scientific Committee recommended tostart work on the next UNSCEAR Global Survey of Occupational Radiation
Exposure. The Committee issued a global survey using the same structure as used forthe previous one on medical exposures, requesting Member States to appoint national
contact persons, promoting meetings to clarify uncertainties and facilitating datacollection in order to promote greater participation of the Member States. In addition,
efforts for greater geographical coverage of data from different countries and regionsof the world were made, in order to better assess and reduce uncertainties in theanalysis of exposures. Despite those efforts, the commitment of the Member States,
even those that are members of the Committee, was not at the desired level, thereby
delaying the evaluation and conclusion of the annex. The Committee noted that not
more than 57 Member States had submitted data for the UNSCEAR Global Survey ofOccupational Radiation Exposure.
128. In the scientific annex, the Scientific Committee has analysed new available
data up to 2014. The Committee expressed its gratitude to the expert group on
evaluation of occupational exposure to ionizing radiation and to the delegations forthe technical discussions on this very important subject. The Committee welcomed
the arrangements with the International Civil Aviation Organization (ICAO) which
resulted in the provision of data on aircrew by additional Member States and for__________________
36 An occupationally exposed worker is any person who is employed, whether full time, part timeor temporarily, by an employer and who has recognized rights and duties in relation to
occupational radiation protection.
37
IAEA, Radiation Protection and Safety of Radiation Sources: International Basic Safety
Standards – General Safety Requirements Part 3 (2014).

REPORT TO THE GENERAL ASSEMBLY 31

additional years. The Committee also expressed its appreciation to the Member States
and their national contact persons and experts who were involved in collecting,reporting and analysing the national data on occupational exposure in a broad rangeof sectors. Without reliable national data, it would not have been po ssible to conduct
the evaluation, perform worldwide extrapolation and identify trends. However, alimitation of the assessment is that the data submission rate remained low and the lackof data continues to be a serious issue in a number of job sectors and for a number of
exposure situations.
129. The Scientific Committee has considered the results of the evaluation on
occupational exposure in comparison with the results in its previous UNSCEAR 2000
report 38 and UNSCEAR 2008 report 39 and reached the following conclusions
contained in paragraphs 130–141 below.
130. The evaluation of the level of occupational radiation exposure has improved
substantially for certain occupational sectors, for example, the medical, mineral
extraction (including coal and uranium), nuclear fuel cycle and civilian aviation
sectors, as compared with the evaluation in the UNSCEAR 2008 report. Collaboration
with international organizations (e.g., IAEA, NEA/OECD and ICAO) is credited withmuch of this improvement because of the provision of additional information. The
responses from States members of the Committee and United Nations Member States
were marginally improved. In spite of these improvements, the overall number ofoccupationally exposed workers and their collective radiation exposure a reunderestimated for some occupational sectors due to limited data, and therefore theCommittee has provided the best estimates. Another challenge for evaluating thelevels of regional and global occupational exposure is to improve the consistency ofreported data as well as improving the representativeness of the data through theparticipation of more countries. Initiatives for future assessments should focus on
encouraging and supporting Member States to submit their available data .
131. The worldwide annual number of workers exposed to natural and human -madesources of ionizing radiation is estimated by the Committee to be approximately
24 million in the period 2010–2014. About 52 per cent of those were employed in the
sectors that involve exposure to natural sources of radiation and about 48 per centwere employed in sectors that involve exposure to human-made sources of radiation.
That total number of workers is a slight increase compared with the period 1995 –
1999, when the annual number estimated by the Committee was about 23 million
workers for both sources combined (see figure III).

__________________
38

Sources and Effects of Ionizing Radiation: United Nations Scientific Committee on the Effects ofAtomic Radiation 2000 Report to the General Assembly, vol. I (United Nations publication,2000).
39
Sources and Effects of Ionizing Radiation: United Nations Scientific Committee on the Effects ofAtomic Radiation 2008 Report to the General Assembly, vol. I (United Nations publication,2010).

32 UNSCEAR 2020/2021 REPORT

Figure III
Estimated annual number of workers exposed to radiation by source of exposure
14000

Number of workers (103)

12000
10000
8000
6000
4000
2000
0

1995–1999

2010–2014

Human-made sources

Natural sources132. For exposure to natural sources of radiation during the period 2010 –2014, theextraction and processing of coal and minerals other than coal and uranium accounted
for 94 per cent of the annual number of workers. About 12 million were employed inmining operations: 70 per cent in coal mining and 30 per cent in other mining
operations, excluding uranium mining. The estimated number of people employed incivilian aviation (who are mainly exposed to cosmic radiation) was
0.7 million. The annual collective effective dose for natural sources was about
24,300 man Sv (excluding oil and gas extraction and radon exposure in workplaces
other than mines due to lack of data).
133. The estimated worldwide annual number of monitored workers exposed tohuman-made sources increased to over 11.4 million in 2010–2014 compared with
about 10 million in the period 1995–1999. The medical sector dominated theworkforce exposed to human-made sources, accounting for about 80 per cent of thetotal. The average annual effective dose for the period 2010–2014 for all human-madesources was about 0.5 mSv, a substantial decrease from 1.7 mSv some 40 years ago,
and the average annual collective effective dose was about 5,500 man Sv (see table 2) .
Table 2Estimates of worldwide occupational exposure associated from human-madesources for the period 2010–2014
Number of monitored
workers (10 3 )aAnnual collective
effective dose(man Sv)

Weighted average annual
effective dose
(mSv)

760

485

0.6

Medical use

9 000

4 500

0.5

Industrial use

1 100

437

0.4

540

38

0.1

11 4005 460

0.5Sectors

Nuclear fuel cycle

Miscellaneous use
Totala

Values are rounded.

134. The worldwide average annual effective dose for all workers during the period
2010–2014 was estimated to be around 1.2 mSv – about two thirds of the value
estimated for the period 1995–1999. The annual effective dose was estimated to bearound 2.0 mSv for workers exposed to natural sources and 0.5 mSv for workers
exposed to human-made sources. In the period 1995–1999, the estimated annual
effective dose to workers exposed to natural sources was 2.7 mSv (excluding radon

REPORT TO THE GENERAL ASSEMBLY 33

exposure in workplaces other than mines), while the exposure from human-madesources remained at 0.5 mSv (see figure IV).
Figure IV
Estimated average annual effective dose of workers by radiation source (mSv)

Effective dose (mSv)

3
2.5
2
1.5
1
0.5
0

1995–1999
Human-made sources

2010–2014
Natural sources135. The values presented in this report for natural and human-made sources are
estimates because many Member States did not provide data. The estimates of theCommittee are based on a process of mathematical and statistical extrapolation using
the limited available data provided by the countries in response to the UNSCEAR
Global Survey of Occupational Radiation Exposure. However, for the first time, inthis report, uncertainty estimates for occupational exposures are provided tocharacterize the precision and accuracy of the reported estimates of number ofworkers, expressed as a range of the average annual effective dose, and the annual
collective effective dose. Occupational sectors with more data generally have anarrower range, clearly demonstrating the value of having more data, from morecountries, available for analysis.
136. Improvements for the period 2010–2014 were possible for several reasons,
including the cooperation of international organizations and use of improved
mathematical and statistical techniques. For example, ( a) the improvement in theestimation of crew exposure in civilian aviation was due to the detailed information
on worldwide air traffic and civilian aviation personnel provided by ICAO; ( b) the
improvement in the estimates for the subsectors of the nuclear fuel cycle was due toavailability of information from the Information System on Occupational Exposure
database (jointly maintained by IAEA and NEA/OECD), IAEA and the World Nuclear
Association; and (c) in the medical sector, improvements were due to use ofmathematical multivariable models with mathematical derivation of uncertainties .
137. While some improvements were possible, limited data received through the
UNSCEAR Global Survey of Occupational Radiation Exposure and the lack ofcorrelations between the data and available predictor variables resulted in the inability
to estimate the worldwide level of exposure for all subsectors. Relatively complete
data submission for the nuclear fuel cycle worker sectors and the reliability of thisinformation is well documented. The Committee noted that there was a likely
underestimation of the number of workers and estimated collective effective doses,
owing to the incomplete data submission for some occupational sectors for thereporting period. For most of the subsectors of the industrial sector, military,occupations involving exposure to radon and several subsectors of the nuclear fuelcycle, the reported data did not allow the Committee to make sufficiently robust
worldwide estimates, and this remains an area for the Committee’s future work.

34 UNSCEAR 2020/2021 REPORT138. Although the data received by the Committee from Member States for thisevaluation are limited, extensive new data have been reviewed for some sectors.
Essential data collection with a larger number and broader representation of Member
States (e.g., regions, income level) has been identified as a future area of work for theCommittee in order to reduce uncertainties, to allow the extrapolation of estimatedoccupational exposure for sectors with limited data (e.g., for gas and oil extraction,
exposure to radon in workplaces other than mines) and to enhance estimates of trends
in different work sectors. The Committee recommended the use of its occupationalquestionnaire to collect such information on a regular basis.
139. The Committee noted that reported data on the equivalent doses for the lens of
the eye and for the hands (skin dose) were limited. It is expected that for theCommittee’s next evaluation of occupational exposure, more countries will be in aposition to provide reliable data on this topic.
140. The current evaluation of occupational radiation exposure has not identified anygroup of workers receiving high annual effective doses due to implementation of newtechniques in using radiation sources. As the assessment of the worldwide
occupational exposure is a complex task, the Committee relies on the collection of
up-to-date data on occupational exposure from all States Members of the United
Nations and continued collaboration with international organizations .
141. The Committee highlighted the importance and the need for reporting from more
Member States in the future. Their participation will (a) maintain and extend theCommittee’s network of national contact persons, and ( b) enhance the quality,
representativeness and reliability of the Committee’s evaluations of sources and levelsof exposure to ionizing radiation.

REPORT TO THE GENERAL ASSEMBLY 35

Appendix I
Members of national delegations attending thesixty-fourth to sixty-eighth sessions of the United Nations
Scientific Committee on the Effects of Atomic Radiationin the preparation of its scientific reports
for 2020 and 2021
Argentina

A. J. González (Representative), D. Álvarez, A. Cánoba,
P. Carretto, M. Ermacora, M. di Giorgio

Australia

G. Hirth (Representative), C. Lawrence, S. Solomon,
P. Thomas, A. Wallace, I. Williams

BelarusA. Razhko (Representative), A. Stazharau (Representative),
S. Sychik (Representative), A. Aventisov, V. Drobyshevskaya,
A. Nikalayenka, L. Sheuchuk, V. Ternov

Belgium

H. Vanmarcke (Representative), S. Baatout, H. Bosmans,
F. Dekkers, H. Engels, F. Jamar, L. Mullenders, H. Slaper,
P. Smeesters, P. Willems

BrazilL. Vasconcellos de Sá (Representative), D. de Souza Santos,
P. Rocha Ferreira

CanadaJ. Chen (Representative), P. Thompson (Representative),
J. Burtt, D. Bracken Chambers, P. Demers, J. Gaskin, R. Lane,
K. Sauvé, B. Thériault, R. Wilkins

China

S. Liu (Representative), Z. Pan (Representative), L. Chen,
L. Dong, T. Fang, D. Huang, M. Huang, Z. Lei, Y. Li, X. Lin,
J. Liu, L. Liu, S. Liu, J. Mao, G. Song, Q. Sun, X. Xia, M. Xu,
S. Xu, D. Yang, F. Yang, L. Yuan, X. Wu, G. Zhou, P. Zhou

Egypt

M.A.M. Gomaa (Representative), W. M. Badawy(Representative), T. M. Morsi

Finland

A. Auvinen (Representative), S. Salomaa (Representative),
R. Bly, E. Salminen

FranceD. Laurier (Representative), L. Lebaron-Jacobs(Representative), J.-R. Jourdain (Representative), Y. Billarand,
V. Blideanu, J.-M. Bordy, S. Candéias, I. Clairand, J. Guillevic,
C. Huet, A. Isambert, D. Klokov, K. Leuraud, F. Ménétrier,
S. Roch-Lefevre, M. Simon-Cornu, M. Tirmarche

Germany

A. Friedl (Representative), P. Jacob (Representative),
S. Baechler, A. Böttger, L. Brualla, C. Engelhardt, C. Fournier,K. Gehrcke, U. Gerstmann, T. Jung, M. Kreuzer, R. Michel,
W.-U. Müller, C. Murith, W. Rühm, L. Walsh, W. Weiss,
D. Wollschlaeger, H. Zeeb

India

A. Vinod Kumar (Representative), K. S. Pradeepkumar(Representative), B. Das, A. Ghosh

Indonesia

N. R. Hidayati (Representative), E. Hiswara (Representative),
T. Handayani, D. H. Nugroho, T.B.M. Permata, H. Prasetio,
N. Rahajeng, I. Untara

Japan

M. Akashi (Representative), T. Nakano (Representative),
K. Akahane, S. Akiba, K. Furukawa, R. Kanda, I. Kawaguchi,
K. Kodama, M. Kowatari, K. Ozasa, S. Saigusa, K. Tani,
H. Yasuda, Y. Yonekura, S. Yoshinaga

36 UNSCEAR 2020/2021 REPORT

MexicoJ. Aguirre Gómez (Representative), M. Cuecuecha Juárez,R. F. Ortega

Pakistan

R. A. Khan (Representative)Peru

A. Lachos Dávila (Representative), B. García Gutérrez

PolandM. Waligórski (Representative), L. Dobrzyński, M. Janiak,
M. Kruszewski, P. Olko

Republic of Korea

H. S. Kim (Representative), B. S. Lee (Representative), J. Jang,
K.-W. Jang, M.-S. Jeong, U. Jung, J. K. Kang, B. S. Kim,
J.-I. Kim, M. Kim, H. Lee, J. K. Lee, R. Lee, E. K. Paik, J.Park,
S. W. Seo, K. M. Seong, M. C. Song, H. Yu

Russian Federation

A. Akleev (Representative), T. Azizova, S. Fesenko, S. Geraskin,
D. Ilyasov, V. Ivanov, L. Karpikova, S. Kiselev, D. Kononenko,
A. Koterov, A. Kryshev, E. Melikhova, S. Mikheenko,
S. Romanov, V. Romanov, S. Shinkarev, R. Takhauov,
V. Usoltsev, V. Uyba, P. Volkova

Slovakia

L. Auxtová (Representative), M. Berčíková, A. Ďurecová,
A. Froňka, K. Petrová, L. Tomášek

Spain

A. M. Hernández Álvarez (Representative), M. J. Muñoz
González (Representative), C. Álvarez García, J. M. Fernández
Soto, M. T. Macías Domínguez, J. C. Mora Cañadas,
M. Sánchez Sánchez, E. Vañó Carruana

Sudan

R.O.A. Alfaki (Representative), E.H.O. Bashier(Representative), A.M. Elamin Hassan, N. M. Hassan Suliman

SwedenE. Forssell-Aronsson (Representative), I. Lund
(Representative), A. Almén, A. Hägg P. Hofvander, A. Wojcik

UkraineD. Bazyka (Representative), V. Chumak, N. Gudzenko

United Kingdom ofGreat Britain andNorthern Ireland

S. Bouffler (Representative), A. Bexon, R. Wakeford, W. Zhang

United States ofAmerica

V. Holahan (Representative), A. Ansari, W. Bolch, H. Grogan,
N. Harley, B. Napier, D. Pawel, G. Woloschak

REPORT TO THE GENERAL ASSEMBLY 37

Appendix II
Scientific staff and consultants cooperating with theUnited Nations Scientific Committee on the Effects ofAtomic Radiation in the preparation of its scientificreports for 2020 and 2021
A. Aroua

M. Balonov

V. Berkovskyy

S. Candéias

L. Chipiga

M. Eidemüller

C. Estournel

G. Etherington

G. Frasch

B. Howard

G. Ibbott

H. Järvinen

N. Kelly

I. LundL. Mullenders

E. Nekolla

M. P. Hande

D. Rabelo de MeloE. Samara

R. Shore

P. Shrimpton

R. Smart

S. Solomon

G. Woloschak

Members of the Committee’s ad hoc working group on the effects of radiation
exposure and the biological mechanisms by which they occur at the
sixty-sixth to sixty-eighth sessions
A. Friedl, Chair (Germany)

A. Auvinen, Rapporteur (Finland)

J.-R. Jourdain (France)

L. Lebaron-Jacobs, Rapporteur (France)

K. Ozasa (Japan)

K. M. Seong (Republic of Korea)

A. Akleev (Russian Federation)

S. Bouffler (United Kingdom)

D. Pawel (United States)
Members of the Committee’s ad hoc working group on supporting theCommittee’s work on improving data collection, analysis and dissemination oflevels of radiological exposure at the sixty-sixth to sixty-eighth sessions
J. Chen, Chair (Canada)

A. Ansari, Rapporteur (United States)

P. Thomas (Australia)

L. Vasconcellos de Sá (Brazil)

U. Gerstmann (Germany)

A. Kryshev (Russian Federation)

S. Romanov (Russian Federation)

J. Al Suwaidi (United Arab Emirates)

A. Bexon (United Kingdom)

V. Holahan (United States)

Secretariat of the United Nations Scientific Committee on the Effects of Atomic
Radiation
B. Batandjieva-Metcalf (sixty-sixth to sixty-eighth sessions)M. J. Crick (sixty-fourth session)
F. Shannoun (sixty-fourth to sixty-eighth sessions)
E. Korneva (seconded)
Y. Shimizu (seconded)ANNEX A
EVALUATION OF MEDICAL EXPOSURE TOIONIZING RADIATIONCONTENTS
LIST OF ABBREVIATIONS...................................................................................................................................... 41
I.

INTRODUCTION.............................................................................................................................................. 43

II.

SCOPE AND OBJECTIVES OF ANALYSIS ................................................................................................... 43

III. METHODOLOGY AND SOURCES OF DATA ............................................................................................. 46
A. UNSCEAR Global Survey on Medical Exposure............................................................................. 46
B.

Literature review ................................................................................................................................... 46

C. Methodology for global assessment ............................................................................................... 50
IV. ASSESSMENT OF GLOBAL PRACTICE ....................................................................................................... 52
V. ANALYSIS OF FREQUENCY DATA .............................................................................................................. 57
A. Diagnostic radiology ............................................................................................................................ 57
B.

Interventional radiology ..................................................................................................................... 60

C. Nuclear medicine .................................................................................................................................. 61
D. Radiation therapy.................................................................................................................................. 63
VI. ANALYSIS OF DOSIMETRY DATA............................................................................................................... 64
A. Diagnostic radiology ............................................................................................................................ 65
B.

Interventional radiology ..................................................................................................................... 68

C. Nuclear medicine .................................................................................................................................. 70
VII. DISTRIBUTIONS BY AGE AND SEX ............................................................................................................. 73
VIII. TRENDS IN MEDICAL EXPOSURE ............................................................................................................... 74
IX. IMPLICATION FOR FUTURE ANALYSES .................................................................................................... 81
X. SUMMARY AND CONCLUSIONS ................................................................................................................ 84

40

UNSCEAR 2020/2021 REPORTACKNOWLEDGEMENTS........................................................................................................................................ 86
Members of Expert Group........................................................................................................................... 86
List of national contact persons and national experts contributed to UNSCEAR
Global Survey on Medical Exposure................................................................................................. 87
APPENDIX A. METHODOLOGY FOR GLOBAL ASSESSMENT OF MEDICAL EXPOSURE ........................ 91
APPENDIX B. LEVELS AND TRENDS OF EXPOSURE IN DIAGNOSTIC RADIOLOGY ............................. 125
APPENDIX C. LEVELS AND TRENDS OF EXPOSURE IN INTERVENTIONAL RADIOLOGY .................... 207
APPENDIX D. LEVELS AND TRENDS OF EXPOSURE IN NUCLEAR MEDICINE ....................................... 243
APPENDIX E. TRENDS IN USE OF RADIATION THERAPY ............................................................................ 295
REFERENCES .......................................................................................................................................................... 331

The attachments cited in this annex and its appendices are electronically available for download fromhttp://www.unscear.org/unscear/en/publications/2020_2021_1_Attachments.html
A-1 SOURCES AND ESTIMATION OF UNCERTAINTIES IN MEDICAL EXPOSURE
A-2 MODELS FOR ESTIMATION OF GLOBAL FREQUENCIES OF MEDICAL EXPOSURE
A-3 SUMMARY FOR MODELLING GLOBAL FREQUENCIES OF MEDICAL EXPOSURE
B-1 SUMMARY OF SURVEY DATA FOR DIAGNOSTIC RADIOLOGY
C-1 SUMMARY OF SURVEY DATA FOR INTERVENTIONAL RADIOLOGY
D-1 SUMMARY OF SURVEY DATA FOR NUCLEAR MEDICINE
E-1 SUMMARY OF SURVEY DATA FOR RADIATION THERAPYANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

LIST OF ABBREVIATIONSCBCTCone beam computed tomography

CT

Computed tomography

CTA

Computed tomography angiography

CTCA

Computed tomography coronary angiography

CTDIvol

Volume-weighted computed tomography dose index

DAP

Dose-area product

DIRAC

IAEA Directory of Radiotherapy Centres Database

DLP

Dose-length product

ECG

Electrocardiogram

EC DDM

European Commission Dose Data Med project

EPI-CT

Epidemiological study to quantify risks for paediatric computerized tomography

ERCP

Endoscopic retrograde cholangiopancreatography

ESD

Entrance surface dose

HCL

Health-care level

HDR

High dose rate

HERO

Health Economics in Radiation Oncology study

IAEA

International Atomic Energy Agency

ICRP

International Commission on Radiological Protection

IEC

International Electrotechnical Commission

IGRT

Image-guided radiation therapy

IMRT

Intensity-modulated radiation therapy

INCAPS

IAEA Nuclear Cardiology Protocols Cross-Sectional Study

IOMPInternational Organization for Medical Physics

IR

Interventional radiology

IVU

Intravenous urography

KAP

Kerma area product

LDR

Low dose rate

LSJ

Lumbosacral junction

MIRD

Medical Internal Radiation Dosimetry

MPI

Myocardial perfusion imaging

MRI

Magnetic resonance imaging

MSCTMulti-slice computed tomography

NCI

National Cancer Institute

41

42

UNSCEAR 2020/2021 REPORTNCRP

National Council on Radiation Protection and Measurements

NM

Nuclear medicine

NRPB

National Radiological Protection Board

NUMDAB

IAEA Nuclear Medicine Database

OECD

Organisation for Economic Co-operation and Development

PCI

Prophylactic cranial irradiation

PET

Positron emission tomography

PSMA

Prostate-specific membrane antigen

PTCA

Percutaneous transluminal coronary angioplasty

QI

Quality indices

SAFRAD

IAEA Safety in Radiological Procedures Database

SAFRON

IAEA Safety in Radiation Oncology Database

SPECT

Single photon emission computed tomography

TIPS

Transjugular intrahepatic portosystemic shunt

TOP 7

Top 7 nuclear medicine procedures contributing most to the collective doseTOP 20Top 20 radiological examinations contributing most to the collective dose

VMAT

Volumetric modulated arc therapy

UNSCEAR

United Nations Scientific Committee on the Effects of Atomic Radiation

WHO

World Health Organization

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

43

I. INTRODUCTION
1.
Medical exposure evaluations of the United Nations Scientific Committee on the Effects ofAtomic Radiation (UNSCEAR) have aimed to determine the annual frequencies of medical
examinations and procedures involving the use of ionizing radiation and their associated radiation doses
to patients. 1 Past reports of the Committee [U4, U5, U6, U7, U9] have encompassed exposure andpractice in diagnostic radiology, nuclear medicine and radiation therapy. Data have been analysed todeduce temporal trends, to evaluate the population dose due to medical exposure, and to identify the
major contributing procedures to the total collective dose to patients.
2.
The overall purpose of this annex is to assess the magnitude of the medical exposure of patients toionizing radiation worldwide since the UNSCEAR 2008 Report [U9], to determine the relative
contributions to dose from various modalities and procedures, and to assess trends. The annex does notassess the benefits or risks arising from medical exposure nor occupational exposure resulting fromwork involving the medical use of ionizing radiation.
3.
This annex presents a comprehensive, up-to-date review of medical exposure worldwide. The
review is based on an analysis of (a) the responses of United Nations Member States to the UNSCEAR
Global Survey on Medical Exposure 2 for the years 2009–2018, with a majority of data provided for theperiod 2014–2017, and on (b) a review of the published literature on medical exposure, also since the
UNSCEAR 2008 Report [U9]. The annex also presents estimates of the frequency (per 1,000 population)of diagnostic examinations and therapeutic medical procedures, and the associated radiation doses.
4.
Details of the methodology of the global assessment used are presented in appendix A, while
detailed results from the UNSCEAR Global Survey, and the comprehensive review of the publishedliterature are presented in appendices B to E.

II. SCOPE AND OBJECTIVES OF ANALYSIS
5.
Medical exposure covers: (a) exposure of patients as part of their medical diagnosis or treatment;(b) exposure of asymptomatic people as part of health screening programmes or individual healthassessment; and (c) exposure of healthy individuals or patients voluntarily participating in medical,
biomedical, diagnostic or therapeutic research programmes [I3]. The latter is not included in theevaluation as it is not part of exposure resulting from medical diagnosis or treatment.
6.
This evaluation considers four general categories of medical practice using ionizing radiation:(a) diagnostic radiology, including dental radiology and computed tomography; (b) image-guided
interventional procedures (interventional radiology); (c) nuclear medicine; and (d) radiation therapy.
The Committee further divided diagnostic radiology into subcategories for the purpose of deriving an
improved global assessment. More details are presented in section III. Doses from radiation therapy andradionuclide therapy are not included in the global estimate of collective effective dose as effective
1 The term “patient” refers only to those individuals undergoing radiological procedures with regard to medical exposure as
defined in the International Basic Safety Standards [I3].
2 “UNSCEAR Global Survey” is used throughout the document where possible (see also https://www.survey.unscear.org).

44

UNSCEAR 2020/2021 REPORT

dose is only suitable for use in the low to medium dose range, where stochastic effects predominate, notthe high dose range where tissue reactions become significant. However, frequencies of courses ofradiation therapy treatment and radionuclide therapy treatments are considered in the trend analyses.
The annex addresses mainly medical radiological imaging for the estimation of population doses fromionizing radiation; therefore, the use of non-ionizing radiation imaging such as magnetic resonanceimaging (MRI) is not included in the scope of this evaluation. The appendices present additional
supporting information on radiological equipment and associated medical staff. Uncertainties in theCommittee’s global estimate of medical exposure are also addressed. More detailed information on
uncertainties, the models tested, and data used in the evaluation are presented in electronic attachments.
7.
Diagnostic radiology generally refers to the analysis of images obtained using X-rays. These
include projection radiography (e.g., chest X-rays, mammography), images obtained using fluoroscopy(e.g., barium swallow, barium meal or barium enema examinations) and images obtained by devices
using computerized reconstruction techniques such as computed tomography (CT). Dental radiology isalso included in diagnostic radiology; however, for this analysis it was presented separately as it affects
the estimation of frequencies of radiological examinations.
8.
Interventional radiology refers to procedures where X-ray imaging is used to guide the placementof devices in the body to repair structures, excise or clear pathology, or otherwise treat disease. Suchprocedures may be performed by clinicians other than radiologists, such as cardiologists, orthopaedic
surgeons, gastroenterologists, urologists and vascular surgeons.
9.
Nuclear medicine procedures involve the introduction of unsealed radioactive substances into thebody, most commonly to obtain images that provide information on either structure or function of anorgan. The radioactive substance may be administered intravenously, orally or by inhalation. A
radionuclide is usually combined with a targeting chemical to form a radiopharmaceutical that will be
distributed in the body according to physical or chemical characteristics (e.g., a radionuclide
incorporated in a phosphate will localize in the bone, making a bone scan possible). Radiation emitted
from the body is analysed to produce diagnostic images. Less commonly, radionuclides areadministered to treat certain diseases such as hyperthyroidism, thyroid cancer, bone metastasis, primaryor metastatic liver cancer, lymphomas and neuroendocrine tumours.
10. Radiation therapy refers to the use of ionizing radiation produced by a sealed source or a radiation
generator to treat various diseases (usually cancer). Sometimes radiation therapy is referred to asradiation oncology; however, benign diseases may also be treated. Radiation therapy is delivered
through external beams of radiation (teletherapy) or by placing sealed radioactive sources in or near thetumour tissue (brachytherapy). External radiation beams may consist of high-energy X- or gamma rays,
electrons, protons, neutrons, or heavier charged particles. Gamma-ray beams are often produced byhigh-activity sources of 60Co while all other external radiation beams are produced by electricalequipment. Radiation therapy (especially teletherapy) for a particular patient is frequently delivered
over a course of several separate exposures (treatment fractions). Here, as in previous UNSCEAR
reports (e.g. [U9]), the global annual total number of treatment courses (radiation therapy treatments) is
estimated, rather than the number of treatment fractions. It is important to note that second
malignancies following radiation therapy are not included in the scope of this evaluation. However, theCommittee has commenced a specific evaluation dealing with the dosimetric, biological andepidemiological aspects pertaining to the risks of second primary cancer after radiation therapy.

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

11.

12.

45

The objectives of the evaluation are to:−Provide comprehensive global estimates of frequency and dose for medical exposure, and the
distribution by medical exposure categories, age, sex, and specified levels of health care andincome;−Evaluate the uncertainties in the estimates and identify gaps in the data coverage;−

Examine trends in practice and in the contributions to dose made by various techniques toderive benchmarks for comparison purposes and to manage exposure;−

Summarize supporting contextual evidence on devices and staff levels and associated trends;−

Identify emerging issues and areas for future research that may warrant more attention andscrutiny, including opportunities to improve future evaluations of global medical exposure.

These objectives were met by providing:−

Estimates of annual collective effective dose and associated annual effective dose per caput
from medical radiological imaging worldwide, with separate assessments in relation todiagnostic radiology, interventional radiology and nuclear medicine;−

Estimates of annual total numbers and associated frequencies (per 1,000 population) of
diagnostic radiology examinations, interventional radiology procedures, nuclear medicine
procedures and radiation therapy treatments;−

Evaluations of the uncertainties in the estimates of the numbers of examinations/procedures
and collective effective dose;−

Analyses of the distributions of common types of examinations/procedures in terms of age,sex, typical average doses and frequencies of examinations/procedures and the collective dose,
together with analysis of national/regional variations in practice;−

Analyses of temporal trends in frequency of examinations/procedures and dose across theperiodic results provided by the Committee’s global assessments of medical exposure;−

Identification of areas for future analysis and for consideration in improving future global
assessments of medical exposure.

13. The Committee previously addressed the subject of accidental exposure of patients, particularly in
relation to radiation therapy in its UNSCEAR 2008 Report [ U9]. Therefore, accidental exposure is outof the scope of this evaluation. Accidental exposure can occur in all types of medical use of ionizing
radiation, though the consequences of such exposure in radiation therapy are usually the most severe
due to the high doses involved. The International Atomic Energy Agency (IAEA) runs widespreadincident reporting and learning systems for tracking the frequency of incidents and for developing
improved practice to minimize the likelihood and consequence of such incidents: Safety in Radiological
Procedures (SAFRAD) and Safety in Radiation Oncology (SAFRON) databases record incidents and“near-miss” data anonymously [I4].

46

UNSCEAR 2020/2021 REPORTIII. METHODOLOGY AND SOURCES OF DATA
14. Evaluation of medical exposure consists in assessing the annual frequencies of the types of
examinations/procedures being undertaken and evaluating the radiation doses for each type. Annual
frequency and dose data are derived from two main sources: (a) the UNSCEAR Global Survey on
Medical Exposure and (b) the comprehensive peer-reviewed scientific literature, supplemented byreports from relevant national authorities within Member States of the United Nations.

A. UNSCEAR Global Survey on Medical Exposure
15. A detailed questionnaire was developed for the UNSCEAR Global Survey on Medical Exposure,which sought collection of all available national information concerning annual numbers of procedures
and measures of typical exposure (including effective dose and physical dose quantities, as discussed inappendix A), together with additional supporting information on national practice. In the case ofradiotherapeutic exposure, information was requested on the total prescribed absorbed dose to theplanning target volume over an entire course of treatment or the administered activity in the case ofradiopharmaceutical therapy.
16. To improve the efficacy of the UNSCEAR Global Survey, an online UNSCEAR platform wasdeveloped. The platform provides a structure to capture the data provided for the present and future
surveys. The UNSCEAR online platform is comprised of tools for (a) data collection via spreadsheets; (b)data processing and storage via a database; (c) data analysis via a specific module; and (d) data
descriptions to assist contributing countries via the user manual for the UNSCEAR Global Survey [U11].
17. The UNSCEAR Global Survey was launched in 2014. To encourage increased participation ofUnited Nations Member States and secure the collection of all available data, particularly fromcountries that could supply only less detailed information, a simplified version of the questionnaire wasintroduced in 2017 asking for essential data. The essential data included key indicators of practice:annual total numbers of examinations/procedures within each broad type of radiological discipline (alldiagnostic radiology with categorization into conventional radiology, dental radiology, interventional
radiology, and computed tomography separately), together with totals for broad types of equipment andstaffing levels. Similar information was sought in relation to nuclear medicine and radiation therapy.
The responses to the current survey cover the years 2009–2018, with a majority of data provided for theperiod 2014–2017.

B. Literature review
18. A comprehensive review of published literature related to medical exposure was conducted,
covering the period 2005–2018, with inclusion of additional relevant recent articles and reports.
Publications were deemed suitable for pre-screening if there was a match on one or more of thefollowing search terms: population dose, collective effective dose (medical), frequencies of
examinations, procedures or treatments (radiology, nuclear medicine and radiation therapy),

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

47

examination codes, patient dose and radiology, automatic dose management. Screening sought toidentify publications that might demonstrate changes and updates in practice since the previous
UNSCEAR 2008 Report [U9]. A total of 640 articles were identified for review, of which 373 wereassessed as meeting the criteria for inclusion in this evaluation.
19. Table 1 summarizes national or regional evaluations of medical exposure published since theprevious UNSCEAR 2008 Report [U9] representing the contributions of the main imaging categories tothe total frequencies (number of examination per 1,000 population) and to the population dose frommedical radiological imaging (collective effective dose). This also includes data focussing on the 20
examinations and procedures that contribute most to the overall collective dose (TOP 20), a
methodology developed by the European Commission Dose Data Med 1 project (EC DDM 1) [E3] andapplied in its follow-up project Dose Data Med 2 (EC DDM 2) [E5]. The published literature indicatesthat contributions of computed tomography to total frequencies are typically much lower than theircontribution to the total collective effective dose, while dental examinations typically make a highcontribution (up to 40%) to the total frequency of diagnostic examinations but less than 1% to the totalcollective effective dose from medical exposure. Interventional radiology is typically less than 1% of
the total frequency but the mean contribution to the total collective effective dose is ~8%.

48

Table 1. Evaluations of medical exposure for main imaging categories published since the UNSCEAR 2008 Report [U9]Year(period)

Country

Contributions to total frequencies (%) (including dental and NM whenpercentage is given separately)

Radiography

Fluoroscopy aAustraliab

2010

66.1

3.2

Bulgaria

2010

72.1

7.8

Finland2008

Finland2008

France2007

Francee

CT

IR

NM

Dental12

Fluoroscopy a

IR

NM

66.7

1.4

6.7c

[H6]

Dental

0.3

4.9c

15.7

9.6

7.1

0.4

0.5

19.1

28.6

0.3

43

7.2

2.1

[E5]

14.6

12.5

0.6d

54.2

12.5

6.3

[B19]

15.1

10.8

0.7

55.9

12.9

5.4

[E5]

26.1

0.2

58

5.5

10.2

[E10]

69.4

1

26.7

17.7

0.2

71.3

3.1

7.8

[D10]

39

5.1

0.5

0.5

63

24.7

10.1

0.6

1.6

2010

55.3

42.3

2.1

France

2012

54

33.8

10.4

0.5

1.3

Germany

2009

58.2

3.1

26.6

9

0.8

2.4

13.7

17.1

0.3

57.7

6.9

4.6

[E5]

Ireland2010-2013

68.5

0.9

23

5.7

0.9

1

10

3

<1

55

23

9

[O1]

Italy

2006

83

2

12

10

[C12]

Kenya

2011

94.3h

2.36

2013

85

1

f

Republic of Koreak

0.8

Radiography

CT

25.5

8
54.1

Conventional radiology

Reference

Conventional radiology

Contribution to population dose (%) (including dental and NM whenpercentage is given separately)

0.3

15

g

Luxembourg

2002

58.4

Norway2002

73.8

Romania

2012

73

8.4

Russian Federation

2015

95.6l

Slovenia

2011

q

Sudan

Switzerland

3.3
10.7

2.9

27.7

10.4

0.04
0.3
0.7

55.8h

4.9i

29.6

7.6

2.8

35.6
0.3

36
41

3.6j

53
50

[E11]

6

[K13]

9.7

[L3]

7.6

[S12]

59

[B25]

7

0.3

j

0.3

10

9

79

2

0.7

2.9

0.6m

0.2

36.7n

6.8

44.9

9.9o

92.8

1.5

5.1 (9.8)p

0.6

19

6

64

11 (4.8)p

[Z1]

2010

99

0.1

1

0.03

83

0.7

16

0.5

[S24]

2008

50.2

1.2

6

0.8

15.5

4.1

65.2

11.4

i

11.3

78

g

14.1

2.9

41.3

0.6

0.7

[G5]

1.7

3.8

[B6]

[E5]

UNSCEAR 2020/2021 REPORT

CT: Computed tomography; IR: Interventional radiology; NM: Nuclear medicine; PET: Positron emissions tomography; SPECT: Single photon emission computed tomography

CountryYear(period)

Contributions to total frequencies (%) (including dental and NM whenpercentage is given separately)

Radiography

Fluoroscopy a

DentalIR

NM

Conventional radiology
Radiography

Fluoroscopy a

Dental

CT

IR

2008

49.7

1.2

41.9

6

0.8r

15.3

4.6

0.7

67.6

11.9r

[S3]

Switzerland

2013

41.4

1.25

47.4

9.6

0.36

11.5

11

0.9

70.4

6.2

[L2]

Taiwan, Chinah

2008

15

7.4

2.1

1.8

15.9

3.5

0.2

50.8

16.2

13.6

[C6]

United Kingdom

2008

61.5

2.3

27

7.3

0.7

11.1

14.1

9.4

0.4

63.5

7.1

5.9

[E5]

2009-2012

97n

2.3

0.7 (1.3)p

0.03

73.3n

20.9

5.3

0.5 (0.2)p

17

4

5

0.3s

49

14

26

[N1]

10

1

2

2

59

9

17

[N2]

52

8

5

[B20]

United States
United States

73.7

2006
k,t

2016
2007-2010

74
39

1

46

11
8

4

22u

13

49

Fluoroscopy includes angiography examinations (e.g., coronary angiography).
TOP 20 assessment, data for extremity radiography and dental radiography not included.
cExcluding contribution from PET examinations.
dDental procedures were not included in the calculation of the other percentages.
ePaediatric examinations only.
f
Emilia-Romagna region.
gComputed radiography only.
hProportion of mammography: 0.38% frequency and dose.
iExcluding angiographies.
jIncluding angiographies.
kCalculation with ICRP 103 tissue weighting factors [I11].
l
Includes chest screening 31.9%.
m
Includes angiography and “other”.
nIncludes chest fluorography for tuberculosis screening as the most frequently performed type of X-ray examination, whereas it is not performed on a routine basis in other European countries.
oIncludes chest screening 9.6%.
pExtrapolated value, TOP 20 value in parenthesis when differs from original values.
qData not available for dental examinations and nuclear medicine procedures.
r
Diagnostic and therapeutic interventional procedures.
s
Dental bitewing and full-mouth procedures only.
t
Data re-categorized (PET/CT and SPECT/CT moved to NM, gastrointestinal tract, urogenital and diagnostic coronary angiography moved to fluoroscopy).
u
Includes dental procedures.

[S22]

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

Europe (36 countries)b

NM

Switzerland

UkraineaCT

Reference

Conventional radiology

Contribution to population dose (%) (including dental and NM whenpercentage is given separately)

50

UNSCEAR 2020/2021 REPORT

C. Methodology for global assessment
20. In previous UNSCEAR reports (e.g. [U9]), annual frequency data on procedures were stratified
by health-care level (HCL) I, II, III or IV, according to the number of physicians per head of population(see also appendix A). The number of physicians had previously been shown to correlate well with thenumber of medical radiological examinations [M7]. The health-care levels are defined as (a) HCL I:>1 physician per 1,000 population; (b) HCL II: 0.334–1 physician per 1,000 population; (c) HCL III:
0.1–0.333 physician per1,000 population; and (d) HCL IV: <0.1 physician per 1,000 population.
Previous global estimates were derived by determining both the population-weighted averagefrequencies for procedures and the population-weighted average dose per procedure within each healthcare level and then extrapolating these population-weighted averages to the whole population withineach health-care level. This approach worked well when the world population was relatively evenly
distributed throughout health-care levels and when sufficient, representative data could be obtained foreach level. In the present assessment, however, 53% of the total world population is in countries
categorized as HCL I and very few data have been received from countries in other health-care levels.
21. An alternative to classification by health-care level is to use income classifications for countries
as published by the World Bank [F3]. The World Bank income classification also comprises fourlevels: high, upper middle, lower middle and low. It is based on gross national income per capita valued
annually in US dollars using a three-year average exchange rate. Cut-off points between classifications
are fixed in real terms; they are adjusted each year in line with price inflation. The distribution of the
global population using these levels (16%, 36%, 39% and 9%, respectively) is more even than is thecase for HCLs I–IV (53%, 31%, 9% and 7%, respectively). Another advantage of using the World Bank
classification is the possibility of comparing medical exposure with other health indicators as the World
Health Organization (WHO) uses the same classification.
22. Assessment within particular classifications can be expected to yield good results when practicewithin a classification is relatively consistent. An alternative is to construct a mathematical model of theobserved variation and use the model to predict practice in countries that have not supplied data. In thisassessment, mathematical models of procedure frequencies within seven broad modality categories
have been developed to generate projections for those countries that did not provide data to the
UNSCEAR Global Survey. The modality categories used hereby are conventional radiology (including
projection radiography without contrast, and radiography and fluoroscopy with contrast, but excluding
dental radiology), dental radiology, computed tomography, interventional radiology, diagnostic nuclear
medicine, radionuclide therapy and radiation therapy (figure I). While it would be desirable to include
population demographics in such models to account for possible variations in procedure frequencies
due to different age and sex distributions, it was not possible to adopt such an approach as only alimited number of countries were able to provide examination/ procedure counts with detailed age andsex distributions.

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

51

Figure I. Modality categorization scheme used for UNSCEAR medical exposure global assessmenta

Not part of the collective effective dose assessment because such therapeutic doses are intentionally high enough to cause
deterministic effects, however, included in the frequency trend analyses.

b

Mostly with contrast media.

cWithout contrast media.

dAnalysed separately for the global assessment.

23. Diagnostic radiology was divided into the two main subcategories of conventional radiology andcomputed tomography. In the UNSCEAR Global Survey, dental radiology was included as acomponent of projection radiography within conventional radiology (figure I), but it was treated as aseparate category in the assessment because it typically makes a major contribution to the total numberof examinations but usually only a very small contribution to the collective dose. In contrast, thecontribution of computed tomography to the total number of examinations was typically low but thecollective dose may be high. The category of conventional radiology (excluding dental) typically makes
the largest contribution to the total number of examinations/procedures.
24. For this assessment, interventional radiology procedures included minimally invasive procedures
performed under fluoroscopy guidance with therapeutic purpose for any cerebral, cardiac, pulmonary,
hepatobiliary, gastrointestinal, genitourinary, musculoskeletal and central nervous system diseases.
Other minimally invasive procedures performed under fluoroscopy guidance with diagnostic purpose
were included in the subcategory conventional radiology as part of radiography and fluoroscopy(mostly with contrast media).
25. Many nuclear medicine imaging procedures are now performed using hybrid systems such asSingle photon emission computed tomography with a CT component (SPECT/CT) or Positron emission
tomography with a CT component (PET/CT). For this assessment the CT component was considered to
be an integral part of the total nuclear medicine procedure, thus, the CT radiation dose has been added
to the dose resulting from the radiopharmaceutical to estimate a total dose per nuclear medicine
procedure. Such CT components were not included in the CT subcategory of diagnostic radiology.
26. For this assessment, a continuous mathematical model, in the form of a power function of thephysician density (all physicians per 1,000 population) in each country, was selected and applied foreach medical exposure category. This choice was motivated by the availability of the physician density
data, as WHO regularly publishes such values provided by its Member States, and the close relation to
the HCL model used in previous UNSCEAR evaluations [U4, U5, U6, U9]. More sophisticatedmodelling involving multiple parameters was also performed, however the results from the single

52

UNSCEAR 2020/2021 REPORT

parameter power function were generally preferred due to the simple interpretation, satisfactory
predictive power, and the wide availability of data. Further details of the methodology of the global
assessment of medical exposure and the models used are discussed in appendix A.
27. The global assessment of medical exposure was derived from the combination of (a) the
UNSCEAR Global Survey data, supplemented by literature data where this was available for countries
that did not provide a response to the survey, and (b) the results of the mathematical modelling(continuous model), and not from extrapolation of average frequency values within the HCL model asin previous UNSCEAR evaluations [U4, U5, U6, U9]. Uncertainties were assessed as standard
uncertainties [J8] for the estimated examination/procedure frequencies and the corresponding meandose values. Each uncertainty component is represented as a standard deviation and then combined into
an overall standard deviation (see also appendix A and electronic attachment A-1). The assessment
results are presented with breakdowns by health-care level and by income level to facilitate comparison
with past UNSCEAR evaluations and to provide data that may be useful in comparing trends over timeor between different countries or regions.

IV. ASSESSMENT OF GLOBAL PRACTICE
28. According to the UNSCEAR 2008 Report [U9], approximately 3.1 billion diagnostic radiology
examinations, 0.48 billion diagnostic dental examinations, 3.6 million interventional radiology
procedures, 33 million diagnostic nuclear medicine procedures, 5.1 million courses of radiation therapy
treatment, and 0.9 million radionuclide therapy treatments were undertaken annually worldwide. The
24% of the population living in HCL I countries received approximately two thirds of these
examinations.
29. Since the UNSCEAR 2008 Report [U9], there has been a major demographic shift (table 2) suchthat now more than 50% of the world population lives in HCL I countries. The principal reason for thisshift is the movement of several countries, notable among them Brazil and China, from HCL II to
HCL I. Nonetheless, there remains wide variation in health-care services and access to them withinthese broad groupings, and while large countries may meet the criterion for HCL I as a whole, many
regions within them would rank at lower health-care levels. Therefore, this evaluation seeks to model
the variation, rather than apply average values across whole health-care levels.
Table 2. Comparison of current world population distribution by health-care level with UNSCEAR
2008 Report [U9]UNSCEAR 2008 a(millions)

Proportion(%)

Current evaluation a(millions)

Proportion
(%)

I

1 540

24

3 908

53

II

3 153

49

2 256

31

III

1 009

16

622

9

IV

744

11

526

7

Total

6 446

100

7 312

100

Health-care level
categorya

Values are rounded.

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

53

30. In the period covered by this evaluation (2009–2018), the annual number of medical radiologicalexaminations/procedures, including diagnostic radiology, interventional radiology and nuclear
medicine, is estimated to be 4.2 billion, corresponding to an annual collective effective dose of
4.2 million man Sv (table 3). The standard uncertainty in both results is estimated to be ±15%. Taking
twice the standard uncertainty as an estimate of the overall uncertainty, the ranges for the total numberof examinations and the total collective effective dose are thus ±30% (table 4). The estimated collective
effective dose is approximately the same as for the previous assessment. As the global population has
increased (from 6.4 to 7.3 billion), the resulting annual per caput effective dose from medical exposure
has fallen slightly from 0.65 mSv in the UNSCEAR 2008 Report [U9] to 0.57 mSv, however thedifference is within the bounds of the associated uncertainties. Uncertainties were not derived for theprevious assessment, however the survey data in that case covered only 10–30% of the total world
population in contrast to the 40–60% of the world population covered by the current UNSCEAR Global
Survey (see also appendix A). It is therefore estimated that uncertainties in the current assessment arelikely lower than in the previous UNSCEAR 2008 Report [U9]. In addition, there are an estimated
1.4 million therapeutic nuclear medicine treatments, and 6.2 million courses of radiation therapy
treatment delivered each year.
31. Table 3 shows a breakdown of the total annual collective effective dose from medical radiologicalexaminations/procedures, categorized by health-care level. Compared to the previous UNSCEAR 2008
Report [U9], the estimated annual per caput effective dose for HCL I has decreased markedly.
However, this change is due largely to the demographic changes mentioned above, with several
countries with large populations moving from HCL II to HCL I. Table 3 also shows the categorization
by World Bank income levels [F3]. The annual per caput effective dose for high-income countries
estimated in this assessment (1.71 mSv) is similar to the value for HCL I countries in the UNSCEAR
2008 Report [U9] (~2 mSv).
Table 3. Estimated annual per caput effective dose and annual collective effective dose frommedical radiological examinations/procedures (2009–2018) by health-care level and by income level
The estimates are based on a continuous mathematical model (physician density per country)
Category

Population(millions)

Annual per caput
effective dose(mSv) a,b

Frequency(per 1 000
population)

Number of
examinations/procedures (millions)

Annual collective
effective dose
(1 000 man Sv) a,b

Categorization by health-care level
I

3 908

0.83

823

3 216

3 263

II

2 256

0.34

369

833

774

III

622

0.14

173

108

88

IV

526

0.05

71

37

27

Categorization by income level
High

1 149

1.71

1 612

1 852

1 966

Upper middle

2 619

0.46

457

1 197

1 195

Lower middle

2 882

0.31

362

1 044

902

Low

662

0.13

153

101

89

Global

7 312

0.57

574

4 194

4 152

a

For the effective dose determination, ICRP 60 tissue weighting factors were applied [I9].

bValues are rounded; however extended precision has been preserved to illustrate differences.

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UNSCEAR 2020/2021 REPORT

32. The contribution of the various modality categories to the overall number of examinations/procedures and the collective effective dose is shown in table 4 and the relative proportions are shownin figure II. Conventional radiology (excluding dental) accounts for 62.6% of procedures and 23.0% of
the collective dose. Dental radiology accounts for 26.3% of procedures but only 0.2% of the overallcollective dose. Computed tomography makes the largest contribution (61.6%) to the overall collective
dose but accounts for only 9.6% of all procedures. Interventional radiology and diagnostic nuclear
medicine make small contributions (0.6% and 1%, respectively) to the number of procedures but
significant contributions (8% and 7.2%, respectively) to the overall collective dose.
33. The estimations presented in tables 3 and 4 were derived by applying a continuous model of theexamination frequencies as a function of the physician density (all physicians per 1,000 population) ineach country and using the model to estimate examination frequencies for countries that did not provide
data to the UNSCEAR Global Survey. Arithmetic mean doses per examination were determined fromthe survey data and applied to all countries that did not provide dose information to the survey.
Uncertainties for the total number of examinations were derived by combining the estimateduncertainties for examination counts included in country submissions to the survey with theuncertainties in the predictions of the continuous model. Uncertainties in the average doses per
examination were determined from the provided data and combined with the uncertainties for thenumbers of examinations to derive the uncertainty in the collective effective dose (see appendix A).
Table 4. Estimated annual number of medical radiological examinations/procedures (2009–2018)
and contribution to collective effective dose by modality categories
Estimates are based on a continuous mathematical model (physician density per country). Uncertainties are
expressed as 2-standard deviations
Modality categoryaExaminations/procedures(millions) a

Uncertainty(%)

Collective effective dose
(1 000 man Sv) a,b

Uncertainty(%)

Conventional radiology(excluding dental)

2 626

35

955

45

Dental radiology

1 101

60

10

70

Computed tomography

403

40

2 556

45

Interventional radiology

24

80

334

90

Diagnostic nuclear medicine

40

70

297

75

Radionuclide therapy

1.4

35

Not included

Radiation therapy c

6.2

25

Not included

Total

4 194

30

4 152

c

30

Values are rounded; however extended precision has been preserved to illustrate differences.

b

For the effective dose determination, ICRP 60 tissue weighting factors were applied [I9].

c

Not included in the total.

34. The collective dose estimates presented in tables 3 and 4 are based on effective dose determinedusing the tissue weighting factors from International Commission on Radiological Protection (ICRP)
Publication 60 [I9]. Table 5 presents a comparison between estimates based on the ICRP 60 tissue
weighting factors (E-60) and estimates based on the ICRP Publication 103 [I11] tissue weighting
factors (E-103). The estimated doses based on ICRP 103 tissue weighting factors were derived bymultiplying the mean doses per procedure by E-103/E-60 ratios taken from the literature [A6, A7, H5,

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55

S14, W1]. While this approach is not as accurate as a full evaluation of organ doses for each procedure
type, the impact of any additional uncertainty on the overall comparison is expected to be minor. Thechanges in the category totals when using the ICRP 103 weighting factors are quite small, except for
diagnostic nuclear medicine and dental radiology. The total collective effective dose for diagnostic
nuclear medicine is lower by 15% when using the ICRP 103 tissue weighting factors [I11], whereas thetotal collective effective dose for dental radiology rises by 88%. The dramatic rise for dental radiology
is due to the inclusion of the salivary glands, the extra-thoracic airways, and the oral mucosa in thetissue weighting scheme of ICRP 103 [L10]. The reduction in effective dose for diagnostic nuclear
medicine is largely due to changes in the reference computational phantom, rather than the changes intissue weighting factors [A6]. The overall collective dose for medical radiological examinations/procedures is lower by 1.6%. Similar results were found by the National Council on Radiation
Protection and Measurements (NCRP) in its recent evaluation of medical exposure in the United States[N2]. NCRP reported a 5% reduction in the collective dose from computed tomography, a 20%
reduction in the collective dose from nuclear medicine, and no change in the collective dose forradiography, fluoroscopy and interventional radiology. Doses for dental bitewing X-rays increased by
400%, while doses for full mouth series and panoramic X-rays increased by 200%. The overall
estimated collective dose was 5% lower when using the ICRP 103 [I11] compared to ICRP 60 [I9]tissue weighting factors.
Table 5. Comparison of estimated annual collective effective dose (2009–2018) by imaging modality
using ICRP 60 [I9] and ICRP 103 [I11] tissue weighting factorsaModality category

Collective doseICRP60(1 000 man Sv) a

Collective doseICRP103(1 000 man Sv) a

Variation (%)

Conventional radiology (excluding dental)

955

964

+0.9

Dental radiology

9.7

18.2

+88

Computed tomography

2 556

2 519

−1.5

Interventional radiology

334

332

−0.5

Diagnostic nuclear medicine

297

252

−15

Total

4 152

4 085

−1.6

Values are rounded; however extended precision has been preserved to illustrate differences.

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UNSCEAR 2020/2021 REPORT

Figure II. Relative contributions by modality category to (a) estimated annual number of
examinations/procedures and (b) estimated annual collective effective dose (2009–2018)

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57

V. ANALYSIS OF FREQUENCY DATA
35. The global assessment of medical exposure was derived from analysis of the data submitted to the
UNSCEAR Global Survey, supplemented with data from the published literature and national reports.
The survey included requests for essential information (total number of examinations/procedures forbroad survey modality categories); and responses containing this essential information were received
from 58 countries. Replies to the detailed questionnaire on examination frequencies and data onradiation dose for diagnostic radiology were received from 33 countries. Only 11 countries submitted
complete information including age and sex distribution by examination/procedure. Further,
54 countries provided information on nuclear medicine procedures and 51 countries on radiation
therapy treatments. While there were a large number of contributions to the UNSCEAR Global Survey
from HCL I countries, there were only few responses from HCL II–IV countries.

A. Diagnostic radiology
36. In extrapolating the data from the UNSCEAR Global Survey to derive a global estimate,diagnostic radiology was considered in three main subgroups: (a) conventional radiology (excluding
dental); (b) dental radiology; and (c) computed tomography. Detailed data on diagnostic radiology are
analysed and discussed in appendix B. Examination frequencies per 1,000 population for the threesubgroups were available from countries that submitted essential data to the UNSCEAR Global Survey,
as well as from countries that submitted more detailed data on the frequencies of specific examination
types. Survey data, supplemented with similar data on overall frequencies from the EC DDM 2 project[E5], from recent published literature (e.g., [K13, S24]), databases maintained by other internationalorganizations (e.g., IAEA, WHO), and from previous UNSCEAR reports [U6, U9] dealing withmedical exposure, were used in the analysis.

1.

Conventional radiology (excluding dental)

37. For conventional radiology (excluding dental), survey data from 43 countries were included in theevaluation. After inclusion of data from the EC DDM 2 project [E5] and from UNSCEAR reports [U6,U9], data from 65 countries, covering 48% of the total world population, contributed to the assessment.
38. The estimated total annual number of conventional radiography (excluding dental) examinations
is 2.63 billion, with an uncertainty of ±35%. The total estimate was derived by combining the assesseddata with the predictions of a continuous model for countries that did not submit data to the UNSCEAR
Global Survey. The continuous model was a power-law fit to the examination frequencies in theassessed data as a function of physician density (all physicians per 1,000 population). A detailed
summary is shown in table 6, with categorization by health-care level and by income level. The numberof examinations in the assessed data is summarized, along with the estimates using the continuous
model for the remaining countries, the resulting total and the overall average examination frequency.
The uncertainties stated by countries in their survey submissions and the uncertainties of the predictions
from the continuous model were combined to derive an uncertainty in the overall total estimate of±35%. Further details of the modelling methodology and related uncertainties are given in appendix A
and in electronic attachments A-1 to A-3.

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UNSCEAR 2020/2021 REPORT

39. The estimated annual total of 2.63 billion conventional radiology (excluding dental) examinations
is a reduction of 9% from the 2.87 billion examinations per annum estimated in the UNSCEAR 2008
Report [U9]. The global average annual frequency has decreased from 445 to 359 examinations per
1,000 population. These differences are within the bounds of the estimated uncertainties.
Table 6. Global estimate of number of conventional radiology (excluding dental) examinations perannum derived from assessed data (2009–2018) and predictions from continuous model
Category

Population(millions)Examinations
from assesseddata (millions) a

Examinations
from modelleddata (millions) a

Total number of
examinations(millions) a

Averageexaminations per
1 000 population

Categorization by health-care level
I

3 908

1 568

285

1 853

474

II

2 256

0.3

645

645

286

III

622

19

75

94

151

IV

526

0.04

34

34

65

Categorization by income level

a

High

1 149

961

22

983

855

Upper middle

2 619

539

225

764

292

Lower middle

2 882

87

714

801

278

Low

662

0.3

78

78

118

Global

7 312

1 587

1 039

2 626

359

Values are rounded; however extended precision has been preserved to illustrate differences.

2.

Dental radiology

40. UNSCEAR Global Survey data from 36 countries were included in the assessment for dental
radiology. After inclusion of data from the EC DDM 2 project [E5] and from UNSCEAR reports [U6,U9], data from 49 countries, covering 41% of the total world population, contributed to the assessment.
41. The estimated total annual number of dental radiology examinations is 1.1 billion, with anuncertainty of ±60%. The total estimate was derived by combining the assessed data with thepredictions of a continuous model for countries that did not submit data to the UNSCEAR Global
Survey. The continuous model was a power-law fit to the examination frequencies in the assessed data
as a function of physician density. Details of the modelling are discussed in appendix A. A detailed
summary is shown in table 7, with categorization by health-care level and by income level. The numberof examinations in the assessed data is shown, along with the estimated number predicted by thecontinuous model for the remaining countries, the resulting total number of estimated examination andthe overall average examination frequency per 1,000 population. The uncertainties stated by countries
in their survey submissions and the uncertainties of the predictions from the continuous model werecombined to derive an overall uncertainty of ±60%. Further details of the modelling methodology andrelated uncertainties are given in appendix A and in electronic attachments A-1 to A-3.

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59

42. The estimated annual total of 1.1 billion dental radiology examinations is an increase of 130%
from the 480 million examinations per annum estimated in the UNSCEAR report [U9]. The global
average frequency has increased from 74 to 151 examinations per 1,000 population per year.
Table 7. Global estimate of number of dental radiology examinations per annum derived fromassessed data (2009–2018) and predictions from continuous model
Category

Population(millions)Examinations
from assesseddata (millions) a

Examinations
from modelleddata (millions) a

Total number of
examinations(millions) a

Averageexaminations per
1 000 population

Categorization by health-care level
I

3 908

809

173

982

251

II

2 256

0.07

111

111

49

III

622

0

6.9

6.9

11

IV

526

0

1.1

1.1

2

Categorization by income level

a

High

1 149

628

16

644

561

Upper middle

2 619

164

125

289

110

Lower middle

2 882

17

137

154

53

Low

662

0

14

14

21

Global

7 312

809

292

1 101

151

Values are rounded; however extended precision has been preserved to illustrate differences.

3.

Computed tomography

43. UNSCEAR Global Survey data for computed tomography examinations were received from43 countries. Additional data on examination frequencies were obtained from the EC DDM 2 project[E5] and from data reported to the Organisation for Economic Co-operation and Development (OECD)[O3]. Further data, particularly for HCL III and HCL IV countries, were used from UNSCEAR reports[U6, U9]. The assessment included data from 69 countries, covering 48% of the total world population.
44. The estimated total annual number of computed tomography examinations is about 400 million,
with an uncertainty of ±40%. The total estimate was derived by combining the assessed data with thepredictions of a continuous model for countries that did not submit data to the UNSCEAR Global
Survey. The continuous model was a power-law fit to the examination frequencies in the assessed data
as a function of physician density. Details of the modelling are discussed in appendix A. A detailed
summary is presented in table 8 with categorization by health-care level and by income level. The
number of examinations in the assessed data is also presented, along with the estimated number
predicted by the continuous model for the remaining countries, the resulting total and the overall
average examination frequency. The uncertainties stated by countries in their survey submissions andthe uncertainties of the predictions from the continuous model were combined to derive an overall
uncertainty of ±40%. Further details of the modelling methodology and related uncertainties are given
in appendix A and in electronic attachments A-1 to A-3.

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UNSCEAR 2020/2021 REPORT

Table 8. Global estimate of number of computed tomography examinations per annum derived
from assessed data (2009–2018) and predictions from continuous model
Category

Population(millions) a

Examinations
from assesseddata (millions) a

Examinations
from modelleddata (millions) a

Total number of
examinations(millions) a

Averageexaminations per
1 000 population

Categorization by health-care level
I

3 908

278

46

324

83

II

2 256

0

70

70

31

III

622

0.5

6.5

7.0

11

IV

526

0.06

1.88

1.9

3.7

Categorization by income level

a

High

1 149

181

1.3

183

159

Upper middle

2 619

92.6

38.7

131

50

Lower middle

2 882

4.4

77

81

28

Low

662

0.01

7.8

7.8

12

Global

7 312

278

125

403

55

Values are rounded; however extended precision has been preserved to illustrate differences.

45. Computed tomography makes the largest contribution to the overall collective dose from medical
exposure, so uncertainties in the estimation of computed tomography examination frequencies are very
important. The assessed data includes 278 million examinations in HCL I countries, approximately
86% of the overall total estimate of examinations in that HCL category, implying a relatively robust
projection. The most critical point is the absence of survey data for HCL II, where the entire estimate of
70 million examinations derives from the modelling. Obtaining data on computed tomography scanningfrequency in HCL II countries is an important future goal to produce robust estimates of collective dosefrom medical exposure. Equivalently, in the categorization by income levels, the lack of data for lower
middle-income countries is the most significant source of uncertainty in the overall total estimate. Moredata from countries in the lower middle-income and low-income classifications would yield a better
estimate in the future. The estimated annual total of about 400 million computed tomography
examinations is an increase of 82% from the 220 million examinations per annum estimated in theprevious UNSCEAR assessment [U9]. The global average frequency has increased from 34 to 55
examinations per 1,000 population per year.

B. Interventional radiology
46. UNSCEAR Global Survey data were received from 39 countries. After inclusion of data from the
EC DDM 2 project [E5] and other sources, a total of 57 countries, covering 46% of the total world
population, contributed to the assessment.
47. The estimated total annual number of interventional radiology procedures is about 24 million,
with an uncertainty of ±80%. The total estimate was derived by combining the assessed data with thepredictions of a continuous model for countries that did not submit data to the UNSCEAR Global

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

61

Survey. The continuous model was a power-law fit to the procedure frequencies in the assessed data asa function of physician density. Details of the modelling are discussed in appendix A. A detailed
summary is presented in table 9 with categorization by health-care level and by income level. The
number of procedures in the assessed data is presented, along with the estimated number predicted by
the continuous model for the remaining countries, the resulting total and the overall average procedure
frequency. The uncertainties stated by countries in their survey submissions and the uncertainties of thepredictions from the continuous model were combined to derive an overall uncertainty of ±80%.
Further details are given in appendix A and in electronic attachments A-1 and A-2.
48. The estimated annual total of about 24 million interventional radiology procedures represents anapproximately sixfold increase from the 3.6 million procedures in the UNSCEAR 2008 Report [U9].
The annual global average frequency has increased from 0.6 to 3.2 procedures per 1,000 population.
This large increase is partly due to difficulties in making an appropriate comparison; other procedures(cerebral and vascular) were included in the previous UNSCEAR 2008 Report [U9], which are notincluded in the total interventional procedures of this evaluation as they are considered as diagnostic
and not therapeutic procedures (see also appendix C and electronic attachment C-1).
Table 9. Global estimate of number of interventional radiology procedures per annum derived fromassessed data (2009–2018) and predictions from continuous model
Category

Population(millions) a

Procedures fromassessed data
(millions) a

Procedures frommodelled data
(millions) a

Total number ofprocedures(millions) a

Averageprocedures per
1 000 population

Categorization by health-care level
I

3 908

16.5

2.8

19.3

4.9

II

2 256

0

3.9

3.9

1.7

III

622

0.01

0.3

0.31

0.5

IV

526

0

0.087

0.087

0.17

Categorization by income level

a

High

1 149

13.5

0.44

13.9

12

Upper middle

2 619

3.04

1.93

4.97

1.9

Lower middle

2 882

0.03

4.32

4.35

1.5

Low

662

0

0.44

0.44

0.7

Global

7 312

16.5

7.1

23.6

3.2

Values are rounded; however extended precision has been preserved to illustrate differences.

C. Nuclear medicine
49. The assessment for diagnostic nuclear medicine included UNSCEAR Global Survey data from46 countries. With data from the EC DDM 2 project [E5] and from two UNSCEAR reports [U6, U9],
data from 68 countries covering 52% of the total world population contributed to the assessment.
50. The estimated total annual number of diagnostic nuclear medicine procedures is 40 million, withan uncertainty of ±70%. The total estimate was derived by combining the assessed data with the

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UNSCEAR 2020/2021 REPORT

predictions of a continuous model for countries that did not submit data to the UNSCEAR Global
Survey. The continuous model was a power-law fit to the procedure frequencies in the assessed data asa function of physician density. Further details of the modelling methodology and related uncertainties
are given in appendix A and electronic attachments A-1 to A-3.
51. A detailed summary is shown in table 10 with categorization by health-care level and by income
level. The number of procedures in the assessed data is shown, along with the estimated number
predicted by the continuous model for the remaining countries, the resulting total and the overall
average procedure frequency. The uncertainties stated by countries in their survey submissions and theuncertainties of the predictions from the continuous model were combined to derive an overall
uncertainty of ±70%.
Table 10. Global estimate of number of diagnostic nuclear medicine procedures per annum derived
from assessed data (2009–2018) and predictions from continuous model
Category

Population(millions) a

Procedures fromassessed data
(millions) a

Procedures frommodelled data
(millions) a

Total number ofprocedures(millions) a

Averageprocedures per
1 000 population

Categorization by health-care level
I

3 908

33.9

3.9

37.8

10

II

2 256

0.26

1.82

2.1

0.9

III

622

0.004

0.072

0.076

0.12

IV

526

0.002

0.007

0.009

0.02

Categorization by income level

a

High

1 149

28.1

0.39

28.5

25

Upper middle

2 619

5.4

2.8

8.2

3.1

Lower middle

2 882

0.6

2.2

2.8

1.0

Low

662

0.0006

0.39

0.39

0.6

Global

7 312

34.1

5.8

39.9

5.5

Values are rounded; however extended precision has been preserved to illustrate differences.

52. The estimated annual total of 40 million diagnostic nuclear medicine procedures represents anincrease of 22% from the 32.7 million procedures in the UNSCEAR 2008 Report [U9]. The global
average frequency has increased from 5.1 to 5.5 procedures per 1,000 population per year.
53. Data on radionuclide therapy treatments were received from 41 countries, covering 47% of the
global population. The estimated annual number of radionuclide therapy treatments is 1.4 million, withan uncertainty of ±35%. The total was derived by combining the assessed data with the predictions of acontinuous model for countries that did not submit data to the UNSCEAR Global Survey. The
continuous model was a power-law fit to the treatment frequencies in the assessed data as a function ofphysician density. Details of the modelling are discussed in appendix A. A detailed summary is shownin table 11 with categorization by health-care level and by income level.

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63

Table 11. Global estimate of number of radionuclide treatments per annum derived from assesseddata (2009–2018) and predictions from continuous model
Category

Population(millions) a

Treatments fromassessed data
(millions) a

Treatmentsfrom modelleddata (millions) a

Total number oftreatments(millions) a

Average treatments
per 100 000
population

Categorization by health-care level
I

3 908

0.874

0.207

1.081

28

II

2 256

0.060

0.227

0.287

13

III

622

0.002

0.042

0.044

7

IV

526

0

0.020

0.020

4

Categorization by income level

a

High

1 149

0.268

0.073

0.341

30

Upper middle

2 619

0.619

0.110

0.729

28

Lower middle

2 882

0.049

0.274

0.323

11

Low

662

0

0.039

0.039

6

Global

7 312

0.936

0.496

1.432

20

Values are rounded; however extended precision has been preserved to illustrate differences.

54. The estimated annual total of 1.4 million radionuclide treatments is an increase of 63% from anannual total of 880,000 treatments estimated in the UNSCEAR 2008 Report [U9]. The global frequencyof radionuclide therapy has also increased from 14 to 20 treatments per 100,000 population per year.
Data on therapeutic administrations of radionuclides are analysed and discussed in detail in appendix D
and electronic attachment D-1.

D. Radiation therapy
55. The UNSCEAR Global Survey data were received from 44 countries, covering 66% of the total
world population. Although the number of countries providing data was low, the proportion of theworld population covered was quite high and, therefore, no additional data were incorporated in theassessment. Data on radiation therapy treatment courses do not include radionuclide therapy treatments,
which were discussed in the previous section on nuclear medicine.
56. The estimated total annual number of radiation therapy treatment courses is 6.2 million, with anuncertainty of ±25%. The total estimate was derived by combining the assessed data with thepredictions of a continuous model for countries that did not submit data to the UNSCEAR Global
Survey. The continuous model was a power-law fit to the treatment course frequencies in the assesseddata as a function of physician density. Details of the modelling are discussed in appendix A. Table 12
presents a detailed summary of the results with categorization by health-care level and by income level.
The number of treatment courses in the assessed data is also presented, along with the estimatednumber predicted by the continuous model for the remaining countries, the resulting total and theoverall average frequency of treatment courses per million population. The uncertainties stated bycountries in their survey submissions and the uncertainties of the predictions from the continuous model
were combined to derive an overall uncertainty of ±25%. Further details are given in appendix A andelectronic attachments A-1 and A-2.

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UNSCEAR 2020/2021 REPORT

Table 12. Global estimate of number of radiation therapy treatment courses per annum derived
from assessed data (2009–2018) and predictions from continuous model
Category

Population(millions) a

Treatment
courses fromassessed data
(millions) a

Treatment
courses frommodelled data
(millions) a

Total number oftreatment courses(millions) a

Average treatment
courses per million
population

Categorization by health-care level
I

3 908

4.50

1.29

5.79

1 480

II

2 256

0.225

0.154

0.379

168

III

622

0.004

0.050

0.054

85

IV

526

0

0.010

0.010

19

Categorization by income level

a

High

1 149

2.71

0.30

3.01

2 620

Upper middle

2 619

1.82

0.80

2.63

1 000

Lower middle

2 882

0.19

0.30

0.50

172

Low

662

0.0002

0.10

0.10

148

Global

7 312

4.7

1.5

6.2

853

Values are rounded; however extended precision has been preserved to illustrate differences.

57. The estimated annual total of 6.2 million treatment courses represents an increase of 22% fromthe value of 5.1 million treatment courses per annum in the previous UNSCEAR 2008 Report [U9]. The
overall rate of treatment courses has increased from 800 per million in the previous assessment to
850 per million. A comprehensive review of the published literature and further analyses of the
UNSCEAR Global Survey data on treatment frequencies, doses delivered during treatment, equipment
and staffing numbers are contained in appendix E. The UNSCEAR Global Survey data discussed inappendix E and electronic attachment E-1 indicate that, on average, brachytherapy accounts for 6.7% of
all treatment courses. On this basis, the estimated total of 6.2 million treatment courses comprises 5.8
million external beam treatment courses and 0.4 million brachytherapy treatment courses.

VI. ANALYSIS OF DOSIMETRY DATA
58. Analysis of dosimetry data was based on dose information from the UNSCEAR Global Survey.
These data included average values of physical dose quantities (such as entrance surface dose, dosearea product, dose-length product and administered activity) and assessments of typical effective dose
per examination/procedure. Physical dose quantities were converted to effective dose using theconversion factors referenced in appendices B to D. These appendices also present detailed analyses of
the country data and comparisons with dose estimates reported in the literature.
59. The effective doses presented in the following sections are based on the tissue weighting factors
from ICRP Publication 60 [I9]. This approach was adopted because the conversion factors relating
practical dose quantities to effective dose available in the literature have generally been derived using
the ICRP 60 weighting factors. There were insufficient data to derive separate estimates of effective
dose for each procedure using the tissue weighting factors from ICRP Publication 103 [I11]. In

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

65

addition, where countries submitted estimates of effective dose, it was not always clear which set oftissue weighting factors were used. As discussed in section IV, an evaluation of the overall totalcollective effective dose based on ICRP 103 weighting factors was derived by multiplying the meandoses per procedure by E-103/E-60 ratios taken from the literature [A6, A7, H5, S14, W1].

A. Diagnostic radiology
60. As described above (figure I), diagnostic radiology was considered in three subgroups:(a) conventional radiology (excluding dental), encompassing projection radiography as well asradiography and fluoroscopy, but excluding dental radiography; (b) dental radiology; and (c) computed
tomography. To ascribe doses for countries that submitted only procedure frequencies and no dose data,
and for countries where the procedure frequencies were estimated using the modelling results, the
UNSCEAR Global Survey data were used to establish typical values of effective dose for eachexamination and the mean relative frequency of each examination within the whole subgroup. These
data were combined to yield a frequency-weighted mean effective dose per subgroup examination. Thisfrequency-weighted mean effective dose per examination was used for all countries that did not provide
dose information to the current survey.
61. The typical effective doses and relative frequencies within conventional radiology (excluding
dental), dental radiology and computed tomography are shown in table 13. The frequency-weighted
effective dose for conventional radiology (excluding dental) was 0.37 mSv per examination. The mostcommon procedures were chest (two projections), limbs and joints, mammography, and pelvis and hip.
The frequency-weighted effective doses were 0.01 mSv for dental radiography and 6.4 mSv forcomputed tomography examinations. The most common computed tomography examinations werehead (brain), chest and abdomen. The uncertainties in the typical dose per examination and theuncertainties in the relative proportions were combined to derive an overall uncertainty in thefrequency-weighted effective dose. The uncertainties in the frequency-weighted effective dose per
examination were ±20% for conventional radiography, ±40% for dental radiography, and ±20% forcomputed tomography.
62. Applying a single frequency-weighted dose per procedure for all countries that did not provide
dose information assumes that procedures are performed at identical relative rates across all health-careand income levels and also that doses do not vary across these categories. These assumptions werenecessary as there were insufficient data available from the UNSCEAR Global Survey to establish
separate procedure frequencies and doses across the different health-care or income level categories.
However, the relative frequencies shown in table 13 indicate a significant contribution frommammography (13.2%, combining both clinical and screening mammography). This high frequency for
mammography reflects the fact that the survey data came mostly from HCL I countries. Survey datafrom Islamic Republic of Iran and Philippines indicated very low levels of mammography, as do data
for Kenya reported in the literature [K13]. To correct this bias, revised relative frequencies forconventional radiology (excluding dental) were calculated by replacing the relative frequencies for
mammography with the arithmetic mean of the data from Islamic Republic of Iran, Philippines and
Kenya and then re-calculating the frequencies relative to the revised total. The revised frequencies forprocedures other than mammography, therefore, increased to cover the missing proportion. The
frequency-weighted mean effective dose for conventional radiology (excluding dental) using therevised frequencies was 0.39 mSv per procedure. This revised value was ascribed to all HCL II, III and
IV countries that did not provide dose data.

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Table 13. Typical effective doses and average relative frequencies of procedures within diagnostic
radiology subcategories reported to UNSCEAR Global Survey
Examination type

Typical effective
dose (mSv) a,b

Relative frequency(%),b

CONVENTIONAL RADIOLOGY (EXCLUDING DENTAL)
Projection radiography (excluding dental)
Head (skull and facial bones)

0.08

2.3

Head (soft tissue)

0.15

0.06

Neck (cervical spine)

0.13

2.6

Neck (soft tissue)

0.51

0.05

Chest-thorax

0.08

32

Chest (thoracic spine)

0.45

1.9

Chest (shoulder girdle and ribs)

0.06

2.9

Mammography

0.22

6.0

Mammography (screening)c

0.28

7.2

Lumbar spine

1.0

6.1

Lumbo-sacral joint only

0.33

0.37

Abdomen0.61

2.9

Pelvis and hips (bone)

0.49

7.5

Pelvis (soft tissue)

1.5

0.35

Limbs and joints

0.02

21

Whole spine (trunk)

1.5

0.20

Skeletal (head and trunk)

0.5

0.29

Othersd

0.22

2.9

Gastrointestinal tract (barium studies)

3.4

0.59

Gastrointestinal tract (defecography)

8.8

0.04

Biliary tract (cholangiography)

8.5

0.02

Biliary tract (endoscopic retrograde cholangiopancreatography)

4.9

0.06

Biliary tract (cholecystography)

1.4

0.01

Urogenital tract (Intravenous urography)

2.4

0.23

Urogenital tract (kidney, bladder and urethra)

1.6

0.12

Myelography

5.5

0.01

Arthrography

2.1

0.09

Cerebral angiography

6.9

0.03

Cardiac angiography

7.0

0.78

Thoracic angiography

4.8

0.08

c

Radiography and fluoroscopy

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Examination type

Typical effective
dose (mSv) a,b

Relative frequency(%),b

Abdominal angiography

8.0

0.03

Pelvic angiography

7.5

0.02

Peripheral angiography

3.2

0.09

Lymphangiography

1.00.0002Othersd

4.8

1.1

Weighted dose per examination for conventional radiology(excluding dental)

0.37

67

Dental radiology
Dental intraoral

0.006

74

Dental panoramic

0.024

26

Weighted dose per examination for dental radiology

0.01

Computed tomography (CT)abCT-head (skull and facial bones)

1.5

13.6

CT-head (soft tissue and brain)

1.9

16.4

CT-neck (cervical spine)

3.1

2.9

CT-neck (soft tissue)

2.8

1.2

CT-chest (thoracic spine)

8.0

1.4

CT-chest (thorax)

6.4

15.7

CT-abdomen (lumbar spine)

9.4

4.2

CT-abdomen (abdomen)

11

15.4

CT-abdomen (liver, pancreas, kidneys)

10

3.2

CT-pelvis (pelvic bones)

8.8

2.4

CT-pelvis (pelvic soft tissue and vascular)

11

2.8

CT-pelvis (pelvimetry)

5.0

0.05

CT-full spine (neck, chest, abdomen)

14

1.4

CT-trunk (chest, abdomen, pelvis)

17

3.9

CT-limbs

2.1

2.4

CT-dental

0.7

0.3

Cone beam CT-dental

0.13

1.0

Cone beam CT-others

0.06

0.1

Othersd

6.4

11.5

Weighted dose per examination for computed tomography

6.4

For the effective dose determination, ICRP 60 [I9] tissue weighting factors were applied.

Values are rounded; however extended precision has been preserved to illustrate differences.
Effective doses for mammography reported to UNSCEAR Global Survey were assumed to be based on ICRP 103 [I11] tissue
weighting factors and were divided by 2.4 to adjust them to ICRP 60 [I9] for consistency with doses for all other procedures.
dProcedures categorized as “Others” were assigned a dose equal to the frequency-weighted average dose for all otherprocedures within the category.
c

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UNSCEAR 2020/2021 REPORT

63. The total annual number of examinations worldwide is assessed as 2.6 billion for conventional
radiography, 1.1 billion for dental radiography and 400 million for computed tomography (table 4). The
global collective dose for conventional radiology (excluding dental), dental radiology and computed
tomography is 955,000 man Sv, 9,700 man Sv, and 2,556,000 man Sv, respectively. The distribution ofcollective dose between health-care and income levels, along with the contribution to the per caput
effective dose, is presented in table 14. Combining the uncertainties in the number of procedures withthe uncertainties in the dose per procedure, as described in appendix A, leads to an overall uncertainty
in the collective dose of ±45% for conventional radiology (excluding dental), ±70% for dental
radiography, and ±45% for computed tomography.
64. A comprehensive review of the published literature, and further analyses of the UNSCEAR
Global Survey data on procedure frequencies, doses per procedure, equipment and staff in diagnostic
radiology are discussed in appendix B.
Table 14. Comparison of estimated annual collective dose and annual per caput effective dose
between health-care and income levels for conventional radiology (excluding dental), dental
radiology and computed tomography
The estimates are based on survey data and the continuous mathematical model (physician density)
Category

Conventional radiology(excluding dental)
Collective dose
(1 000 man Sv) a

Effective dose
per caput(mSv) aDental radiology
Collective dose
(1 000 man Sv) a

Effective dose
per caput(mSv) aComputed tomography
Collective dose
(1 000 man Sv) a

Effective dose
per caput(mSv) aCategorization by health-care level
I

651

0.17

8.5

0.0022

2 050

0.52

II

254

0.11

1.1

0.0005

449

0.20

III

37

0.059

0.07

0.0001

45

0.073

IV

13

0.026

0.01

0.0000212

0.024

Categorization by income level

a

High

355

0.31

5.0

0.0044

1 178

1.02

Upper middle

265

0.10

2.9

0.0011812

0.31

Lower middle

305

0.11

1.6

0.0005

516

0.18

Low

30

0.046

0.15

0.000250

0.075

Global

955

0.13

9.7

0.0013

2 556

0.35

Values are rounded; however extended precision has been preserved to illustrate differences.

B. Interventional radiology
65. A frequency-weighted effective dose per interventional radiology procedure was established forthe purpose of ascribing doses for countries that submitted only procedure frequencies and no dosedata, and for countries where the procedure frequencies were estimated using the continuous model.
The submitted UNSCEAR Global Survey data were used to establish typical values of effective dosefor each procedure and the mean relative frequency of the procedure within all interventional radiology

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

69

procedures (table 15). This frequency-weighted effective dose per procedure was used for all countries
that did not provide dose information to the UNSCEAR Global Survey. The frequency-weighted
effective dose derived for interventional radiology was 14.9 mSv per procedure. Combining theuncertainties in the typical doses for procedures and the uncertainty in the relative proportions gives anoverall uncertainty in the frequency-weighted effective dose per procedure of ±50%.
Table 15. Typical effective doses and average relative frequencies of procedures for interventional
radiology
PTCA: Percutaneous transluminal coronary angioplasty; TIPS: Transjugular intrahepatic portosystemic shunt
Typical effective dose(mSv) aRelative frequency(%)

Head (cerebral intervention)

12.6

1.0

PTCA

20.6

37.6

Chest (pacemaker)

1.4

4.8

Thoracic intervention (other)

2.8

8.1

Abdomen (biliary and urinary intervention)

7.2

3.3

Abdomen (TIPS)

27.8

0.1

Abdominal interventions (other)

32.0

1.8

Pelvic interventions

7.0

1.0

Limb interventions

13.6

3.8

Other interventional procedures

13.9

38.5

Weighted dose per procedure

14.9

Examination typea

For the effective dose determination, ICRP 60 [I9] tissue weighting factors were applied.

66. The global number of interventional radiology procedures is assessed at 24 million and the global
collective effective dose is assessed at 334,000 man Sv. The distribution of collective dose between
health-care and income levels, along with the contribution to the per caput dose, is shown in table 16.
Combining the uncertainty in the number of procedures with the uncertainty in the dose per procedure,as described in appendix A, leads to an overall uncertainty in the collective effective dose frominterventional radiology of ±90%. A comprehensive review of the literature and a detailed analysis ofdata on procedure frequencies, doses per procedure, equipment and staff are discussed in appendix C.

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Table 16. Comparison of estimated annual collective dose and annual per caput effective dose
between health-care and income levels for interventional radiology
The estimates are based on survey data and the continuous mathematical model (physician density)
Category

Collective dose (1 000 man Sv) a

Per caput effective dose (mSv) a

Categorization by health-care level
I

269

0.069

II

59

0.026

III

4.7

0.008

IV

1.3

0.002

Categorization by income level

a

High

193

0.168

Upper middle

69

0.026

Lower middle

65

0.023

Low

7

0.010

Global334

0.046

Values are rounded; however extended precision has been preserved to illustrate differences.

C. Nuclear medicine
67. In diagnostic nuclear medicine, a more complicated process of ascribing doses for countries that
submitted only procedure frequencies and no dose data, and for countries where the procedure
frequencies were estimated using the continuous model, was chosen. The UNSCEAR Global Survey
data were used to establish typical values of effective dose for each procedure and the average relative
frequency of the procedure within the categories of gamma camera and SPECT procedures, and PET
procedures, respectively. The relative frequencies with which different radiopharmaceuticals anddifferent radionuclides were used for a given procedure were included in the assessment of effective
dose for that procedure. The proportion of procedures including an accompanying attenuation
correction or localization computed tomography scan, and the fraction of PET procedures within theoverall total procedures (table 17) were included in the calculation of the overall frequency-weighted
effective dose per procedure. The frequency-weighted effective dose derived for diagnostic nuclear
medicine was 6.8 mSv per procedure. This weighted effective dose per procedure was used for all
countries that did not provide dose information to the UNSCEAR Global Survey. For countries with noreported PET equipment, only the weighted dose for gamma camera and SPECT procedures (5.1 mSv
per procedure) was used in the assessment. The uncertainties in the typical doses for nuclear medicine
procedures and the uncertainty in the relative frequencies were combined to derive an overall
uncertainty in the weighted effective dose. The estimated overall uncertainty in the weighted effective
dose per procedure is ±20%.

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71

Table 17. Typical effective doses and average relative frequencies of nuclear medicine procedures
CT: Computed tomography; PET: Positron emission tomography; SPECT: Single photon emission computed
tomography
ProcedureRadiopharmaceutical component a
Isotope

Typical effective
dose (mSv)

Relativefrequency (%)

CT component a
Typical effective
dose (mSv)

Fraction of
CT (%)

0.3

54

GAMMA CAMERA AND SPECT PROCEDURES
Nervous system

99m

Nervous system

123

Tc

6.6

1.8

I

9.2

1.9

Skeletal

99m

Tc

3.6

28.4

3.0

34

Cardiovascular

99m

Tc

6.8

23.7

1.0

55

Cardiovascular

201

Tl

14.4

3.4

Pulmonary

99m

Tc

2.3

6.3

1.9

30

Endocrine

99m

Tc

3.0

12.8

Endocrine

123

I

24.5

1.6

1.4

24

3.2

6

Gastrointestinal

99m

Tc

2.9

2.3

Genitourinary

99m

Tc

1.1

8.7

Oncology

All

6.8

3.6

2.7

54

Infection, inflammation

99m

Tc

6.8

2.0

2.5

81

Lymphatics

99m

Tc

0.08

3.5

Weighted dose per procedure (mSv)

4.9

Fraction of SPECT systems with CT

0.6
32.2

Weighted CT component

0.2

Weighted dose per gamma camera and SPECT

5.1

PET PROCEDURES
Oncology

18

Oncology

68

F

15.9

90.7

Ga

12.4

1.3

Cardiovascular18

Cardiovascular

15

F

15.4

1.7

O

1.6

0.3

Skeletal

18

F

16.9

1.3

Nervous system

18

F

5.4

2.6

Infection, inflammation

18

F

16.8

0.5

Weighted dose per PET procedure (mSv)

Doses include CT component

15.3

Fraction of PET in all nuclear medicine procedures

17

Combined weighted dose for nuclear medicine including PETa

All procedures assumed toinclude CT

For the effective dose determination, ICRP 60 [I9] tissue weighting factors were applied.

6.8

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68. The total number of procedures worldwide in diagnostic nuclear medicine (including PET) isassessed as 40 million. The global collective effective dose is assessed at 297,000 man Sv. The
distribution of collective dose between health-care and income levels, along with the contribution to theper caput effective dose, is shown in table 18. Combining the uncertainty in the number of procedureswith the uncertainty in the dose per procedure, as described in appendix A, leads to an overall
uncertainty in the collective effective dose from diagnostic nuclear medicine of ±75%. A
comprehensive review of the literature and further analyses of the survey data on procedure
frequencies, doses per procedure, equipment and staff in nuclear medicine are discussed in appendix D.
Table 18. Comparison of estimated annual collective dose and annual per caput effective dose
between health-care and income levels for diagnostic nuclear medicine
The estimates are based on survey data and the continuous mathematical model (physician density)
Category

Collective effective dose
(1 000 man Sv) a

Effective dose per caput(mSv) aCategorization by health-care level
I

285

0.073

II

11.1

0.005

III

0.44

0.0007IV

0.05

0.0001Categorization by income level

a

High

235

0.20

Upper middle

46

0.018

Lower middle

14

0.005

Low

2

0.003

Global297

0.041

Values are rounded; however extended precision has been preserved to illustrate differences.

69. The uncertainty in the global estimate of medical exposure arises from a number of sources. Somecountries conducted a survey of a limited number of nuclear medicine practices and then extrapolated
the data to the whole country. This can lead to an over- or underestimation of the true number ofprocedures, depending on how representative the sample sites are of the whole country. Further, there
are often a number of different radiopharmaceuticals available for any one procedure and the particular
one used may vary from site to site and from patient to patient, depending on their clinical history.
Additionally, while computed tomography is now used in almost all PET procedures, this is not thecase with SPECT. Although the number of SPECT/CT installations has increased markedly in the past
decade, the computed tomography component is usually used in less than 55% of cases. It is common
practice to perform the SPECT study first, and then perform the computed tomography only if the study
is abnormal and the anatomical localization of the abnormality cannot be clearly identified from the
SPECT images. This level of detail is often not available in national surveys but needs to be considered
for future surveys.

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73

VII. DISTRIBUTIONS BY AGE AND SEX
70. The UNSCEAR Global Survey provided detailed data on the distribution of procedures by age
and sex for a number of countries. Data was provided by ten countries for projection radiography(without contrast), and for radiography and fluoroscopy (with contrast). Data for computed tomography
was provided by eleven countries, for interventional radiology by eight countries, for nuclear medicine
by 13 countries, and for radiation therapy by nine countries. With the exception of Thailand, all data on
the age and sex distribution of procedures came from HCL I countries. Detailed discussions of the age
and sex distributions are presented in appendices B to E .
71. The distributions of projection radiography (without contrast), radiography and fluoroscopy (withcontrast), computed tomography, interventional radiology and nuclear medicine procedures by patientage are presented in figure III. Computed tomography, radiography and fluoroscopy (with contrast),
interventional radiology and nuclear medicine show very similar age profiles, with the bulk ofprocedures occurring in patients aged 55 years and older. Projection radiography (without contrast)shows a markedly flatter profile, with many procedures performed on children and young adults. The
distribution for computed tomography also shows elevated rates between ages 15 and 44 in comparison
with radiography and fluoroscopy, interventional radiology and nuclear medicine.
Figure III. Comparison of age distributions for examinations/procedures by modality categories,
averaged across countries reported data to UNSCEAR Global Survey

72. The proportions of examinations/procedures by patient sex are presented in figure IV. The malefemale ratio is close to even for computed tomography and nuclear medicine procedures. Fluoroscopic
examinations show a slight preponderance of males, while interventional procedures show a strong
tendency to males with a ratio close to 2:1. The preponderance to males in interventional radiology isseen for many procedure types but particularly for percutaneous coronary angioplasty (PTCA). By
contrast, projection radiography is weighted towards females, mainly due to the contribution frommammography examinations. Only a few countries were able to provide data on age and sex
distributions of examinations/procedures. It is desirable to have such data also from lower middleincome and low-income countries where the age structure of the population, clinical presentations,equipment, staffing and practice may differ from the results presented in this annex.

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UNSCEAR 2020/2021 REPORT

Figure IV. Distributions of patient sex received radiological examinations by modality categories,
averaged across countries reported data to UNSCEAR Global Survey

VIII. TRENDS IN MEDICAL EXPOSURE
73. The results of this current evaluation are compared with matching data from the UNSCEAR 2008
Report [U9] in table 19. Comparisons for selected procedures within conventional radiology (excluding
dental) are also shown to highlight major changes.
74. The estimated number of procedures in conventional radiology (excluding dental) is lower in thepresent assessment by about 10%, and there is a large reduction, approximately 60%, in the assessedcollective effective dose. There are some differences in methodology that contribute to the lower
number of estimated procedures. The previous assessment included counts of individual radiographic
projections in some cases, whereas the present assessment attempts to estimate the number ofprocedures, some of which may include multiple projections. The present assessment also uses
modelling to ascribe procedures to countries that did not submit data, instead of applying populationweighted averages from the current survey to all countries within each health-care level.
75. As discussed in more detail in appendix B typical effective doses for radiography procedures havegenerally decreased during the past decade, although there continues to be wide variation in reported
values. Significant reductions in procedure frequencies are seen for studies of the gastrointestinal
system using fluoroscopy and contrast. These procedures contributed 640,000 man Sv to the collective
dose in the previous assessment. In the present assessment, the number of procedures and the collective
dose have fallen by approximately 90%. The frequencies of radiographic and fluoroscopic
examinations of the biliary and urinary systems have also fallen considerably and their contribution to
the collective dose has decreased. A recent evaluation of medical exposure in the United States [N2]also found notable reductions in fluoroscopic gastrointestinal examinations, which in that case wereascribed to a shift to fibre-optic endoscopy and colonography.

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75

Table 19. Comparison of annual number of examinations/procedures and annual collective dosefrom medical exposure with UNSCEAR 2008 Report [U9]Modality categorya

UNSCEAR 2008 Report [U9]Current evaluation

Number of
examinations /procedures(millions) a

Collective dose
(1 000 man Sv) a

Number of
examinations/procedures(millions) a

Collective dose
(1 000 man Sv) a

Conventional radiology(excluding dental)

2 900b

2 350

2 626

955

Chest (thorax)

930

93

955

97

Chest photofluorography

440

340

64

c

19c

Mammography (clinical)

50

19

120

27

Mammography (screening)

80

22

110

29

Gastrointestinal

135

640

18

65

Biliary system

40

76

2

11

Urography

45

120

8.6

19

Others

240

390

120

140

Dental

480

11

1 100

10

Computed tomography

220

1 540

403

2 556

Interventional radiology

3.6

d

41

23.6

334

Diagnostic nuclear medicine

33

202

39.9

297

Radionuclide therapy

0.88

1.4

Radiation therapye

5.1

6.2

Values are rounded; however extended precision has been preserved to illustrate differences.

b

UNSCEAR 2008 Report [U9] counted individual projections rather than whole examinations in some cases.

c

Data reported by the Russian Federation, however, this category was not included in the UNSCEAR Global Survey.

dData for interventional radiology were not reported separately in UNSCEAR 2008 Report [U9]. The value reported here isaccording to the definition of interventional radiology used in this annex.
eRadiation therapy was counted as courses of treatment, not individual treatment fractions.

76. Chest photofluorography contributed approximately 340,000 man Sv to the collective dose in theprevious UNSCEAR 2008 Report [U9]. There is no directly equivalent category for this procedure in
the present assessment, however specific data were reported by the Russian Federation. In other cases,
these procedures may have been reported under the chest category. A comparison of the chest (thorax)
category is included in table 19. The number of chest procedures and the assessed collective dose has
increased, but only marginally. As discussed by Balonov et al. [B6], the use of fluorography has
declined in the Russian Federation (see also appendix B), although it was reported to account for 44%of the total collective effective dose in Ukraine during the period 2009–2012 [S22].
77. The current evaluation shows a significant increase in the use of mammography. As discussed in
section VI.A, a revised set of relative frequencies with a very low mammography component was usedin ascribing procedures and doses to countries in HCL II, III and IV that did not submit data to the
UNSCEAR Global Survey. The total for mammography examinations reported in table 19 are thus
largely due to procedures in HCL I countries, both those included in survey submissions and thoseascribed for countries that did not submit data. As discussed in appendix B, the survey data showed a

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consistently large increase in the frequency of mammography examinations compared to the previous
UNSCEAR 2008 Report [U9].
78. In dental radiology, the assessed number of procedures has doubled although the overallcollective dose is similar. This increase may be due to an increased level of reporting for the
UNSCEAR Global Survey. It should be noted that dental cone beam computed tomography (CBCT)
has been counted and analysed within the computed tomography category, as presented in appendix B.
79. In computed tomography, the number of procedures and the collective dose have risen markedly.
The number of procedures has increased by about 80% and the collective dose has increased by around70%. As discussed in appendix B, an increase is observed for most countries submitting data to the
UNSCEAR Global Survey; however, the procedure frequencies per 1,000 population assessed for HCL
II, III and IV countries in this evaluation have increased by factors of 4 (7 to 31), 3 (3 to 11) and 1.2 (3to 3.7), respectively. While there is evidence of some reduction in the average dose per procedure, useof computed tomography continues to grow.
80. In interventional radiology, the number of procedures has increased by a factor of 6 and thecollective dose has increased by a factor of 8 compared to the previous assessment [U9]. This reflects
both an increasing deployment of interventional radiology and an expansion in the range of procedure
types with higher doses per procedure, on average. The large apparent change is also due in part to gaps
in reporting; the previous assessment did not include cerebral and vascular procedures on the basis thatthese were largely diagnostic and not therapeutic. Although interventional procedures are less frequent
than radiography or computed tomography examinations, the effective dose per procedure is relatively
high. As a result, interventional procedures make an important contribution to the total collective dose.
Coronary angioplasty remains the most frequent interventional procedure.
81. In nuclear medicine, the assessed number of procedures has increased by 20% and the collective
dose has increased by 50%, indicating a growth in higher dose procedures. The greatest change in thepast decade has been the steady increase in the number of PET procedures, which now represent 17%of all nuclear medicine procedures. With a typical effective dose of 15 mSv per procedure (including
both radiopharmaceutical and computed tomography dose), increasing use of PET will lead to a rise in
the average dose per procedure. The use of PET is likely to increase further with the initiation of new
radiopharmaceuticals currently under clinical development and the growing role of PET in cancer care.
Throughout the world, PET/CT systems have now largely replaced stand-alone PET systems.
SPECT/CT systems have been available since about 2005, but information in the literature on theirdistribution is very limited. The previous rapid rise in the number of cardiac studies, particularly in the
United States, appears to have moderated and reversed slightly.
82. Table 20 summarizes the trends in medical exposure for diagnosis and intervention since 1988.
The values include the total annual number of examinations and collective effective doses fromdiagnostic and dental radiology, nuclear medicine and interventional radiology. However, no data for
frequencies for dental radiology were given in the UNSCEAR 1993 Report [U5], which explains theslight decrease (figure V). The annual total number of examinations has increased from 1.7 billion in1988 to 4.2 billion in the current evaluation. This increase is due partly to the increase in the global
population, but the frequency of examination has also increased from 355 to 574 procedures per 1,000
population (figure VI). However, compared with the previous UNSCEAR evaluation [U9], the increaseis minor. The estimated annual collective effective dose to the world population from medical
radiological examinations has increased from 1,890,000 man Sv in 1988 to 4,150,000 man Sv in thecurrent evaluation (figure VII). The annual per caput effective dose increased from 0.37 mSv in 1988 to
0.65 mSv in 2008 and has fallen slightly since, to 0.57 mSv (figure VIII).

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Table 20. Comparison of UNSCEAR global medical exposure evaluations
Evaluation

Annual number of
examinations(millions) a

Annual frequency of
examinations per
1 000 population a

Annual collective
effective dose
(1 000 man Sv) a,b

Annual effective
dose per caput(mSv) a, b

UNSCEAR 1988
Report [U4]

1 740

355

1 890

0.37

UNSCEAR 1993
Report [U5]

1 620

305

1 780

0.33

UNSCEAR 2000
Report [U6]

2 460

426

2 460

0.43

UNSCEAR 2008
Report [U9]

3 660

561

4 210

0.65

Current
evaluation

4 190

574

4 150b0.57

aValues are rounded.

b

For the effective dose determination, ICRP 60 [I9] tissue weighting factors were applied.

83. Overall, the current evaluation shows only a slight change from the UNSCEAR 2008 Report [U9]and a slight reduction in the effective dose per caput. This contrasts with the previous two UNSCEAR
reports [U6, U9], which showed notable increases, not only in the total number of examinations but
also in the frequencies of examinations per 1,000 population and the annual effective dose per caput. As
discussed above, this evaluation shows the influence of technological changes and changes in medical
practice as previously more common procedures were supplanted by different techniques or phased out
entirely. The use of computed tomography has continued to grow and the contribution frominterventional radiology has increased rapidly. It appears likely that these two trends will continue and,thus, the effective dose per caput may be expected to rise again in the future as access to thesetechniques using ionizing radiation spreads to lower middle- and low-income countries.
84. Figure IX shows that the frequency of radionuclide therapy has increased by 40% since the
UNSCEAR 2008 Report [U9], continuing a trend of increasing use seen in previous UNSCEAR
reports. In the past decade, a number of new therapies have been introduced clinically and are now
available in many countries. These include 90Y-microspheres for the treatment of liver tumours, 177Luoctreotide for neuroendocrine tumours and 177Lu labelled onto prostate-specific membrane antigen(177Lu-PSMA) for prostate cancer. Statistics on the use of these newer therapies are often limited so thefrequencies estimated in this evaluation are likely to be an underestimate. Considerable research isunder way into “theranostics”, in which the same pharmaceutical is used for both diagnosis andtreatment. This is likely to lead to the establishment of these new procedures in routine clinical practicein many countries in coming years.

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UNSCEAR 2020/2021 REPORT

Figure V. Trend in global annual number of medical radiological examinations/procedures

Figure VI. Trend in global annual frequency per 1,000 population of medical radiologicalexaminations

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Figure VII. Trend in global annual collective effective dose from medical radiological examinations

Figure VIII. Trend in global annual effective dose per caput from medical radiological examinations

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UNSCEAR 2020/2021 REPORT

Figure IX. Trend in global annual frequency of radionuclide therapy treatments

Figure X. Trend in global annual frequency of courses of radiation therapy treatment (excluding
radionuclide therapy)

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81

85. The annual number of courses of radiation therapy treatment (excluding radionuclide therapy) is
estimated to have increased from 5.1 to 6.2 million since the UNSCEAR 2008 Report [U9]. However,the long-term trend in the frequency of radiation therapy treatment courses shows little change(figure X). There is a trend towards greater sparing of normal tissues and improved conformity with thetarget volume. This trend is made possible by the increase in technological sophistication of treatment
delivery: specifically, the use of image guidance and of delivery techniques such as intensity-modulated
radiation therapy (IMRT), volumetric modulated arc therapy (VMAT), particle beams and stereotactic
techniques [K7].
86. The trends in improved geometric targeting have been accompanied by a trend towards higher
tumour dose, or higher dose per fraction combined with a smaller number of fractions. These changes
recognize the reduced doses delivered to normal tissues enabling an escalation of tumour dose, thusachieving greater tumour control without an increase in normal tissue toxicity.

IX. IMPLICATION FOR FUTURE ANALYSES
87. The compilation of a global assessment of medical exposure is a complex task. Data must be
sourced from a wide array of locations, checked for consistency, and integrated into an overallsummary. The recommendations below are intended to facilitate the process; allowing for improved
data collection, speed and robustness of future assessments by the Committee.
88. As national surveys of medical exposure require adequate planning, with significant time andresources, the Committee recommends the use of its UNSCEAR Global Survey questionnaires (especiallythe essential data sets) to collect such information on a regular basis. Also, the Committee intends to
update its assessments more often through a focus on essential data, which includes annual total numbersof examinations/procedures within each broad type of radiological discipline: conventional radiology,
dental radiology, computed tomography, interventional radiology, nuclear medicine and radiation therapy.
89. National surveys of medical exposure should include, whenever possible, information on age andsex distribution of patients by the major types of medical examinations. In particular, estimations ofcollective dose to paediatric patients are of special interest. The Committee recommends thatfrequencies of radiological examinations be reported per 1,000 population. The population data and thetypical doses for examinations used to derive the collective dose should be clearly stated, as should theperiod to which the data refer. This will facilitate the compilation of global summaries and comparative
analysis of data between countries. For projection radiology, in particular for frequency data, it should
always be made clear whether dental examinations are included or not.
90. The collection and collation of national data on medical exposure is not a simple process;however, the publication of more data on collective doses and trends in medical exposure from lower
middle-income and low-income countries is desirable, as imaging patterns and technology may changequite rapidly in these countries.
91. Regular assessment of typical effective doses for medical examinations is important in order totrack any optimization of technique due to factors such as the uptake of new technologies, improved
training for operators and the availability of expert advice. Changes in practice and levels of exposure
likely occur in a gradual fashion over time. Regular published assessments of typical doses would
facilitate the tracing of trends.

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92. Initiatives for future evaluations by the Committee should focus on motivating submission, ofeven partial data sets of key information (essential data), from countries not represented in thisevaluation. Further, action should target countries with large populations (and so potentially significant
contributors to global practice) and also those with developing levels of health care. It might be useful
to focus data collection efforts on examinations and procedures that contribute most to the populationdose, such as the TOP 20 methodology developed the EC DDM 1 project [E3].
93. The success of the EC DDM 2 project [E5] in facilitating data collection for the assessment of
population dose in Europe could form the basis for similar regionally-organized initiatives, also
involving the training of national contact persons in population dose assessment and organized datacollection. These could help promote national surveys elsewhere, such as in Africa, Asia and Latin
America, and so increase participation in future UNSCEAR Global Surveys.
94. There is generally a huge variation in the typical effective dose per radiological examination usedin different countries, which subsequently affects the variations in estimated collective doses. Part ofthis variation is due to the use of different methods of estimation, including different conversion factors(effective dose per dosimetric quantity). The applicability, accuracy and consistency of the various
approaches should be addressed for future studies. The conversion factors used to estimate effective
dose should be reported in the surveys.
95. The impacts of technological changes in computed tomography—increasing numbers ofsimultaneously acquired slices, the introduction and use of dose saving features, and evolving
diagnostic applications—are quite complex. There are both decreasing and increasing trends in themean effective dose per examination, which have significant implications for the overall estimatedcollective effective dose from medical exposure.
96. Revised categories for interventional radiology procedures should be considered for futurecollection and reporting of medical exposure data. Cardiac procedures are studied more than any otherinterventional radiology procedure. This is justified due to their high frequency and radiation dose;
however, a focus on these procedures may mean that interventional radiology procedures performed
outside traditional radiology and cardiology departments are omitted from reporting due to the lack ofan appropriate category, e.g., vascular procedures or vertebroplasties. Moreover, any system ofcategorization and analysis needs to allow for the fact that the distinction between diagnosis andintervention is becoming increasingly blurred. Procedures frequently begin as diagnostic in intent but
will progress to intervention as dictated by the needs of the particular case (for instance, a diagnostic
coronary angiography procedure that is followed by a PTCA). The combination of many examinations
in a single group makes it difficult to assess exposure and to interpret trends (e.g., PTCA and cardiac
ablation may be reported under a single “cardiac” category although patient exposure differs
substantially). Careful evaluation of categories to be included in future surveys will be needed.
97. Continuing advances in imaging technology and interventional techniques allow the treatment of
more complex medical conditions; however, these increasingly complex procedures may involve higher
patient exposure and a greater likelihood of exceeding thresholds for tissue reactions. While data on thefrequency of tissue reactions have not typically been within the scope of assessments of medical exposure,
future surveys could include the possibility of reporting skin doses in interventional radiology procedures.
98. National surveys of nuclear medicine procedures need to include the dose from the computed
tomography component of PET/CT and SPECT/CT examinations. When including the computed
tomography component for SPECT, it is important to recognize that (a) not all SPECT examinations
will require SPECT/CT; (b) some examinations will require more than one SPECT/CT; and (c) for
certain examinations, particularly skeletal imaging, the SPECT/CT could cover any part of the body. In

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83

some cases, full diagnostic computed tomography will be performed, and future surveys will need toconsider whether to count and analyse such procedures as a component of nuclear medicine studies orto include them with regular diagnostic computed tomography examinations.
99. Future evaluation of nuclear medicine will need to expand the recorded frequency data to allow
for a number of possible radiopharmaceuticals for one clinical procedure to be considered in order tomore accurately determine the collective dose. This particularly applies to gastroenterology, renal, brain
and oncology procedures where several different radiopharmaceuticals may be used, depending on theclinical indication for the study.
100. Only one publication [K10] reported on the frequencies of therapeutic nuclear medicine
procedures. As this is an area of increasing application, statistics on the number of patients being
treated with the growing range of radiopharmaceuticals is needed.
101. Future evaluations of radiation therapy practice will need to clarify the data requested, including
the number of courses of treatment, the conditions for which patients are treated (including benign
conditions), as well as the most common treatment modalities, doses and numbers of treatment
fractions delivered.
102. The global assessment of medical exposure has focused on the frequencies of examinations/procedures and estimates of dose per procedure/examination. This approach assesses the overallcollective exposure but does not provide information on the distribution of doses from medical
exposure to individual patients. Only a few peer reviewed papers discuss cumulative doses due tomultiple examinations performed on the same patient, although the issue of the number of patients
receiving cumulative doses greater than 100 mSv has been raised recently [B31, R6, R7]. Collection ofdata on cumulative doses to patients, similar to the collection of data on occupational exposure, is
important for improved analyses of trends and for the implications for patient management.
103. The impact of the use of either ICRP 60 [I9] or ICRP 103 [I11] tissue weighting factors should becomprehensively analysed and future global assessments should be directed towards using the ICRP 103
tissue weighting factors. An analysis is needed to study any changes introduced into global medical
exposure estimates due to this change compared with other factors. In the current evaluation, there was aminor impact for conventional radiology (excluding dental), computed tomography and interventional
radiology (+0.9%, −1.5% and −0.5%, respectively), a 15% reduction for diagnostic nuclear medicine, andan 88% increase for dental radiology. However, the overall impact on the collective effective dose was,with a reduction of 1.6%, rather small.

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UNSCEAR 2020/2021 REPORTX. SUMMARY AND CONCLUSIONS
104. Medical exposure remains by far the largest human-made source of exposure of the general
population to ionizing radiation. From the present assessment, it was concluded that about 4.2 billion
medical radiological examinations are performed annually. The total annual collective effective dose to
the world population of 7.3 billion people is estimated to be 4.2 million man Sv. The uncertainty in theestimate of the number of examinations is assessed as ±30% and the uncertainty in the collective
effective dose is also assessed as ±30%. Further, the Committee estimated 6.2 million courses ofradiation therapy treatment performed each year, about 5.8 million by external beams and 0.4 million
by brachytherapy. In addition, 1.4 million radionuclide therapy treatments are estimated to be
performed annually.
105. Conventional radiology (excluding dental) accounts for about 63% of all medical radiologicalexaminations and 23% of the collective dose. Dental radiology accounts for about 26% of theexaminations but only 0.2% of the overall collective dose. Computed tomography makes the largest
contribution (62.6%) to the overall collective dose but accounts for only about 10% of all examinations.
Interventional radiology accounts for only 0.6% of medical radiological examinations but contributes
8% of the overall collective dose. Diagnostic nuclear medicine procedures account for 1% of all
medical radiological examinations and 7.2% of the overall collective dose.
106. The estimated annual effective dose per caput from medical radiological examinations has fallenslightly compared to the Committee’s previous assessment in 2008 [U9] (from 0.65 to 0.57 mSv). The
difference is, however, within the bounds of the estimated uncertainty. This trend stands in contrast to
the trends observed in the previous two UNSCEAR reports [U6, U9], which showed notable increases.
107. The use of computed tomography has continued to expand and has replaced some of the older
radiography and fluoroscopy examinations. However, there has been a major reported reduction inradiography and fluoroscopy examinations of the gastrointestinal tract, and also reduction influoroscopy examinations of the biliary and urinary systems and of the chest region. The contribution ofinterventional radiology has increased dramatically and now accounts for 8% of the collective dose(compared to 2% in the previous assessment), despite only accounting for 0.6% of the total number of
examinations. Nuclear medicine continues to account for around 1% of all examinations and its
contribution to the collective dose has risen from 5% to about 7%. The number of radionuclide therapy
treatments is estimated to have increased by 60% since the UNSCEAR 2008 Report [U9], while thenumber of courses of radiation therapy has increased by 22%.
108. The age distributions of patients undergoing computed tomography, interventional radiology andnuclear medicine examinations are quite similar, with the bulk of examinations occurring in patients
aged 55 years and older. Conventional projection radiography shows a markedly flatter profile, withmany examinations performed on children and young adults. The distribution of examinations between
the sexes is generally even, although interventional radiology procedures, especially in cardiology,
show a higher proportion of males. Projection radiography is weighted towards females, mainly due tothe contribution from mammography examinations.
109. The use of radiation for diagnosis and therapy continues to be strongly weighted to high-income
and upper middle-income countries. These countries account for around 70% of all medical radiologicalexaminations and 75% of the overall collective dose. This disparity is even more marked in nuclear
medicine where high-income and upper middle-income countries account for over 90% of theANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

85

procedures and more than 95% of the collective dose. Access to radiation therapy is similarly
concentrated, with around 95% of all treatment courses occurring in high-income and upper middleincome countries.
110. The results of this global assessment of medical exposure were derived, for the first time, from acontinuous model using data from the UNSCEAR Global Survey to generate predictions for countries
that did not provide data, rather than by extrapolation of averaged data within health-care level
categories. It is important to recognize that both the modelling and extrapolation approaches require
representative data to reflect the broad patterns of use and exposure to derive a robust overall global
assessment. Thus, the Committee wishes to highlight the importance of regular collection andpublication of medical exposure data and seeks support to initiate data collection programmes for lower
middle-income and low-income countries for its future evaluations.
111. Systematic collection, analysis and interpretation of relevant health data is essential for designing,
implementing and evaluating health policies and actions. In particular, data collection within eachcountry and inclusion of such data in global surveys such as the UNSCEAR assessments offers several
benefits to participating countries. By knowing about health parameters such as frequency of medical
examinations and procedures involving the use of ionizing radiation, as well as associated doses perprocedure, the participating countries can inform the development of policies and strategies for the
optimization of health-care delivery and improve practice. In addition, disparities in health-caredelivery involving use of ionizing radiation in regions of a country can be identified and evaluatedalongside other relevant health indicators. Population doses due to medical exposure can be determined
and tracked in the context of temporal trends in regions and around the globe. Furthermore, results fromsurveys such as the UNSCEAR Global Survey can serve as reference material for researchers, students
and government advisory bodies.

86

UNSCEAR 2020/2021 REPORTACKNOWLEDGEMENTS
The Committee acknowledges with gratitude the work of the members of the Expert Group involved in
preparing this annex and especially P. Thomas and A. Wallace (Australia) who chaired the Expert Groupin the periods 2019–2020 and 2016–2019, respectively. The Committee, in particular, thanks E. Nekolla(Germany), H. Järvinen (Finland), R. Smart (Australia), E. Samara (Switzerland) and G. Ibbott (UnitedStates) who acted as lead writers for the appendices A to E, respectively. The Committee would like also
to thank M. Ermacora (Argentina), H. Bosmans (Belgium), J.-K. Kang (Republic of Korea), E. Vaño
Carruano (Spain), A. Ansari (United States), P. Shrimpton (United Kingdom), O. Holmberg, J. Vassileva
and D. van der Merwe (IAEA) and M. Perez (WHO) for critically reviewing the manuscript. Further, theCommittee acknowledges the contribution of M. Sanagou (Australia) and A. Jahnen (Luxembourg) indeveloping the Committee’s extrapolation model and estimating the related uncertainties. Further,M. Kardan (Islamic Republic of Iran) kindly conducted an additional check on the modelling applied.
Finally, the Committee also expresses its gratitude to the national contact persons and the national experts
who were involved in collecting, submitting, and checking the national data (see also the list below).
The views expressed in the annex remain those of the Committee and do not necessarily represent theviews of the United Nations or its Member States.

Members of Expert Group
Chairs: P. Thomas and A. Wallace (Australia); Members: M. Ermacora (Argentina), R. Smart (Australia),
H. Bosmans (Belgium), H. Järvinen (Finland), E. Nekolla (Germany), K. Akahane (Japan),
D. Kluszczyński (Poland), J.-K. Kang and K-H. Do (Republic of Korea), I. Zvonova (Russian Federation),
E. Vaño Carruano (Spain), I. Suliman (Sudan), A. Aroua and E. Samara (Switzerland), P. Shrimpton(United Kingdom) and G. Ibbott (United States). Observer: M. Perez (WHO).

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87

List of national contact persons and national experts contributors
to UNSCEAR Global Survey on Medical Exposure
Countrycode aCountrynameNational contact persons

National experts

DZA

AlgeriaZ. Mokrani

M. Henni, M. Yaker, N. Sissaoui,
B. Abdeslam, S.E. Bouyoucef

ARG

Argentina

M. Ermacora

P. Menendez, J. Robledo, A.C. Zarlenga,
S. Zunino, A.M. Ema Descalzo, S. Blanco,
C. Caspani, V. Soroa

ARM

Armenia

AUS

Australia

G. Hirth

BGD

Bangladesh

J. Ferdous

BLR

BelarusN. Vlasova

BEL

Belgium

A. Fremout, P. Willems,
Th. Vanaudenhove

BRA

BrazilL. Vasconcellos de Sa

BRN

Brunei Darussalam

BGR

Bulgaria

A. Dimov

A. Balabanova, I. Mihaylova, R. Lazarov,
L. Gotcheva

CAN

CanadaR. Wilkins

J. Burtt, A. Morrison, E. Gutierrez

CHL

Chile

L. Vironneau Janisek

M. Ortiz, C. Sepulveda, J.L. Rodriguez,
G. Chorbadjian, N. Perez

CHN

China

Sh. ZhaoJ. Cheng, B. Yue, Z. Huang, X. Zhao, X. Qi,
H. Liu, Y. Song, Y. Zhang

HRV

Croatia

CYP

CyprusD. Sakkas

CZE

Czech Republic (Czechia)

K. Petrova

B. Kotrčová, J. Vinklář, I. Zachariášová

DNK

Denmark

K. Breddam

A. Holm Fik, S. Albrecht Lassen,
H. Waltenburg

A. Mnatsakanyan
T. Beveridge, P. Marks, P. Thomas,
A. Wallace, I. Williams

L. Fedarushchanka, G. Chizh, I. Tarutin

V. Delano, S. Batista
M. Besar, S. Abd Hamid, J. Khalid, H. Naseer

D. Faj

EST

Estonia

I. Puskar

E. Gerškevitš, M. Kuddu, S. Nazarenko,
K. Tiigi, A. Poksi, P. Ruuge, A. Aavik,
J. Saaring, D. Sutov, M. Vardja, K. Ulst,
J. Subina

FIN

Finland

R. BlyJ. Liukkonen

FRA

FranceC. Étard, A. Isambert

Ch. Le Bihan, J.-L. Godet

DEU

Germany

T. Jung

A. Giussani, E. Nekolla, A. Schegerer

GRC

GreeceE. Papadomarkaki

S. Economides, C.J. Hourdakis,
M. Nikolaou, S. Vogiatzi

HUN

Hungary

G. Sáfrány

R. Elek, N. Fülöp, C. Varadi

88

UNSCEAR 2020/2021 REPORTCountrycode aCountrynameNational contact persons

National experts

ISL

Iceland

J. Gudjonsdottir

IDN

Indonesia

Z. Alatas, E. Hiswara

IRN

Iran (Islamic Republic of)

M. Kardan

IRQ

Iraq

B. Ahmed

S. Abbas, T. Hasan, Z. Khlil, S. Mansur,
G. Mehdi

ITA

Italy

F. Bochicchio

B. Caccia, A. Trianni

JPN

Japan

K. Akahane

H. Mizuno, T. Teshima, H. Numasaki,
K. Ogawa, T. Igarashi, M. Akahane,
K. Nishikawa, M. Hosono, H. Watanabe

KEN

Kenya

A. Omondi Koteng

KWT

KuwaitE. Alfares

LBN

Lebanon

M. Roumie

L. El-Nachef

LTU

Lithuania

J. Ziliukas

V. Grigoniene

LUX

Luxembourg

N. Harpes

S. Joseph, C. Magalahes

MDG

Madagascar

T. Harivony

A. Ahmad, A. Gabrielle, R. Andriamparany,
R. Ndretsamanantenasoa, I. Michella

MYS

Malaysia

T. Solawati bt Tuan Muda

M. Shukry, N. Rashid, N. Zainol Abidin,
F. Hisham

MKD

North Macedonia

MNE

Montenegro

V. Karadinovic

M. Obradovic

NLD

Netherlands

H. Bijwaard

P. Goemans, D. Valk, I. de Waard-Schalkx

NER

Niger

I. KaneD. Abdou, A. Ada, D. M. Issoufou,
I. Adamou Soli, S.O. Mahamadou

NOR

NorwayA. Liv Rudjord

A. Andersen, L.Holth Djupvik, N. Heimland,
E.G. Friberg

PAK

Pakistan

R. Ali Khan

PHL

Philippines

K. Romallosa

V. Parami, E. Ramo, E. Salvacion,
M. Cabrera, B. San Juan, T. Madrid

POL

PolandD. Kluszczyński

R. Dziadziuszko

KOR

Republic of Korea

J.K. LeeK. Pyo Kim

ROURomania

D. Obreja

O. Girjoaba

RUS

Russian Federation

S. Kiselev

A. Vodovatov, I. Zvonova

SMR

San Marino

C. Muccioli

SAU

Saudi Arabia

A. Basfar

SVN

Slovenia

N. JugD. Žontar

A.M. Hernandez Alvarez

C. Alvarez, M. Jesus Munoz, R. Ruiz Cruces,
E. Vaño Carruano, S. Cañete Hidalgo,
M. García Tejedor, A. Rodríguez Pérez,J. López Torrecilla

ESP

Spain

E. Stikova

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATIONCountrycode aaCountrynameNational contact persons

National experts

SDN

Sudan

I. Suliman

N. Ahmed

SWE

SwedenP. Eriksson

M. Alvarez, L. Ideström

CHE

Switzerland

Ph. Trueb

B. Ott

THA

ThailandP. KanchanaT. Chaiwatanarat, A. Krisanachinda,
P. Pasawang, T. Sanghangthum,
T. Phungrassami

TUR

TurkeyS. Turkes Yilmaz

UKR

UkraineV. Chumak

O. Solodiannikova, L. Stadnyk

ARE

United Arab Emirates

J. AlSuwaidi

F. Riaz

GBR

United Kingdom

A. Bexon

USA

United States

M. Mahesh

URY

Uruguay

F. Soca

A. Ansari, V. Holahan

The International Organization for Standardization Country Code 3166 was used in some tables and figures [I22].

89ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

91

APPENDIX A. METHODOLOGY FOR GLOBAL ASSESSMENT OF
MEDICAL EXPOSURE

I. INTRODUCTION
A1.
The Committee has regularly provided information on medical exposure since its first report in1958 [U3]. Since its UNSCEAR 1988 Report [U4], it has attempted to estimate global exposure rather
than simply presenting country-specific data. In addition, the Committee decided to prepare a survey
questionnaire, in cooperation with the World Health Organization (WHO), and to distribute it to all
Member States of the United Nations. The survey aimed to acquire data on medical exposure in addition
to those appearing in the published literature. The survey approach and the cooperation with WHO has
continued to the current evaluation.
A2.
The Committee, since its UNSCEAR 1988 Report [U4], has used the health-care level (HCL)model to estimate the annual number of medical radiological examinations performed using ionizing
radiation, according to the number of physicians per population [M7]. Extrapolation to derive a global
estimate was performed by determining both the population-weighted average frequencies forprocedures and the population-weighted average dose per procedure within each health-care level andthen applying these population-weighted averages to the whole population within each health-carelevel. This approach worked well when the world population was relatively evenly distributed between
health-care levels and when sufficient representative data could be obtained for each health-care level.
In this evaluation, however, 53% of the total population is in countries categorized as HCL I and veryfew UNSCEAR Global Survey data have been received from countries at other health-care levels.
Therefore, alternative approaches were explored, as described in detail in this appendix (section II).

II. FRAMEWORK FOR ANALYSIS
A3.
This evaluation continues the application of approaches used by UNSCEAR in previous
reports [U6, U9] in order to provide continuity in results, and also (a) takes account of updated
dosimetric recommendations from the International Commission on Radiological Protection (ICRP)[I11] and (b) explores improved methods for modelling global medical exposure to establish newbaselines for examining trends in medical exposure in future evaluations. An essential part of theassessment is the requirement to provide estimates of the medical exposure of the global population.

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UNSCEAR 2020/2021 REPORT

A. Dose assessment
A4.
Medical exposure in diagnostic and interventional radiology is routinely characterized in terms of
the physical dose quantities used for monitoring performance in radiology [I1, I16]. These quantities are:−

Entrance surface dose (ESD in mGy);−

Dose-area product (DAP, Gy cm²) for conventional X-ray procedures;−

Volume-weighted computed tomography dose index (CTDIvol, mGy);−

Dose-length product (DLP, mGy cm) for computed tomography (CT) [I17].

Exposure in nuclear medicine and radiation therapy is characterized in terms of administered activity of
the radiopharmaceutical (MBq) and prescribed doses (Gy) to target volumes, respectively [U9]. Whereas
the above dose quantities provide the basis for ensuring the effective delivery of medical exposure,associated radiation risks for diagnostic procedures are determined by mean doses to organs and tissues
via specific risk models. However, such analyses of risk are not in the scope of this evaluation.
A5.
Diagnostic medical exposure can also be summarized for the purposes of broad comparison interms of effective dose, E, although this radiation protection quantity was developed specifically byInternational Commission on Radiological Protection (ICRP) as part of its system for the control ofsources of exposure to ionizing radiation through the application of dose limits, constraints andreference levels for workers and members of the public [I11]. The concept usefully allows thesummation of radiation exposure, whether whole- or partial-body, from internal and external radiation
exposure, and provides a single measure of the dose to a reference person (averaged for age and sex)that is roughly proportional to the total “radiation detriment” from stochastic effects associated with theexposure [W1]. The effective dose, E, is calculated as a weighted sum of the mean absorbed doses (or,strictly, the mean equivalent doses) to those tissues and organs in the body that are prone to radiationinduced cancer or heritable effects, using detriment-related tissue weighting factors specified by the
ICRP [I11]. The tissue weighting factors are simple adjustments based on nominal risk coefficients(relating E to radiation detriment), averaged over all ages and both sexes, calculated for an ICRP
“world population” with Western and Asian components. The sum of the effective doses from aparticular source of exposure to individuals within a population results in the collective effective
dose (S), which provides a measure of population dose normally for radiation protection purposes [I11].
Dividing S by a population size gives the associated per caput dose, which represents the average doseto every member of that population—irrespective of their particular circumstances of exposure.
A6.
Whereas E is a risk-adjusted dosimetric quantity, its intended purpose is for use as a radiation
protection quantity; it is not intended as a measure of risk for specific populations or individuals andshould not be used for epidemiological purposes. However, E can be applied with caution in relation to
medical radiology in order to compare doses between different diagnostic and interventional procedures
or with those from other sources of ionizing radiation when populations are similar with regard to age
and sex distribution [U6].
A7.
In accordance with the above discussion, the effective dose is used with caution here, as inprevious UNSCEAR reports [U5, U6, U9], for the pragmatic evaluation of population doses (ascollective effective doses) and average doses per person (per caput doses) in relation to medical
radiological exposures. The intended purpose is to provide broad, convenient measures of practicesolely for the assessment of trends and comparison between different sources of exposure for the world
population and not the estimation of any risks. In using reported values of E in such an analysis,

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93

however, it should be noted that evolution in the recommendations from the ICRP concerning the
calculation of E (in relation to both tissue weighting factors and also reference anthropomorphic
phantoms) can lead to significant variation in estimates made under different sets of recommendations
for a given type of examination that may amount to some tens of per cent [J6, S14]. The influence onderived values of E arising from changes in tissue weighting factor between recommendations from
ICRP Publications 103 [I11] and 60 [I9] is illustrated in tables A1 and A2 in relation to some common
X-ray examinations [W1] and nuclear medicine radiopharmaceuticals [I10], respectively. In addition,
the ratios presented in table A3 [S14] illustrate the influence on values of both E-103 [I11] and E-60
[I9] derived for some common computed tomography procedures in the United Kingdom that arise
from choice of anthropomorphic reference phantom: the recently-recommended ICRP computational
voxel adult male and female [I12] or the Medical Internal Radiation Dosimetry (MIRD) hermaphrodite
mathematic phantom originally developed by Oak Ridge National Laboratory [C15]. Tables A1–A3
demonstrate that such recent evolution in the ICRP recommendations leads to patterns of change incalculated values of E that differ between types of examination, leading to both increases (ratios >1)
and decreases (ratios <1). These variations serve to further highlight the broad nature of any
comparisons of values of E.
Table A1. Ratio of effective doses calculated using tissue weighting factors in ICRP Publications 103(E-103) and 60 (E-60) for typical X-ray examinations in the United Kingdom [W1]
CT: Computed tomography
Complete examination

Ratio E-103 / E-60

Head (two projections)

1.36

Cervical spine (one projection)

1.00

Chest (one projection)

1.00

Thoracic spine (two projections)

1.03

Lumbar spine (two projections)

0.91

Abdomen (one projection)

0.91

Pelvis (one projection)

0.62

Intravenous urography (five projections)

0.91

Barium swallow

1.07

Barium follow-through0.87

Barium enema

0.73

CT-head0.84

CT-chest

1.14

CT-abdomen

1.09

CT-abdomen and pelvis

0.98

CT-chest, abdomen and pelvis

1.09

A8.
Under ideal circumstances, this review of global medical exposure would assess values ofeffective dose in terms of both E-103 and E-60. Unfortunately, it is likely that the Committee’s present
review of doses from medical exposure includes the collection of values of E that have been derived
following different ICRP recommendations. These data have often been reported without a clear
description of their underlying basis, such that corrections to rationalize all data to the latest ICRP94

UNSCEAR 2020/2021 REPORT

recommendations are not practical. Accordingly, it will be assumed that all reported values of E relate
primarily to E-60 [I9], with any variations in the basis for their computation representing sources ofpotential uncertainty. However, the differing changes observed between particular types of examination(tables A1 to A3) will, to some extent, tend to balance out when considering a mix of examinations inassessing population dose such that the influence of these uncertainties will be reduced.
Table A2. Ratio of effective doses calculated using tissue weighting factors in ICRP Publications 103(E-103) and 60 (E-60) for a range of common nuclear medicine procedures on the basis of E-60 as
calculated in ICRP Publication 128 and E-103 [A6, A7, H5, S14, W1]
CT: Computed tomography; FDG: Fluoro-2-D-deoxyglucose; HDP: Hydroxydiphosphonate;
MAA: Macroaggregated albumin; MAG3: Mercaptoacetyltriglycine; MIBI: Methoxy isobutyl isonitrile
Examination

Radiopharmaceutical

Ratio E-103 / E-60

Tc-MAA

1.27

Tc-HDP

0.70

Tc-MAG3

0.57

Tc-MIBI

0.73

Tl-chloride

0.73

F-FDG

0.90

Perfusion lung scan

99m

Bone scan

99m

Renal scan

99m

Myocardial perfusion scan (rest)

99m

Myocardial perfusion scan
Tumour scan

201

18

Table A3. Ratio of effective doses calculated for the ICRP computational voxel adult (as mean result
for male and female) and a modified MIRD-type hermaphrodite mathematical phantom (HPA18+)
using tissue weighting factors both in ICRP Publications 103 (E-103) and 60 (E-60) for a range oftypical CT examinations in the United Kingdom [W1]
HPA18+ is a modified adult MIRD-type hermaphrodite mathematical phantom [S14]
Examination

Ratio E (ICRP voxel reference adult) / E (HPA18+MIRD)
E-103

E-60

Head

0.93

0.80

Chest

1.41

1.39

Abdomen

1.27

1.15

Abdomen and pelvis

1.23

1.18

Chest, abdomen and pelvis

1.25

1.20

B. Sources of data
A9.
A comprehensive evaluation of annual global medical practice requires information
concerning every radiological procedure performed in the world during a particular year. Under such
ideal circumstances and for the example of diagnostic radiology (similar arguments apply broadly to theother modality categories of medical practice involving exposure to ionizing radiation), the total
number of X-ray examinations performed annually in the world is given by:
𝑁𝑁 = ∑𝑖𝑖,𝑗𝑗 𝑁𝑁𝑖𝑖,𝑗𝑗(A.1)

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

95

where Ni,j is the annual number of examinations of type i carried out in country j and the summation
includes all countries and types of examination.
Similarly, the population dose from diagnostic radiology S (man Sv) is given by:
𝐸𝐸𝑖𝑖,𝑗𝑗

𝑆𝑆 = ∑𝑖𝑖,𝑗𝑗 �𝑁𝑁𝑖𝑖.𝑗𝑗 × 1,000�

(A.2)

where Ei,j is the typical effective dose (mSv) for examination i in country j, and the global per caput
effective dose (mSv) (for world population of size P) is given by:𝑆𝑆

𝐸𝐸per caput = �𝑃𝑃 × 1,000�

1.

(A.3)

UNSCEAR Global Survey data

A10.
As an integral part of its work, the Committee seeks to collect, via the UNSCEAR Global
Survey incorporating a detailed questionnaire, 1 all available national information concerning annual
numbers (Nj) and typical doses (Ej) for each type of diagnostic examination, together with additional
supporting information on national medical imaging practice. For therapeutic exposure, typical doses
are requested more simply in terms of administered activity (MBq) or prescribed doses (Gy).
A11.

The questionnaires used in the recent UNSCEAR Global Survey consist of four parts:−

Part 1: Essential information and data on annual total numbers of examinations andprocedures within each broad type of radiological discipline (such as diagnostic radiology
including all X-rays, all dental examinations, all interventional radiology and all computed
tomography examinations separately), together with total numbers for broad types ofequipment and staffing;−

Part 2: Detailed information on diagnostic and therapeutic equipment and staffing;−

Part 3: Numbers of diagnostic radiological examinations, nuclear medicine procedures (bothdiagnostic and therapeutic) and radiation therapy treatments;−

Part 4: Information of dosimetric data including estimates of effective dose per examination orprocedure.

A12.
The UNSCEAR Global Survey was launched in 2014. To encourage increased participationand secure the collection of available data, particularly from countries that could supply only lessdetailed information, a simplified version of the questionnaire was distributed in 2017. This
questionnaire requested key indicators of practice, including annual totals for national numbers of
examinations of diagnostic and interventional radiology and information on subcategories such as
conventional radiology, dental radiology and computed tomography separately, together with totals forbroad types of radiological equipment and staffing information. Similar key summary was sought inrelation to nuclear medicine procedures and radiation therapy treatments. For further details, see also
the electronic attachments B1 to E1.

1 Available at the country specific webpage on www.survey.unscear.org.

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UNSCEAR 2020/2021 REPORT

Literature review data

A13.
The national data available from the UNSCEAR Global Survey have been supplemented byother information, including reports from national institutes/authorities. The availability of such national
data has been facilitated in Europe by the European Basic Safety Standards Directive [E4] that requires
European Union Member States to periodically monitor population doses. Initiatives on this topic in somecountries have led to the publication of national data supporting assessments of population dose, including
those in Australia [H6], Europe [E5], the United Kingdom [H5] and the United States [N1, N2].
A14.
This evaluation is also supported by useful information reported in the published literature in
relation to various surveys of medical practice. Ideally, these studies should be both robustly conducted
and regionally based. Smaller-scale surveys can be of interest if they provide coherent novel resultsfrom countries for which data are otherwise not available. Dose data reported for particular types of
examination in terms of typical values of physical dose metrics (e.g., ESD, DAP, DLP) were converted
to E using a set of standard dose coefficients included in the user manual for the UNSCEAR Global
Survey [U11].
A15.
The ongoing development of initiatives in monitoring patient exposure, including automateddose assessment and data management systems that support dose registries and databases, will also
facilitate the future collection of data concerning frequency and dose at the national level [L1, R3, R9].

III. APPROACHES FOR GLOBAL ASSESSMENT
A16.
A number of approaches have been explored and several models were applied in performing
the present global assessment of medical exposure. In this section, the HCL model applied in previous
UNSCEAR reports on medical exposure [U4, U5, U6, U9], a model based on an alternativeclassification scheme, and also continuous mathematical models are tested and discussed.
A17.
In the inevitable absence of the comprehensive information required for a complete analysis, it
becomes necessary to undertake extrapolation so that results for the available sample of data can bescaled using an appropriate model in order to derive an assessment of global medical exposure. The
challenge posed by the limited information available from the UNSCEAR Global Survey is illustrated
in table A4, which shows the size (as a percentage of the global population) of the data sample provided
in relation to X-ray, nuclear medicine and radiation therapy procedures for previous evaluations and in
the current evaluation period (2009-2018). Whereas, for example, X-ray data were available in relation
to 63% of the world population for the 1988 evaluation [U4], the sample size decreased during
successive evaluations to only 11% for the 2008 evaluation [U9]; the corresponding sample size in thisevaluation is 43% of the world population, although this figure tends to hide the often limited scope ofthe data available. Corresponding sample sizes in relation to nuclear medicine (diagnostic and therapy)
are 49% and 46%, respectively and 64% of the world population for radiation therapy.

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97

Table A4. Percentage of world population included through national data concerning diagnostic
radiology, nuclear medicine and radiation therapy collected for UNSCEAR periodic evaluations
Reporta

Population in sample (%)aNuclear medicine

World
population(millions) a

X-ray(medical/dental)

Diagnostic

Therapy

Radiation therapy(teletherapy/
brachytherapy)

UNSCEAR 1988 [U4]

63

56

2.8

31

5 000

UNSCEAR 1993 [U5]

60

58

46

46

5 300

UNSCEAR 2000 [U6]

48

51

45

49

5 800

UNSCEAR 2008 [U9]

11

13

10

31

6 500

Current evaluation

43

49

46

64

7 300

Values are rounded.

A18.
Another challenge in making a global assessment on the basis of limited data is the wide
variation between different countries in practice, in relation to the numbers of examinations and their
typical doses. The frequencies of all medical (including dental) radiological examinations reported in
the present sample of countries range from <0.1 to over 2,000 per 1,000 population (representing afactor of over 20,000), which highlights the importance of the particular model used when managing
potential uncertainties in scaling up the results from the survey sample to global practice.
A19.
In developing a model for the global assessment of medical exposure for the UNSCEAR 1988
Report [U4], Mettler et al. [M7] explored the relationships between the national use of radiation in
medicine and other national data that might be more readily available from a wider range of countries.
Correlations between the national annual frequency of diagnostic radiological examinations per 1,000
population and health-care expenditure per caput or number of hospital beds were reported to be “poor”
and “less than optimal”, respectively, whereas a correlation with population per physician was “high”.
A20.
Mettler et al. [M7] assigned countries to four health-care levels in order to estimate theworldwide medical population exposure as follows:−

HCL I with more than one physician for 1,000 population;−

HCL II with one physician for 1,000–2,999 population;−

HCL III with one physician for 3,000–10,000 population;−

HCL IV with less than one physician for over 10,000 population.

A21.
Following the HCL model, all countries are stratified according to the number of physicians
per population on the assumption that this is linked to the medical radiological practice per caput(figure A-I). In this way, relatively similar national data within each HCL category can be pooled toprovide population-weighted average values that can be scaled for total populations within the same
category or for the whole world. This approach of averaging and extrapolating data within one categoryof medical care should lead to smaller uncertainties compared with a simple global average. Population
sizes for each of the four health-care levels are summarized in table A5. Whereas the world population
had grown significantly (by nearly 30%) between the Committee’s reviews for 1988 and 2008, HCL I
countries continued to account for around a quarter of the global population. In contrast, the global
proportion assigned to HCL II countries rose from a third (in 1988) to a half in 2008, with reductionsfor HCLs III and IV countries to proportions of 16% and 12%, respectively, over this period. In the

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UNSCEAR 2020/2021 REPORT

current evaluation, world population has increased by 13% since 2008, with a more significant increasein the proportion in HCL I countries (24 to 53%) and a corresponding reduction for HCL II (49 to31%). Proportions of global population within HCL III and HCL IV are also reduced from their levels
in 2008 (16 to 9% and 11 to 7%, respectively). One contributing factor in this significantly different
pattern is the change in classification for Brazil and China from HCL II in 2008 to HCL I in 2015. Thisoccurrence highlights a limitation in the non-continuous nature of the HCL model.
Figure A-I. Correlation of annual frequency of radiological examinations and physician density [M7]A22.
Limitations in the broad HCL classification system have already been discussed in UNSCEAR
2000 Report [U6] where some flexibility in the practical application of the model was applied. For
example, some countries with relatively large numbers of physicians were classified as HCL II or
HCL III rather than HCL I [U6].

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99

Table A5. Distribution of world population by health-care level
HCL: Health-care level
Distribution of world population in millions (%) a

Reporta

HCL I

HCL IIHCL IIIHCL IVWorld

UNSCEAR 1988 [U4]

1 300
(26%)

1 750
(35%)

1 220
(24%)

730
(15%)

5 000
(100%)UNSCEAR 1993 [U5]

1 350
(25%)

2 630
(50%)

850
(16%)

460
(9%)

5 290
(100%)UNSCEAR 2000 [U6]

1 530
(26%)

3 070
(53%)

640
(11%)

565
(10%)

5 800
(100%)UNSCEAR 2008 [U9]

1 540
(24%)

3 150
(49%)

1 010
(16%)

740
(11%)

6 440
(100%)

Current evaluation

3 910
(53%)

2 250
(31%)

620
(9%)

520
(7%)

7 300
(100%)

Values are rounded.

A23.
The HCL model can be applied, for example, to the sample national data concerning
diagnostic radiology collected by the Committee. If Ni,j is the annual number of examinations of type iin country j (of population Pj), the frequency of examination i per 1,000 population in country j is:𝐹𝐹𝑖𝑖,𝑗𝑗 =𝑁𝑁𝑖𝑖,𝑗𝑗
𝑃𝑃𝑗𝑗

(A.4)

× 1,000

A24.
The weighted average frequency of examination i per 1,000 population in HCL level k (withpopulation PHCL(k)) is then given by:𝐹𝐹𝑖𝑖,𝐻𝐻𝐻𝐻𝐻𝐻(𝑘𝑘) = � �𝐹𝐹𝑖𝑖,𝑗𝑗 ×
𝑗𝑗

𝑃𝑃𝑗𝑗
𝑁𝑁𝑖𝑖,𝑗𝑗
𝑃𝑃𝑗𝑗
� = ��
× 1,000 ×�=
𝑃𝑃𝐻𝐻𝐻𝐻𝐻𝐻(𝑘𝑘)𝑃𝑃𝑗𝑗
𝑃𝑃𝐻𝐻𝐻𝐻𝐻𝐻(𝑘𝑘)∑𝑗𝑗 �𝑁𝑁𝑖𝑖,𝑗𝑗

𝑗𝑗

𝑃𝑃𝐻𝐻𝐻𝐻𝐻𝐻(𝑘𝑘)× 1,000�

(A.5)

𝑃𝑃𝑗𝑗

(A.6)

Similarly, the weighted average typical effective dose (mSv) for examination i in HCL level k is given
by:𝐸𝐸𝑖𝑖,𝐻𝐻𝐻𝐻𝐻𝐻(𝑘𝑘) = ∑𝑗𝑗 �𝐸𝐸𝑖𝑖,𝑗𝑗 × 𝑃𝑃

𝐻𝐻𝐻𝐻𝐻𝐻(𝑘𝑘)�where Ei,j (mSv) is the typical effective dose for examination i in country j.
The population dose (man Sv) from all examinations in HCL level k is then:
𝑆𝑆𝐻𝐻𝐻𝐻𝐻𝐻(𝑘𝑘) = ∑𝑖𝑖 �𝐹𝐹𝑖𝑖,𝐻𝐻𝐻𝐻𝐻𝐻(𝑘𝑘) ×

𝐸𝐸𝑖𝑖,𝐻𝐻𝐻𝐻𝐻𝐻(𝑘𝑘)
1,000

𝑃𝑃

𝐻𝐻𝐻𝐻𝐻𝐻(𝑘𝑘)× 1,000
�(A.7)

The global population dose (man Sv) from all examinations is given by:
𝑆𝑆𝑤𝑤𝑤𝑤𝑤𝑤𝑤𝑤𝑤𝑤 = ∑𝑘𝑘=𝐼𝐼−𝐼𝐼𝐼𝐼 𝑆𝑆𝐻𝐻𝐻𝐻𝐻𝐻(𝑘𝑘)

(A.8)

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UNSCEAR 2020/2021 REPORT

A25.
Absolute numbers of examinations (within each HCL category or for the world) aredetermined from their frequencies and associated populations (equation (A.4)), and per caput doses
from knowledge of population doses and size of populations (equation (A.3)).
A26.
Successful application of the HCL model requires (considering the often incomplete national
data collected) establishment of a consistent set of data, for each HCL category and for the world, inwhich the sum of the frequencies for each type of examination is equal to the total frequency for all
examinations. Thus, the HCL model does not intend to provide estimates of examination numbers,
population dose or per caput effective dose for individual countries. Rather, it provides a robust
assessment of global estimate of medical exposure using ionizing radiation.
A27.
The above analysis should also be viewed in the light of the relative populations in each HCL
category and their overall contributions to global population dose. Whereas HCL I included about aquarter of the world population in 2008 (table A5), it accounted for around 73% of the global dose frommedical X-rays [U9]. Corresponding data for HCL II were around one half and one quarter,
respectively, with HCLs III and IV each providing only 1% towards the global dose (yet accounting forover one quarter of the global population). The present analysis suggests an increasing dominance of
HCL I, with inclusion of about half of the global population. Whereas it is important to have robust datafrom HCLs II-IV in order to report on the range of practice around the world, such data would appear tobe less critical in terms of the assessment of global medical exposure.

A. Classification by income levels
A28.
A possible alternative to classification by health-care levels is to use the World Bank income
classifications for countries [F3]. The World Bank income classification is based on gross national income
per caput (current USD) and has also four levels: high, upper middle, lower middle, and low. Figure A-II
shows the distribution of the global population among these levels (16, 36, 39 and 9%, respectively),
which is more even than the distribution among health-care levels (53, 31, 9 and 7%, respectively).
Figure A-II. Population in millions by each income group [F3]Latest year of data availability during each fiscal year

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101

B. Application to present assessment
A29.
Table A6 presents estimates of the annual number of conventional radiology (excluding
dental) examinations derived using extrapolations of the population-weighted average frequencies in
the assessed data, by the HCL model and by a separate extrapolation of population-weighted averagefrequencies categorized by income level. Also shown are the number of countries for which there weredata, compared with the total number of countries in each category, and the proportion of the total
population in each category covered by the data. These extrapolations yield estimates of 2.39 and 2.47
billion examinations per annum, respectively. It should be noted that for the extrapolation by income
levels, the data for the upper middle-income and lower middle-income groups were combined because
the population-weighted average frequency in the lower middle-income classification was actuallyhigher than that in the upper middle-income classification. The population-weighted average frequency
within the lower middle-income group alone was 370 examinations per 1,000 population and using thisvalue in the extrapolation gives 1,070 million examinations for this category, increasing the overall
projected total by 270 million.
Table A6. Estimates of the global number of conventional radiology (excluding dental) examinations
per annum by extrapolation of population-weighted average frequencies to all countries in eachcategory from assessed data by health-care level and by income level
Based on data from 65 countries (UNSCEAR Global Survey and additional sources) for the period 2009–2018
Category

Population-weighted
average examinations per
1 000 population aCountries
included/all
countries b

Proportion of
population inassessed data (%)

Total
population(millions)

Extrapolated
examinations(millions) a

Extrapolation by health-care levelI

466

60/105

86

3 908

1 823

II

202

1/31

0.1

2 256

455

III

172

3/31

18

622

107

IV

1.9

1/27

4

526

1

Total

326

65/194

48

7 312

2 386

Extrapolation by income level

a

High

867

43/57

96

1 149

997

Upper middle

267 c

15/58

80

2 619

700

Lower middle

267 c

5/45

8

2 882

771

Low

7

2/34

7

662

4.5

Total

338

65/194

48

7 312

2 472

Values are rounded; however extended precision has been preserved to illustrate differences.

b

Member States of WHO.

c

Data for upper middle-income and lower middle-income have been combined. The population-weighted average number ofprocedures for upper middle-income was 256 per 1,000 population and for lower middle-income was 370 per 1,000 population.

A30.
Table A7 presents estimates of the annual number of dental radiology examinations derived
using extrapolations of the population-weighted average frequencies in the assessed data, categorized
by the HCL model and income level. Also shown are the number of countries for which there weredata, compared with the total number of countries in each category, and the proportion of the total
population in each category covered by the data.

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A31.
These extrapolations both yield estimates of 1.19 billion examinations per annum; however,this concordance is dependent on a number of assumptions. There were no data for HCL III andHCL IV; therefore, average frequencies of 20 per 1,000 population and 10 per 1,000 population,
respectively, were assumed in the extrapolation by health-care level. These choices are essentiallyarbitrary but follow a pattern of reducing frequencies at lower health-care levels. The populationweighted average frequency for lower middle-income countries in the assessed data was actually higher(340 per 1,000) than for upper middle-income countries (88 per 1,000). As in the similar case forconventional radiology (excluding dental), the two categories were combined to give an overall
population-weighted average of 94 per 1,000 population. There were also no data for low-income
countries and an average frequency of 10 per 1,000 population was assumed in the extrapolation by
income level. If the actual population-weighted average for lower middle-income countries were used,
the overall total would increase by around 50%, but the increase would be based on the data from only
two countries. Thus, the nominal agreement between the two extrapolations shown in table A7 is highly
dependent on the assumptions made in the absence of data.
Table A7. Estimates of the global number of dental radiology examinations per annum byextrapolation of population-weighted average frequencies to all countries in each category fromassessed data by health-care level and by income level
Based on data from 49 countries (UNSCEAR Global Survey and additional sources) for the period 2009–2018
Category

Population-weighted
average examinations per
1 000 population aCountries
included/all
countries b

Proportion of
population inassessed data (%)

Total
population(millions)

Extrapolated
examinations(millions) a

Extrapolation by health-care levelI

270

48/105

76

3 908

1 057

II

49

1/31

0.1

2 256

111

III

20

c

0/31

0

622

12.4

IV

10d

0/27

0

526

5.3

Total

162

49/194

41

7 312

1 186

Extrapolation by income level

a

High

578

38/57

95

1 149

665

Upper middle

94

e

9/58

71

2 619

247

Lower middle

94e

2/45

2

2 882

272

Low

10f

0/34

0

662

6.6

Total

163

49/194

41

7 312

1 191

Values are rounded; however extended precision has been preserved to illustrate differences.

b

Member States of WHO.

c

Assumed frequency of 20 per 1,000 population applied to HCL III.

dAssumed frequency of 10 per 1,000 population applied to HCL IV.

e

Data for upper middle-income and lower middle-income have been combined. The population-weighted average number of

examinations for upper middle-income was 88 per 1,000 and for lower middle-income was 340 per 1,000.
f

Assumed frequency of 10 per 1,000 population applied to the low-income category.

A32.
Table A8 presents estimates of the annual number of computed tomography examinations
derived using extrapolations of the population-weighted average frequencies in the assessed data,
categorized by health-care level and income level. Also presented are the number of countries for which

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

103

there were data, compared with the total number of countries in each category, and the proportion of thetotal population in each category covered by the data.
A33.
Extrapolation applying the average frequencies across each health-care level yields anestimated annual total of 378 million computed tomography examinations. No data were received fromHCL II countries; therefore, for the extrapolation, a frequency of 20 CT examinations per 1,000
population were assumed for HCL II. As in the similar case for dental radiology, this is a largely
arbitrary choice, though it is broadly consistent with a geometric progression across the health-carelevels. This assumed value accounts for 12% of the extrapolated total of CT examinations for the period
2009-2018. Extrapolation by income levels yields a lower estimate of 346 million examinations perannum. High-income countries average 160 examinations per 1,000 population per annum, upper
middle-income countries 46 per 1,000, and lower middle-income countries 15 per 1,000. Examination
frequency in the single low-income country included in the assessment was 0.2 per 1,000.
Table A8. Estimates of the global number of computed tomography examinations per annum byextrapolation of population-weighted average frequencies to all countries in each category fromassessed data by health-care level and by income level
Based on data from 69 countries (UNSCEAR Global Survey and additional sources) for the period 2009–2018
Category

Population-weighted
average examinations per
1 000 population aCountries
included/all
countries b

Proportion of
population inassessed data (%)

Total
population(millions)

Extrapolated
examinations(millions) a

Extrapolation by health-care levelI

84

63/105

84

3 908

330

II

20 c

0/31

0

2 256

45

III

5.1

3/31

16

622

3.2

IV

0.6

3/27

19

526

0.34

Total

52

69/194

48

7 312

378

Extrapolation by income level

a

High

160

44/57

98

1 149

184

Upper middle

46

15/58

76

2 619

120

Lower middle

15

9/45

10

2 882

42

Low

0.2

1/34

8

662

0.14

Total

47

69/194

48

7 312

346

Values are rounded; however extended precision has been preserved to illustrate differences.

b

Member States of WHO.

c

Assumed frequency of 20 per 1,000 population applied to HCL II.

A34.
Table A9 presents estimates of the annual number of interventional radiology procedures
derived using extrapolations of the population-weighted average frequencies in the assessed data,
categorized by health-care level and by income level. Also shown are the number of countries forwhich there were data, compared with the total number of countries in each category, and the
proportion of the total population in each category covered by the data.

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UNSCEAR 2020/2021 REPORT

A35.
Extrapolation applying the average frequencies across each health-care level yields anestimated annual total of 21.9 million procedures. No data were received from HCL II or HCL IV
countries. For the extrapolation, a frequency of one procedure per 1,000 population was assumed for
HCL II and the frequency for HCL III was applied to HCL IV also. Approximately 90% of theextrapolated total comes from HCL I countries, where the coverage of the assessed data is 81% of the
population. Extrapolation by income levels yields a lower estimate of 18.6 million procedures perannum. High-income countries average 13 procedures per 1,000 population per annum, upper middleincome countries 1.4 per 1,000 and lower middle-income countries 0.13 per 1,000 population. In theextrapolation, the observed frequency of procedures per 1,000 population used for lower middleincome countries was also applied for low-income countries.
Table A9. Estimates of the global number of interventional radiology procedures per annum byextrapolation of population-weighted average frequencies to all countries in each category fromassessed data by health-care level and by income level
Based on data from 57 countries (UNSCEAR Global Survey and additional sources) for the period 2009–2018
Category

Population-weighted
average procedures per
1 000 population aCountries
included/all
countries b

Proportion of
population inassessed data (%)

Total
population(millions)

Extrapolated
procedures(millions) a

Extrapolation by health-care levelI

5.0

55/105

83

3 908

19.5

II

1.0c

0/31

0

2 256

2.3

III

0.13

2/31

14

622

0.08

IV

0.13d

0/27

0

526

0.07

Total

3.0

57/194

46

7 312

21.9

Extrapolation by income level

a

High

13

39/57

93

1 149

14.5

Upper middle

1.4

12/58

78

2 619

3.6

Lower middle

0.13

6/45

8

2 882

0.39

Low

0.13e

0/34

0

662

0.09

Total

2.5

57/194

46

7 312

18.6

Values are rounded; however extended precision has been preserved to illustrate differences.

b

Member States of WHO.

c

Assumed frequency of 1 per 1,000 population applied to HCL II.

dFrequency for HCL III was applied.

eFrequency for lower middle-income level was applied.

A36.
Table A10 presents estimates of the annual number of nuclear medicine procedures derived
using extrapolations of the population-weighted average frequencies in the assessed data, categorized
by health-care level and by income level. Also shown are the number of countries for which there weredata, compared with the total number of countries in each category, and the proportion of the total
population in each category covered by the data. Extrapolation by applying the average frequencies
across each health-care level yields an estimated annual total of 42 million procedures. Extrapolation by
income levels yields a similar estimate of 39 million procedures per annum.

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

105

Table A10. Estimates of the global number of diagnostic nuclear medicine procedures per annum byextrapolation of population-weighted average frequencies to all countries in each category fromassessed data by health-care level and by income level
Based on data from 68 countries (UNSCEAR Global Survey and additional sources) for the period 2009–2018
Category

Population-weighted
average procedures per
1 000 population aCountries
included/all
countries b

Proportion of
population inassessed data (%)

Total
population(millions)

Extrapolated
procedures(millions) a

Extrapolation by health-care levelI

10.3

61/105

84

3 908

40.3

II

0.63

3/31

19

2 256

1.42

III

0.09

1/31

6

622

0.057

IV

0.04

3/27

12

526

0.02

Total

5.7

68/194

52

7 312

41.8

High

26

41/57

96

1 149

29.0

Upper middle

2.6

16/58

79

2 619

6.8

Lower middle

1.0

10/45

21

2 882

2.7

Low

0.03

1/34

3

662

0.02

Total

5.3

68/194

52

7 312

39.0

Extrapolation by income levela

Values are rounded; however extended precision has been preserved to illustrate differences.

b

Member States of WHO.

A37.
Table A11 presents estimates of the annual number of radionuclide therapy treatments derived
using extrapolations of the population-weighted average frequencies in the assessed data, categorized byhealth-care level and by income level. Also shown are the number of countries for which there were data,compared with the total number of countries in each category, and the proportion of the total population ineach category covered by the data. No data were received from HCL IV or low-income countries. Thus,
for the purposes of making the extrapolations, the frequency for HCL III countries was applied to HCL IV
countries and for low-income countries. Extrapolation by applying the average frequencies across eachhealth-care level yields an estimated annual total of 1.5 million radionuclide therapy treatments.
Extrapolation by income levels yields a similar estimate of 1.45 million treatments per annum.
A38.
Table A12 presents estimates of the annual number of radiation therapy treatment courses
derived using extrapolations of the population-weighted average frequencies in the assessed data,
categorized by health-care level (HCL model) and by income level. Also shown are the number ofcountries for which data were compared with the total number of countries in each category and the
proportion of the total population in each category covered by the data.
A39.
Extrapolation applying the population-weighted average frequencies across each health-carelevel yields an estimated total of 6.22 million radiation therapy treatment courses annually. As no data
were available from HCL IV countries, the same frequency as for HCL III was assumed for the
extrapolation. Radiation therapy treatment courses at HCL III and HCL IV countries make only a small
contribution to the global total number of treatment courses. The UNSCEAR Global Survey covered
over 75% of the population in each of the HCL I and HCL II levels. Extrapolation by income levels
yields a slightly lower estimate of 5.88 million treatment courses per annum. High-income countries

106

UNSCEAR 2020/2021 REPORT

average 2,748 treatment courses per million population per annum, upper middle-income countries 923
per million, and lower middle-income countries 105 per million and low-income only 7 per million.
Table A11. Estimates of the global number of radionuclide therapy treatments per annum byextrapolation of population-weighted average frequencies to all countries in each category fromassessed data by health-care level and by income level
Based on data from 41 countries (UNSCEAR Global Survey) for the period 2009–2018
Category

Population-weighted
average treatments per
100 000 population aCountries
included/all
countries b

Proportion of
population inassessed data (%)

Total
population(millions)

Extrapolated
treatments(millions) a

Extrapolation by health-care levelI

29.9

36/105

75

3 908

1.17

II

13.3

4/31

20

2 256

0.30

III

3.9

1/31

6

622

0.02

IV

3.9

0/27

0

526

0.02

Total

20.7

41/194

47

7 312

1.51

c

Extrapolation by income level
High

31.6

24/57

74

1 149

0.36

Upper middle

30.4

12/58

78

2 619

0.80

Lower middle

9.1

5/45

19

2 882

0.26

Low

3.9c

0/34

0

662

0.03

Total

19.8

68/194

47

7 312

1.45

a

Values are rounded; however extended precision has been preserved to illustrate differences.

b

Member States of WHO.
Frequency for HCL III was applied.

cTable A12. Estimates of the global number of radiation therapy treatment courses per annum byextrapolation of population-weighted average frequencies to all countries in each category fromassessed data by health-care level and by income level
Based on data from 44 countries (UNSCEAR Global Survey and additional sources) for the period 2009–2018
Category

Population-weighted
average treatment
courses per million
population aCountries
included/all
countries b

Proportion of
population inassessed data (%)

Total
population(millions)

Extrapolated
treatment
courses(millions) a

Extrapolation by health-care level
I

1 501

37/105

76

3 908

5.87

II

128

5/31

78

2 256

0.288

III

56

2/31

10

622

0.035

IV

56c

0/27

0

526

0.030

Total

979

44/194

66

7 312

6.22

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

Category

Population-weighted
average treatment
courses per million
population aCountries
included/all
countries b

Proportion of
population inassessed data (%)

107

Total
population(millions)

Extrapolated
treatment
courses(millions) a

Extrapolation by income level

a

High

2 748

26/57

86

1 149

3.16

Upper middle

923

11/58

75

2 619

2.42

Lower middle

105

6/45

64

2 883

0.304

Low

7

1/34

4

662

0.0046

Total

805

44/194

66

7 312

5.88

Values are rounded; however extended precision has been preserved to illustrate differences.

b

Member States of WHO.

cFrequency for HCL III was applied.

C. Continuous models
A40.
Experience gained from testing the data received for the UNSCEAR Global Survey has
highlighted significant limitations in the HCL model previously established to provide assessments ofglobal medical exposure. This model uses four health-care levels and relies on an assumed
homogeneity of data within each health-care level. Drawbacks with this approach include thefollowing:−

It relies on having a sufficient sample of national data within each health-care level in order toprovide robust estimates of population-weighted mean values (for frequency and dose) that are
representative for the level;−

It is non-continuous in nature and thus sensitive to movement of countries between health-carelevels , with a risk for over- or underestimation of results if a large country moves from one
level to another;−

There has been a pragmatic need in previous reviews to deal with apparent outliers to thegeneral trend (between national numbers of examinations and physicians), with necessary ad
hoc reclassification of health-care level for some countries;−

Uncertainties, as now required for the Committee’s global evaluations, are difficult to assess.

A41.
To address the deficiencies identified above, the present assessment has used continuous
models to extrapolate the UNSCEAR Global Survey data to the global population. To estimate theglobal population exposure, the frequencies of different medical radiation examinations must first be
estimated. Since only a few countries provided detailed data at the level of examinations/procedures,
broader modality categories of examinations were considered for the global estimation. These were:conventional radiology (excluding dental radiography), dental radiography, computed tomography,
interventional radiology, and nuclear medicine. The frequency estimates for each modality category
were then multiplied by typical dose values to obtain a collective effective dose per category. Although
not relevant for the global population dose estimation, the global frequency of radionuclide therapy andof radiation therapy were also estimated.

108

UNSCEAR 2020/2021 REPORTA42.
For example, in figure A-III, annual frequencies of conventional radiology (excluding dental)
examinations per 1,000 population are plotted against the number of physicians per 1,000 population.
The dashed line shows a least squares fit for a continuous model, a power function (𝐹𝐹 = 𝑎𝑎 ∙ 𝑋𝑋 𝑏𝑏 ), where
F is the procedure frequency, X is the physician density, and a and b are the model parameters. The
coefficient of determination (R2 value) is 0.63, indicating that 63% of the variation in the annual
number of conventional radiology (excluding dental) examinations per 1,000 population is predictablefrom the variation in the number of physicians per 1,000 population.
A43.
Figure A-III also highlights the relative lack of data in relation to HCLs II-IV. Sixty of
65 countries included in the assessment with data regarding overall numbers for conventional radiology(excluding dental) are in HCL I, one country in HCL II, three in HCL III, and one in HCL IV. As aproportion of the total population in the assessed data, countries classified as HCL I represent 96%,
whereas only 4% are categorized as HCL II-IV (3% in HCL III and 1% in HCL IV). This is importantin relation to application of the global HCL model.
Figure A-III. Relationship between density of physicians and annual frequency of conventional
radiology examinations (excluding dental)
Result of a non-linear regression (power function) based on 65 countries (dots, UNSCEAR Global Survey andadditional sources)

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

109

A44.
Computed tomography examinations increasingly contribute to the population dose as theirdose per procedure is relatively high and their frequency continues to rise. Sixty-seven countries areincluded in the frequency data for computed tomography. Figure A-IV shows the annual frequencies ofcomputed tomography examinations per 1,000 population from the UNSCEAR Global Survey versus
number of physicians per 1,000 population. Again, the scattering of the data points is pronounced, andthe fitted model is a continuous power function (coefficient of determination 0.59).
Figure A-IV. Relationship between density of physicians and annual frequency of CT examinations
Result of a non-linear regression (power function) based on data from 67 countries (dots, UNSCEAR Global
Survey and additional sources)

A45.
Whereas diagnostic radiology represents the most significant contributor, with 95% in 2008, of
the global collective dose from all diagnostic medical exposure [U9], the UNSCEAR Global Survey
also seeks to assess worldwide practice in nuclear medicine (accounting for the remaining 5% of global
population dose) and radiation therapy. Scatter plots of procedures versus physician density for
diagnostic nuclear medicine (data from 69 countries) and radiation therapy (data from 45 countries) areillustrated in figures A-V and A-VI, respectively. Overall, patterns are generally similar to thatobserved in relation to diagnostic radiology and computed tomography (figures A-III and A-IV), withcoefficients of determination (R2 values) of 0.74 (nuclear medicine) and 0.67 (radiation therapy), forfitted power function models.

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UNSCEAR 2020/2021 REPORT

Figure A-V. Relationship between number of physicians per 1,000 population and annual number ofnuclear medicine examinations per 1,000 population
Result of a non-linear regression (power function) based on 69 countries (dots, UNSCEAR Global Survey andadditional sources)

A46.
Publicly available data on health-care systems and economical capacities of countries (e.g., [U10,
W7, W10] data from 2015 or the nearest available) have been used to test whether alternative variables are
more appropriate than physician density (per 1,000 population) alone, namely:
−
−
−
−
−
−
−
−
−
−

Life expectancy (years);
Proportion of population aged 0–14 years (%);
Proportion of population aged 65+ years (%);
Skilled health professionals (per 10,000 population);
Medical physicists (per million population);
Health expenditure proportion (%);
Human development index;
Gross domestic product per caput (USD);
Gross national income per caput (USD);
Medical devices (conventional X-ray machines and computed tomography scanners, nuclear
medicine systems, radiation therapy units) per 1,000 population.

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

111

Figure A-VI. Relationship between density of physicians and annual frequency of radiation therapy
treatments
Result of a non-linear regression (power function) based on 45 countries (dots, UNSCEAR Global Survey)

A47.
In order to test the suitability of any of the above parameters to substitute the established healthindicator, one-variable regressions were performed. As in the regression analyses with physician density,
power functions were used. Two examples of the relationship between the submitted data of procedure
frequencies and alternative key indicators are presented in figure A-VII, which shows the density ofskilled health professionals versus annual frequency of conventional radiology examinations (excluding
dental); and figure A-VIII, which shows the density of computed tomography devices versus annual
frequency of computed tomography examinations. The coefficients of determination show higher values
compared to regressions using physician density alone.

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UNSCEAR 2020/2021 REPORT

Figure A-VII. Relationship between density of skilled health professionals and annual frequency of
conventional radiological examinations (excluding dental)
Result of a non-linear regression (power function) based on 65 countries (dots, UNSCEAR Global Survey andadditional data)

A48.
Correlations between the variables listed above were examined using covariance matrix plots
to find variables that correlate so strongly with each other that one of them did not need further
consideration. To make the modelling process as effective as possible, only the variables associatedwith the greatest amount of variance in the observed frequency data were used. The next step was toanalyse how these data were related to the outcome parameters in the UNSCEAR Global Survey (e.g.,frequencies of the different modality categories considered).

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

113

Figure A-VIII. Relationship between density of computed tomography devices and annual frequency
of computed tomography examinations
Result of a non-linear regression (power function) based on data from 67 countries (dots, UNSCEAR Global
Survey and additional data)

A49.
Input variables were also restricted to those for which a large number of values were available
globally. This was the case for all population-related data, but not for all parameters relating to medical
devices or staff (e.g., number of nuclear medicine devices). The lower limit was set at 100 in order toachieve a high coverage of the world population in extrapolations using the resulting models.
A50.
An exploratory analysis of model candidates was performed, including a correlation analysis.
With the help of recursive feature elimination [K17], up to five candidate variables for inclusion in amodel were identified. To keep the resulting model rational for non-specialists, single-variable nonlinear regression and multiple-linear regression techniques were used to select appropriate models forconventional radiology (excluding dental), dental radiology, computed tomography, nuclear medicine
and interventional radiology procedures, and for radionuclide and radiation therapy treatments.
A51.
Further statistical modelling of the procedure frequency data was undertaken using the R and
STATA software packages [S26]. Fitting a model to all the available data leaves no data against whichto assess the predictive capability of the model. Therefore, the available data were randomly split into
separate creation and validation sets. The performance of a model generated from the creation dataset
was assessed against the validation dataset, using the mean squared error as the metric. Models weregenerated in a stepwise fashion with addition or elimination of predictor variables (depending on the

114

UNSCEAR 2020/2021 REPORT

specific method) and tested against the validation dataset, building an assessment of the variation in test
statistics (mean squared error) with the number of variables in the model. In this manner, the modelwith the fewest variables but adequate predictive power could be chosen. Having assessed thesuitability of general model forms by this method, a final fit of the preferred model to the full dataset
was used to generate predictions of procedure frequencies for countries that did not provide data to the
UNSCEAR Global Survey.
A52.
The results of the modelling often indicated that variables other than physician density
provided greater predictive power for the data under consideration. Among these were the humandevelopment index, the density of relevant medical devices (e.g., computed tomography scanner
density when modelling computed tomography examination frequency), and the proportion of the
population in particular age brackets. However, data on some of these indicators were not sufficiently
widely available to be useful in making predictions for all countries worldwide. In general, models
using a simple power function of the physician density were assessed as providing the best balancing ofpredictive power and general applicability.
A53.
As an additional check on the modelling described above, exploratory analyses forconventional radiology (excluding dental) and computed tomography were conducted using an artificial
neural network approach. Artificial neural networks are well-suited for a very broad class of non-linear
approximation [B1, D11], where the appropriate forms of the transfer functions relating the predictor
variables and the response variables are unknown. Neural network models were developed using the
Neural Network Toolbox in MATLAB 8.2 (The Math Works Inc.) [D4]. With these tools, a simple
script can be constructed to load the relevant data from an input file, train and validate the neuralnetwork model, and save the model architecture and performance in an output file [E2]. The results ofthese exploratory analyses gave very similar predictions for the overall number of conventional
radiology (excluding dental) and computed tomography procedures to the simpler approaches describedabove, providing increased confidence in the suitability of the simplified approach.
A54.
The models selected for use in the UNSCEAR global assessment take the form of powerfunctions of the physician density (physicians per 1,000 population). This choice was motivated by the(a) simplicity of the model, (b) satisfactory predictive power, and (c) availability of the data as WHO
publishes these values regularly [W7] and its close relation to the health-care level classification used inprevious UNSCEAR assessments. The general form of the models is:𝐹𝐹𝑖𝑖 = 𝑎𝑎 × (𝑑𝑑𝑖𝑖 )𝑏𝑏(A.9)

where Fi is the procedure frequency in country i, di is the physician density in country i, and a and b are
the model parameters. Two variants are considered: the first with the modelling performed in theabsolute data space, and the second with the parameters a and b determined by linear regression using
log-transformed data (figures A-III to A-VI). These two approaches yield different results as the first
gives equal weight to the absolute differences between the data and the model, while the second gives
equal weight to the relative differences.
A55.
A third, more sophisticated, modelling approach using negative binomial regression [H10] was
examined to test the robustness of the results from the simpler models. Negative binomial regression isa generalization of Poisson regression, in which the variance is allowed to differ from the mean. Thisloosening is used to deal with over dispersion in the model, where the extra variance is presumed to be
due to factors not considered in the model. The functional form of the model is:

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

115(A.10)

𝑙𝑙𝑙𝑙(𝑁𝑁𝑖𝑖 ) = 𝛽𝛽0 + 𝛽𝛽1 × 𝑥𝑥1,𝑖𝑖 + ⋯ + 𝛽𝛽𝑛𝑛 × 𝑥𝑥𝑛𝑛,𝑖𝑖 + ln (𝑃𝑃𝑖𝑖 )where Ni is the count of procedures in country i, {x1,i … xn,i} are the values of predictor variables{x1 … xn} for country i, {β0 … βn} are the parameters of the model and Pi is the population of country i,
the natural logarithm of which is treated as an offset in the model. The covariates included in the final
model varied across the seven broad modality categories, depending on which were found, through abootstrap process, to predict the most variance in each particular case.
A56.
Summary results for the three continuous models described above (power-law in absolute
space, power-law in log space, and negative binomial regression) are shown in table A13. The total
numbers of examinations were derived by combining the submitted data from the survey with thepredictions of the selected model for countries that did not provide data to the analysis. Additional data,
including categorization of the different model results by health-care level and income level, areavailable in electronic attachment A-2. The mean squared error for all models is calculated bycomparison to the absolute values in the assessed data. The model selected for the global evaluation is
the power-law fit in absolute data space. Although the mean squared error for this model is not always
the lowest of the models considered, this model has been chosen because of its simplicity, involving
only a single predictor variable (physician density), its satisfactory predictive power, and the wideavailability of the data for the predictor variable. Aside from these considerations, the predictions fromall models are quite similar.
A57.
For conventional radiography (excluding dental), survey data from 43 countries were includedin the evaluation. After inclusion of data from the EC DDM 2 project [E5] and from other sources, datafrom 65 countries, covering 48% of the total world population, contributed to the assessment. The
model estimates range from 2.1 to 2.6 billion procedures per annum (table A13). With the selected
power-law model fitted in the absolute data space, the total number of conventional radiography(excluding dental) procedures across the world is assessed at 2.6 billion per annum.
Table A13. Predictions of three continuous models tested for estimation of examination/procedure
frequencies for the global assessment by modality categories
Modelling information

ModelPower-law(absolute space) aPower-law(log space)

Negative binomial
regression c

Conventional radiology (excluding dental)
Mean squared error b

111 000

128 000

100 000

Radiography examinations in assessed data
(millions)

1 587

1 587

1 587

Additional radiography examinations from model(millions)

1 039

551

843

Total conventional radiology examinations(millions)

2 626

2 138

2 430

Countries with no prediction (missing data)

1

1

14

Proportion of total population included (%)

99.8

99.8

99.3

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UNSCEAR 2020/2021 REPORTPower-law(absolute space) a

Modelling information

Power-law(log space)

Negative binomial
regression c

Dental radiology
Mean squared error b

50 00059 00033 000Dental radiography examinations in assessed data
(millions)

809

809

809

Additional dental radiography examinations frommodel (millions)

292

246

192

Total dental radiography examinations (millions)

1 101

1 055

1 001

Countries with no prediction (missing data)

1

1

15

Proportion of total population included (%)

99.8

99.8

99.2

Computed tomography
Mean squared error b

2 940

3 090

3 180

Computed tomography examinations in assesseddata (millions)

278

278

278

Additional computed tomography examinations
from model (millions)

125

87

36

Total computed tomography examinations(millions)

403

365

314

Countries with no prediction (missing data)

1

1

9

Proportion of total population included (%)

99.8

99.8

99.4

Interventional radiology
Mean squared error b

45

54

39

Interventional radiology procedures in assesseddata (millions)

16.5

16.5

16.5

Additional interventional radiology proceduresfrom model (millions)

7.1

2.3

1.0

Total interventional radiology procedures(millions)

23.6

18.8

17.5

Countries with no prediction (missing data)

1

1

9

Proportion of total population included (%)

99.8

99.8

99.4

104

111

84

Nuclear medicine procedures in assessed data
(millions)

34.1

34.1

34.1

Additional nuclear medicine procedures frommodel (millions)

5.8

4.5

3.1

Total nuclear medicine procedures (millions)

39.9

38.6

37.2

Countries with no prediction (missing data)

1

1

15

Proportion of total population included (%)

99.8

99.8

99.3

Nuclear medicine (diagnostic)
Mean squared errorbANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATIONPower-law(absolute space) a

Modelling information

Power-law(log space)

Negative binomial
regression d

117

Radionuclide therapy
Mean squared error b

200

228

252

Radionuclide therapy treatments in assessed data
(millions)

0.936

0.936

0.936

Additional radionuclide therapy treatments frommodel (millions)

0.496

0.305

0.539

Total radionuclide therapy treatments (millions)

1.432

1.241

1.475

Countries with no prediction (missing data)

1

1

1

Proportion of total population included (%)

99.8

99.8

99.8

585 000

697 000

622 000

Radiation therapy treatment courses in assesseddata (millions)

4.7

4.7

4.7

Additional radiation therapy treatment courses
from model (millions)

1.5

1.1

0.8

Total radiation therapy treatment courses(millions)

6.2

5.8

5.5

Countries with no prediction (missing data)

1

1

57

Proportion of total population included (%)

99.8

99.8

95.7

Radiation therapy
Mean squared error ba

Selected model for the global assessment.

bMean squared error for all models is calculated by comparison to the absolute value.

c

Using 5 parameters.

dUsing 1 parameter.

A58.
For dental radiography, survey data from 36 countries were included in the assessment. After
inclusion of data from the EC DDM 2 project [E5] and from other sources, data from 49 countries,
covering 41% of the total world population, contributed to the assessment. The estimated results range
from 1.0 to 1.1 billion examinations per annum. The negative binomial regression model is clearly abetter fit to the assessed data. The spread of results is quite narrow, however, and the choice of model
has only a slight impact on the overall result. The selected power-law model fitted in the absolute data
space gives a global annual estimate of dental radiography examinations of 1.1 billion.
A59.
The UNSCEAR Global Survey data for computed tomography were received from43 countries. Additional data on examination frequencies were obtained from the EC DDM 2 project[E5] and from data reported to the OECD [O3]. Further data for HCL III and HCL IV countries weretaken from previous UNSCEAR reports [U6, U9]. The assessment included data from 69 countries,
covering 48% of the total world population. The estimated results range from 314 to 403 million
examinations per annum. The selected power-law model fitted in the absolute data space gives a total
estimate for computed tomography examinations worldwide of 403 million per annum.
A60.
For interventional radiology, data were received from 39 countries. After inclusion of datafrom the EC DDM 2 project [E5] and from previous UNSCEAR reports [U6, U9], a total of
57 countries, covering 46% of the total world population, contributed to the assessment. The estimatedresults range from 17.5 to 23.6 million procedures per annum. The selected power-law model fitted in

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the absolute data space gives a total estimate for interventional radiology procedures across the worldof around 24 million per annum.
A61.
The assessment for diagnostic nuclear medicine procedures included survey data from46 countries. With the addition of data from the EC DDM 2 project [E5] and from previous UNSCEAR
reports [U6, U9], data from 68 countries, covering 52% of the total world population, contributed to theassessment. The estimated results range from 37.2 to 39.9 million procedures per annum. The selected
power-law model fitted in the absolute data space gives a total estimate for diagnostic nuclear medicine
procedures across the world of around 40 million per annum.
A62.
For radionuclide therapy treatments, survey data were received from 41 countries, covering
47% of the total world population. The estimated results range from 1.2 to 1.5 million treatments perannum. The selected power-law model fitted in the absolute data space gives a total estimate forradionuclide therapy treatments across the world of 1.4 million per annum.
A63.
The assessment for radiation therapy treatment courses included data from 44 countries,
covering 66% of the total world population. The estimates range from 5.5 to 6.2 million procedures perannum. The selected power-law model fitted in the absolute data space gives a total estimate for thenumber of radiation therapy treatment courses across the world of 6.2 million per annum.
A64.
The modelling results are consistent with the extrapolation results shown earlier. Thisconsistency supports the overall totals adopted from the modelling. In some cases, e.g., for dental
radiography and for computed tomography, the consistency of the categorical extrapolations with themodelling results is dependent on assumptions made in the absence of data. This demonstrates theadvantages of the modelling approach over extrapolation by categories when there are no or only few
data for some categories. The modelling results for HCL IV and for low-income countries are notably
higher than the extrapolation results, suggesting that there may be some overestimation. However, theextrapolation results at these levels are dependent on data from only one or two countries and, thus,
must be considered very unreliable. In any event, the assessed number at these levels is a very minor
component of the overall analysis.
A65.
In summary, the Committee selected a continuous model for examination frequencies in theseven general modality categories based on power-law fits in the absolute data space with physician
density as the only predictor variable. The total numbers of examinations per modality category
reported in the current evaluation were derived by combining the submitted data from the survey withthe predictions of the selected model for countries that did not provide data to this analysis.

IV. ANALYSIS OF UNCERTAINTIES
A66.
Previous UNSCEAR reports [U6, U9] have not quantified the effect of limitations in themodel used to evaluate global practice for medical exposure. However, the Committee recognizes theimportance of including estimates of likely uncertainties in relation to its global assessments ofnumbers of examinations and population doses. Accordingly, an appropriate methodology wasdeveloped for the purpose of addressing uncertainties in relation not only to the national data but also to
the model used for their extrapolation to global practice.
A67.
A framework for the assessment of uncertainty in relation to estimates of collective dose wasdeveloped and is presented in detail in the electronic attachment A-1. Sources of uncertainty in the

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119

estimation of medical exposure and a standard methodology for their assessment were applied in thisappendix. This methodology could also be applied at a national level before countries submit their data
for UNSCEAR surveys of global practices.
A68.
Hart and Wall [H4], assessed the per caput effective dose from X-rays to the United Kingdom
population in 1997/1998 at 0.33 mSv and estimated the related uncertainties as 9% (±0.03 mSv). Suchmethods for uncertainty analysis were also discussed in detail by the EC DDM 2 project [E5] andformed the basis for the uncertainty estimate of ±6% quoted in relation to the per caput effective doseof 1.06 mSv assessed for the European population from X-ray procedures [E5]. Zontar et al. [Z1] also
assessed the uncertainty in a national estimate of collective effective dose in Slovenia as ±11%
(1 standard deviation). Such additional information would support the provision of robust estimates of
uncertainty in relation to estimates of worldwide medical exposure.
A69.
Given that complete information on a country’s population dose, Sj (man Sv), with countryspecific estimates of uncertainty, uj, would be available for every country j in the world, an estimate ofuncertainty, Uworld, in the global population dose could easily be assessed following the rules of
propagation of uncertainties (see also electronic attachment A-1):(A.11)

𝑈𝑈𝑤𝑤𝑤𝑤𝑤𝑤𝑤𝑤𝑤𝑤 = �∑𝑗𝑗 𝑢𝑢𝑗𝑗 2

A70.
Applying the HCL model to assess the global population dose, the uncertainty Uworld can be
estimated as follows. The uncertainty ui,HCL(k) in the weighted average frequency of examination i per
1,000 population in HCL k, Fi,HCL(k) (see equation (A.5)), is𝑢𝑢𝑖𝑖,𝐻𝐻𝐻𝐻𝐻𝐻(𝑘𝑘) = �∑𝑗𝑗 �𝑢𝑢𝑖𝑖,𝑗𝑗

𝑃𝑃𝐻𝐻𝐻𝐻𝐻𝐻(𝑘𝑘)2(A.12)

� × 1,000

where ui,j is the absolute uncertainty in the annual number of examinations of type i in country j, Ni,j and
PHCL(k) is the population in HCL k.
A71.
The uncertainty vi,HCL(k) (mSv) in the weighted average typical effective dose for examination iin HCL k, Ei,HCL(k) mSv (see equation (A.6)), is given by𝑣𝑣𝑖𝑖,𝐻𝐻𝐻𝐻𝐻𝐻(𝑘𝑘) = �∑𝑗𝑗 �𝑣𝑣𝑖𝑖,𝑗𝑗 ×

𝑃𝑃𝑗𝑗

𝑃𝑃𝐻𝐻𝐻𝐻𝐻𝐻(𝑘𝑘)�2(A.13)

where vi,j (mSv) is the absolute uncertainty in the typical effective dose for examination i in country j,
Ei,j (mSv), Pj is the population in country j and PHCL(k) is the population in HCL k.
A72.
The uncertainty, wHCL(k) (man Sv) in the population dose from all examinations in HCL k,
SHCL(k) man Sv (see equation (A.7)), is then:
𝑢𝑢

2

𝑣𝑣

2

𝑃𝑃

𝐻𝐻𝐻𝐻𝐻𝐻
𝑤𝑤𝐻𝐻𝐻𝐻𝐻𝐻(𝑘𝑘) = �∑𝑖𝑖 �𝐹𝐹𝑖𝑖,𝐻𝐻𝐻𝐻𝐻𝐻(𝑘𝑘) � + �𝐸𝐸𝑖𝑖,𝐻𝐻𝐻𝐻𝐻𝐻(𝑘𝑘) � × 1,000,000
𝑖𝑖,𝐻𝐻𝐻𝐻𝐻𝐻(𝑘𝑘)𝑖𝑖,𝐻𝐻𝐻𝐻𝐿𝐿(𝑘𝑘)(A.14)

A73.
Ignoring the uncertainty associated with the HCL model, the uncertainty, Vworld (man Sv)
associated with the estimate of the global population dose from all examinations, Sworld (man Sv),
derived by the HCL model can be estimated by:
𝑉𝑉𝑤𝑤𝑤𝑤𝑤𝑤𝑤𝑤𝑤𝑤 = �∑𝐼𝐼𝐼𝐼
𝑘𝑘=𝐼𝐼 �𝑤𝑤𝐻𝐻𝐻𝐻𝐻𝐻(𝑘𝑘) �2(A.15)

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If the uncertainty, Umodel, associated with the HCL model is also taken into account, the uncertainty inthe global population dose, Uworld (man Sv), is given by:
𝑉𝑉

2

𝑈𝑈𝑤𝑤𝑤𝑤𝑤𝑤𝑤𝑤𝑤𝑤 = �(𝑈𝑈𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚 )2 + � 𝑆𝑆 𝑤𝑤𝑤𝑤𝑤𝑤𝑤𝑤𝑤𝑤 � × 𝑆𝑆𝑤𝑤𝑤𝑤𝑤𝑤𝑤𝑤𝑤𝑤
𝑤𝑤𝑤𝑤𝑤𝑤𝑤𝑤𝑤𝑤(A.16)

A74.
Assuming that the countries that contributed data to this survey also provided information on
the relative uncertainty, urel,j, of their frequency data, one can estimate the absolute uncertainty for the
total number of examinations from all submitting countries, Usurvey, as follows:
𝑈𝑈𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠 = �∑𝑗𝑗 𝑢𝑢𝑗𝑗 2(A.17)

where 𝑢𝑢𝑗𝑗 is the absolute uncertainty assessed from the relative uncertainty and the examination frequency
for each country.
A75.
To estimate the uncertainty in the total number of examinations and the global annual
collective effective dose using the selected continuous model, the following approach was adopted: forthe uncertainty in the total number of examinations for countries that submitted data, equation (A.17)
was first applied to the five modality categories as outlined above, i.e. for conventional radiology
without dental examinations (A), dental radiology (B), computed tomography (C), interventional
radiology (D) and nuclear medicine (E), giving the uncertainties Usurvey(i) (i=A, …, E). With these, theuncertainty in the total number of examinations in the survey data, Usurvey, can be estimated:
𝑈𝑈𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠 = �∑𝑗𝑗=𝐴𝐴,…,𝐸𝐸 𝑈𝑈𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠(𝑗𝑗) 2(A.18)

𝑈𝑈𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚 = �∑𝑗𝑗=𝐴𝐴,…,𝐸𝐸 𝑈𝑈𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚(𝑗𝑗) 2(A.19)

A76.
Second, the uncertainty in the total number of examinations from the modelling for all
modality categories was estimated, using the square root of the mean squared error from the modelling
results as the estimated absolute error in the calculated examination frequency. If Umodel(i) (I=A, … , E)
is the uncertainties for the five modality categories, then the uncertainty of the total number of
examinations in the modelling data, Umodel, can be estimated as follows:

A77.

Finally, the uncertainty in the global estimate of the number of examinations, Uglobal, is
𝑈𝑈𝑔𝑔𝑔𝑔𝑔𝑔𝑔𝑔𝑔𝑔𝑔𝑔 = �𝑈𝑈𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠 2 + 𝑈𝑈𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚 2(A.20)

A78.
Estimates of uncertainties in dose metrics were provided by some countries in theirsubmissions to the UNSCEAR Global Survey. The survey included options to provide data on thevariation in the relevant practical dose quantity as well as the resulting effective dose and also included
the option of recording the size of the sample used to derive this data. Countries commonly reported themean dose and the sample standard deviation as the indication of the level of variation. While thestandard error calculated by dividing the sample standard deviation by the square root of the sample
size is a formal estimate of the standard uncertainty in the mean dose for a particular examination orprocedure, this quantity only represents the precision to which the mean dose is determined and does
not necessarily reflect the uncertainties introduced by applying the mean dose as an estimate of the dose
for all such examinations. As discussed in the electronic attachment A-1, following the approach
proposed in the EC DDM 1 project [E3], uncertainties (one standard deviation) in the dose per
examination can be taken to vary from about ±7% (for a large sample size and well-matched conversion
coefficients) to around ±25% (for a small sample size and poorly-matched conversion coefficients). InANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

121

the extreme, when local data is unavailable and data from another country is used as an estimate, an
uncertainty of ±50% is recommended.
A79.
As described in the annex, for countries that did not provide data to the UNSCEAR Global
Survey, a frequency-weighted dose per examination or procedure in a given modality category was
ascribed and the collective effective dose was estimated by multiplying the estimated total number of
examinations or procedures in the modality category by the frequency-weighted dose. For all suchcases the uncertainty in the dose was taken to be ±50%, as recommended for the “Foreign data only”
category in the electronic attachment A-1. For countries that did provide data to the UNSCEAR Global
Survey, the stated uncertainties were used where provided. If the only data provided were the sample
standard deviation and the sample size, estimated uncertainties ranging between 10% and 50% wereapplied, depending on the stated sample size and the relative sample standard deviation.
The uncertainties in the overall estimates of collective effective dose were not very sensitive to theuncertainties assigned to the data for each country. This is due to a combination of the averaging effectof deriving the uncertainty in a sum over many parts and the fact that the uncertainties in the estimatesof the number of examinations or procedures were generally larger and tended to dominate the overall
uncertainty estimated.
A80.
The relative uncertainty of the collective dose for each procedure category, Urel,D(i), is
calculated by the relative uncertainty of the frequency, urel,fr(i), and the relative uncertainty of the dose,
urel,D(i), per procedure estimate (i=A, …, E), where urel,D(i) was estimated by the standard error of themean of the doses per procedure category from the survey:
𝑈𝑈𝑟𝑟𝑟𝑟𝑟𝑟,𝐷𝐷(𝑖𝑖) = �𝑢𝑢𝑟𝑟𝑟𝑟𝑟𝑟,𝑓𝑓𝑓𝑓(𝑖𝑖) 2 + 𝑢𝑢𝑟𝑟𝑟𝑟𝑟𝑟,𝐷𝐷(𝑖𝑖) 2 (i = A, …, E)(A.21)

giving the absolute uncertainties, UD(i), of collective dose per procedure category by multiplying Urel,D(i)with the collective dose of each category (i=A, …, E).
A81.

The absolute uncertainty of the global collective dose, Ucol_D, is then
𝑈𝑈𝑐𝑐𝑐𝑐𝑐𝑐_𝐷𝐷 = �∑𝑗𝑗=𝐴𝐴,…,𝐸𝐸 𝑈𝑈𝐷𝐷(𝑗𝑗) 2(A.22)A82.
In summary, standard uncertainties for the total number of examinations in each category of
medical radiological exposure were derived by combining the estimated standard uncertainties for
examination counts included in country submissions to the UNSCEAR Global Survey with the standard
uncertainties in the predictions of the selected continuous models, which were based on the square rootof the mean squared error from the modelling. Uncertainties in the average doses per procedure were
derived from the UNSCEAR Global Survey data when provided and were otherwise assumed to be±50%. These were combined with the standard uncertainties for the numbers of examinations to derive
the overall standard uncertainty in the collective effective dose for each modality category. Finally, theuncertainties in the modality categories were combined to obtain an uncertainty estimate for the global
total collective effective dose. Taking twice the standard uncertainty as an estimate of the overall
uncertainty, the ranges for the total number of examinations and the total collective effective dose are
estimated as ±30%. Table A14 summarizes the uncertainties derived for the global estimates offrequencies and collective effective doses by modality categories.

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Table A14. Relative uncertainties for the global estimates of frequencies and collective effective
doses by modality
Values are rounded to the nearest 1%. Uncertainties are expressed as 2-standard deviations
Modality category

Uncertainties of frequency
estimates (%)

Uncertainties of collective
effective doses estimates (%)

Conventional radiology (excluding dental)

36

42

Dental radiology

58

68

Computed tomography

40

44Interventional radiology

80

88

Nuclear medicine

72

76

Radionuclide therapy

32

Not applicable

Radiation therapya

26

Not applicable

Total

28

30

a

a

Not included in the total.

V. SUMMARY
A83.
The Committee previously used a categorical HCL model to derive data on examination
frequencies and doses and to then extrapolate the data into a global evaluation of medical radiological
exposure. In the present assessment, however, 53% of the total population is in countries classified as
HCL I and very few survey data were received from countries in other HCL levels. Therefore, analternative approach was adopted, constructing mathematical models of the observed variation in
examination frequencies and using these models to predict the expected practice in countries that did
not supply data. In this assessment, continuous models of examination frequencies within seven broad
modality categories have been developed to generate projections for countries that did not provide data
for the UNSCEAR Global Survey. The modality categories used in this assessment were conventional
radiology (encompassing projection radiography, radiography and fluoroscopy but excluding dental
radiology), dental radiology, computed tomography, interventional radiology, nuclear medicine,radionuclide therapy, and radiation therapy.
A84.
A continuous model, which takes the form of a power function of the physician density(physicians per 1,000 population) in each country, was selected. This choice was made because of theavailability of the data, as WHO regularly publishes such values provided by its Member States, and theclose relation of the model to the HCL classification used in previous UNSCEAR reports [U6, U9].
More sophisticated modelling involving multiple parameters was also performed, yielding similar
results and, thus, supporting the predictions of the single-parameter model. The results from the singleparameter power function were selected for the evaluation due to their uncomplicated interpretation, thesatisfactory predictive power of the model, and the wide availability of the data. The new continuous
modelling approach has advantages over the former categorical approach when there are no or only few
data for some modality categories. The total numbers of examinations reported in the current
assessment were derived by combining the submitted data from the UNSCEAR Global Survey with thepredictions of the selected continuous model for countries that did not provide data to the survey.

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123

A85.
In this assessment, an alternative to the HCL classification, the World Bank income
classification, was used to present the results of the extrapolation. The World Bank classification isbased on gross national income per caput (current USD) and has also four levels: high, upper middle,
lower middle and low. An advantage of using the World Bank classification is the possibility ofcomparing medical exposure with other health indicators as WHO uses the same classification in theirhealth statistics.
A86.
A framework for evaluating the uncertainties in the UNSCEAR global assessment has beenoutlined and applied. The estimated uncertainty in the total number of medical radiologicalexaminations is ±30% and the estimated uncertainty in the total collective effective dose is also ±30%.

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125

APPENDIX B. LEVELS AND TRENDS OF EXPOSURE IN
DIAGNOSTIC RADIOLOGY

I. INTRODUCTION
B1.
Diagnostic radiology consists of two main imaging modalities (a) conventional radiology
including projection radiography (without contrast media) and radiography/fluoroscopy (mostly with
contrast media); and (b) computed tomography. For each of these modalities, 16–19 subgroups or typesof examinations have been defined in the user manual for the UNSCEAR Global Survey [U11] for datareporting and collection, with “other (please specify)” used as the last category in each modality. The
subgroups are generally similar to the broader modality categories defined by the European
Commission Dose Data Med projects (EC DDM) [E3, E5]. As shown in the literature reviews below,
there have not been uniform classification systems, or systems consistent with the UNSCEAR Global
Survey, when collecting data and publishing the results of examination frequency or population dosestudies. These differences in classification create some difficulties when comparing published data withsubmissions to the UNSCEAR Global Survey, or when comparing published country data.
B2.

Medical exposure in any country or region depends on many factors such as:−

Availability of radiological imaging facilities and appropriately trained staff (e.g., radiologists,
radiographers, medical physicists);−

Types of radiological examinations requested by the referring physicians;−

Types of radiological systems (e.g., proportion of screen-film systems, computed radiology
and full digital radiology systems, image-intensifier and flat-panel detectors) and theircapabilities (e.g., over- or under-couch, continuous fluoroscopy versus pulsed fluoroscopy,
tube current modulation versus fixed tube current, iterative reconstruction) and, thus, theexposure parameters required during the procedures;−

Level of optimization applied in imaging protocols (e.g., consideration of patient size);−

Protocols chosen for the particular examinations/procedures (e.g., adult versus paediatric);−

Patient demographics (e.g., size and weight, proportions of adult and paediatric patients);−

Methodology chosen for estimating the collective effective dose in general and the related
uncertainties in estimating frequencies of examinations/procedures and typical effective doses
per examination/procedure (e.g., sample sizes, national survey versus reimbursement systems);−

Tissue weighting factors used for the calculation of the effective dose according to therecommendations of the International Commission on Radiological Protection (ICRP 60 [I9]or ICRP 103 [I11]);−

Types of radiological examinations/procedures considered for a modality; differinginterpretations are probable for conventional fluoroscopy and interventional radiology (e.g.,
fluoroscopy or diagnostic interventional procedure followed by a therapeutic procedure or only
therapeutic interventional procedures).

126

UNSCEAR 2020/2021 REPORT

B3.
It is clear from above that, among other factors, both the imaging technology and the local
choices for imaging practice can affect the trends in the numbers of examinations and patient doselevels. The impact of technology is discussed more in connection with the trends (section B.VII).
B4.
The following analysis with summaries for diagnostic radiology procedures is based on the
results of the UNSCEAR Global Survey and a comprehensive review of the published literature during
the past decade. The results of the survey provide up-to-date information on examination frequencies,
typical effective doses and staffing and equipment levels in several countries, supplemented withinformation on the age and sex distributions of examination frequencies in some countries. However,
the results of the survey are not complete enough to estimate or summarize the collective effective
doses to population or effective doses per caput for these countries. The results of the literature review
provide relatively recent data for comparison with the current survey data, including publishedinformation on collective effective doses in some countries. The results of both the survey and theliterature review enable identification of the diagnostic radiology examinations that make the highest
contribution to the frequencies, typical effective dose and collective effective doses, and also someanalysis of the recent trends in frequencies and doses and in the related technology.
B5.
The results presented in this appendix reflect mainly the situation in the countries that
submitted data to the UNSCEAR Global Survey (see also electronic attachment B-1) and publishednational surveys. The results have been used (a) for specific prediction models for the global
assessment (more details in appendix A and electronic attachment A-3), and (b) for comparison andtrend analyses presented here.

II. RECAPITULATION OF PREVIOUS UNSCEAR REPORTS
B6.
According to the UNSCEAR 2008 Report [U9], using the health-care level (HCL) model,
approximately 3.6 billion diagnostic radiology X-ray examinations (including dental examinations)were undertaken annually worldwide in the period 1997–2007. The 24% of the population living in
HCL I countries receive approximately two thirds of these examinations.
B7.
The annual frequency of diagnostic medical examinations (excluding dental radiology) in
HCL I countries was estimated to have increased from 820 per 1,000 population in 1970–1979 [U6] to
1,332 per 1,000 population in 1997–2007 [U9]. Comparative values for HCL II countries exhibited aneven greater relative increase, from 26 per 1,000 in 1970–1979 to 332 per 1,000 in 1997–2007. Most of
the increase for HCL I and II countries occurred in 1997–2007. The estimated annual frequency of
diagnostic medical examinations in HCL III and HCL IV countries had remained fairly constant overthis period although, since data for these countries were limited, considerable uncertainty was
associated with this estimate. Globally, for HCL I to HCL IV countries there were, on average, justover 488 diagnostic medical examinations and 74 dental examinations per 1,000 population.
B8.
Also according to the UNSCEAR 2008 Report [U9], there were wide variations in diagnostic
medical examinations between different HCL countries. For example, diagnostic medical examinations
were over 66 times more frequent in HCL I countries than in HCL III and HCL IV countries. Thechange in annual frequency of diagnostic medical examinations reflected changes in population
demographics, as most medical exposure applied to older “patients”.
B9.
In the UNSCEAR 2008 Report [U9], computed tomography accounted for 7.9% of the total
number of diagnostic medical examinations in HCL I countries, and just over 2% in HCL II countries.

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION127

For diagnostic dental examinations, the annual frequency had remained relatively constant for HCL I
countries, at 275 per 1,000 population, compared with 320 per 1,000 population in the 1970–1979
survey. Over this period, there had been a substantial increase in the annual frequency of diagnostic
dental examinations in HCL II countries, rising from 0.8 per 1,000 population in 1980–1984 to 16 per
1,000 population in 1997–2007.
B10.
In the UNSCEAR 2008 Report [U9], the annual collective effective dose to the populationfrom diagnostic medical radiological examinations was estimated to be (a) 2,900,000 man Sv for HCL I
countries; (b) 1,000,000 man Sv for HCL II countries; (c) 33,000 man Sv for HCL III countries; and(d) 24,000 man Sv for HCL IV countries. The total annual collective effective dose to the global
population from diagnostic medical examinations was estimated to be 4,000,000 man Sv. Since the
UNSCEAR 2000 Report [U6], there had been a rise of approximately 1,700,000 man Sv. This increase
resulted partly from an increase in the annual frequency of diagnostic medical radiologicalexaminations, an increase in the per caput effective dose per examination (from 0.4 to 0.62 mSv) and anincrease in the global population (from 5,800 million to 6,446 million).
B11.
The UNSCEAR 2008 Report [U9] estimated an average value of the annual per caput effective
dose across the global population as 0.62 mSv, with 1.9 mSv, 0.32 mSv and 0.03 mSv in HCL I,
HCL II and HCL III/IV countries, respectively. The contribution of computed tomography scanning to
the total collective effective dose due to medical examinations was 47% in HCL I countries and 15% in
HCL II countries, respectively. Globally, on average, the contribution of computed tomography to thetotal collective effective dose due to diagnostic medical radiology was 43%, having increased from
34% in the UNSCEAR 2000 Report [U6]. In contrast, exposure from dental examinations accounted forless than 1% of the total collective effective dose.
B12.
More specifically, the typical effective doses for chest radiography and mammography
decreased significantly, while that for computed tomography decreased only slightly since the previous
UNSCEAR reports [U6, U9]. The introduction of new imaging techniques, including computed
tomography and digital imaging was anticipated to increase the population dose globally in the future.

III. FREQUENCIES OF RADIOLOGICAL EXAMINATIONS
B13.
This section presents information on the frequencies and distributions of diagnostic
radiological examination resulting from the submissions to the UNSCEAR Global Survey (2009-2018)
and from the review of published literature.

A. UNSCEAR Global Survey data
B14.
In the current UNSCEAR Global Survey, essential information (selected main groups of
examination frequencies, numbers of professionals and diagnostic radiological systems and devices)from 51 countries with more detailed information (frequency and dose data) from 30–33 countries havebeen received for diagnostic radiology. However, only 11 countries have submitted information on age
and sex distributions with incomplete dose information.

128

UNSCEAR 2020/2021 REPORT

B15.
The total frequencies per 1,000 population for diagnostic radiology (projection radiography
including dental procedures, radiography and fluoroscopy and computed tomography) obtained fromthe UNSCEAR Global Survey is shown in figure B-I. Detailed frequency information obtained fromthe UNSCEAR Global Survey for projection radiography including dental examinations, radiography
and fluoroscopy and computed tomography are summarized in tables B1 to B3.
B16.
There are great variations of the diagnostic radiology frequencies per 1,000 population
between the countries involved. The frequency of diagnostic radiology examinations makes by far thehighest contribution (97.8%) to the total frequency of medical imaging per 1,000 population: the meanfrequency of diagnostic radiology procedures was 1,038 per 1,000 population, with the range from 311
to 2,414 procedures per 1,000 population.
B17.
In projection radiography, dental examinations make the highest contribution to the totalfrequency of this group (28.7%), while also chest-thorax (20.2%) and limbs and joints (18.2%) also
make high contributions; all the other types of projection radiography examinations contribute less than
6% of the total; the contribution of mammography is 3.1% and screening mammography 5.3%. In
radiography and fluoroscopy, coronary angiography makes the highest contribution (16.3%) to the totalof this modality, followed by examinations of gastrointestinal tract (barium studies) (14.0%) andurogenital tract (5.4%); miscellaneous examinations (“others”: 38.6%) are excluded because in many
countries, this category includes examinations from the other categories not reported separately. In
computed tomography, head examinations (skull and facial bones and soft tissue and brain altogether)make the highest contribution (26.3%) followed by chest (thorax: 12.2%) and abdomen (11.9%).
Compared with the total frequency per 1,000 population for all three diagnostic radiology modalities,
on average, all radiography and fluoroscopy (without dental) is 61.6%, dental is 23.2% and computed
tomography is 12.9%.
Figure B-I. Total frequency per 1,000 population for diagnostic radiology (projection radiography,
radiography and fluoroscopy, and CT) by countries reported to UNSCEAR Global Survey
Only countries having submitted data for all three modalities are includedTable B1a. Annual frequencies per 1,000 population for different projection radiography examinations reported to UNSCEAR Global Survey
Examination frequency per 1 000 population a,b
Total
projection
radiographyc

Head (skull
and facialbones)

Head(soft
tissue)Neck(cervical
spine)

Australia

928

16

1.7

Belarus1 311

Belgium

Chest(thoracic spine)

Chest (shoulder
girdle and ribs)

Mammography

Mammography(screening)

26

116

4.3

36

24

41

36

17

758

19

17

13

1 083

4.8

12

192

8.9

48

92

41

Brazil

284

9.3

6.6

47

2.7

9.8

13

39

Bulgaria

502

19

20

169

9.2

10

21

Cyprus

314

18

172

9.1

0.5

18

Czech Republic

1 450

51

39

233

25

49

10

36

Denmark

507

1.3

4.1

117

7

24

21

51

Estonia

350

15

6.5

0.2

25

30

58

Finland

936

22

63

France

1 083

Germany

0.04

0.02

Neck (softtissue)

1.6

0.03

187

4

26

18

15

15

151

5.8

33

78

1 232

36

31

170

15

41

26

Greece538

18

Iceland502

6.6

Iran (Islamic Republic of)

407

20

Japan

1 571

Lithuania

1 872

26

Luxembourg

1 087

6.3

Netherlands

511

22

Norway1 364

Philippines

279

14

Poland

936

26

162
0.01

4.3

0.01

27

33

60

153

5.3

80

20

28

8

54

45

0.02

0.5

225

77

65

14

7.8

121

7.4

8.9

130

5.2

198

1.3

223

16

20

5.4
35

0.05

0.2

6.1

35

10

28

34

27

22

59

64
3.4

0.3

0.04

7.5

29

129

0.02

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

Chestthorax

Country

130

Examination frequency per 1 000 population a,b
Head (skull
and facialbones)

Head(soft
tissue)Neck(cervical
spine)

Neck (softtissue)Chestthorax

Chest(thoracic spine)

Chest (shoulder
girdle and ribs)

Mammography

Mammography(screening)

Republic of Koread

4 933

75

46

203

7.6

963

24

309

46

296

Romania

517

15

19

118

12

21

Russian Federation

1 306

57

22

219

15

22

Slovenia

361

188

17

46

Spain

795

36

267

28

69

20

Sweden

291

0.5

3.1

61

2

17

140

Switzerland

969

3.3

8.4

143

5.6

22

16

United Arab Emirates

1 624

33

7.4

48

12

869

16

29

15

6.9

United Kingdom

1 027

2.1

0.08

5.6

0.3

158

3.2

16

11

40

United States

1 866

4.2

342

7.8

37

122

15

a

Values are rounded; however extended precision has been preserved to illustrate differences.

b

Zero values are indicated when available; otherwise, cells have been kept empty.

cValues as reported; may not equal sum of all categories.

dValues reported are projections per 1,000 population; not examinations per 1,000 population. Examinations often include more than one projection.

38

UNSCEAR 2020/2021 REPORT

Total
projection
radiographyc

CountryTable B1b. Annual frequencies per 1,000 population for different projection radiography examinations reported to UNSCEAR Global Survey
Examination frequency per 1 000 population a,b
Lumbarspine

Lumbo-sacral
joint only

AbdomenPelvis andhips (bone)

Limbs andjointsWhole spine(trunk)Skeletal survey(head andtrunk)

Dentalintraoral

Dentalpanoramic

OthersAustralia

20

2.1

12

72

188

0.2

1.2

302

59

8.3

Belarus

30

12

26

152

185

44

Belgium

22

23

76

0.8

227

3.8

254

63

Brazil

1.8

4.8

9.5

0.07

62

0.05

65

3.2

Bulgaria

23

15

23

7.5

104

62

19

Cyprus

26

26

17

5.8

22

Czech Republic

42

11

31

61

282

1.8

420

117

Denmark

16

2.3

3.2

46

173

1.6

Estonia

22

6.8

14

80

0.02

Finland

23

5.5

34

173

1.4

France

40

22

77

202

8.8

Germany

56

19

64

257

0.1

Greece34

19

78

Iceland

13

11

40

178

Iran (Islamic Republic of)

18

18

38

Country

10

1

0.02

34

161

Luxembourg

34

Netherlands

4.1

0.02

297

69

13

1.2

385

39

10

339

140

4.1

128

37

1.8

0.3
187

58

13

66

243

6.6

22

13

40

149

1.5

Norway

19

8.5

53

Philippines

2.1

12

8.9

31

Poland

56

12

22

224

1.1

5.3

0.2

411

120

832

357

362

94

13

1.5

1 048

27

0.2
224

60

995

88

131

71

0.9

41

59

0.8

26
4.4

0.9

34

Japan
Lithuania

0.8

14

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

0.4

Pelvis(soft tissue)

Lumbo-sacral
joint only

AbdomenPelvis andhips (bone)

Republic of Korea

374

65

219

Romania32

1.1

Russian Federation

Pelvis(soft tissue)

Limbs andjointsWhole spine(trunk)

132

1 524

48

11

19

90

26

8.2

22

144

Slovenia

54

20

37

Spain

48

42

50

Sweden9

1.8

34

Switzerland

17

9

42

United Arab Emirates

81

16

62

26

United Kingdom

8.5

0.3

15

United States

35

38

Skeletal survey(head andtrunk)

38

Dentalintraoral

Dentalpanoramic

Others

386

181

35

92

67

19

191

211

503

22
22
71

243

6

1

107

43

34

119

1.1

0.3

539

74

63

178

916

64

a

Values are rounded; however extended precision has been preserved to illustrate differences.

b

Zero values are indicated when available; otherwise, cells have been kept empty.

2.7

404

227

44

UNSCEAR 2020/2021 REPORT

Lumbarspine

Country

132

Examination frequency per 1 000 population a,b

Table B2a. Annual frequencies per 1,000 population for radiography and fluoroscopy examinations with contrast media reported to UNSCEAR Global Survey
ERCP: Endoscopic retrograde cholangiopancreatography; IVU: Intravenous urography
Examination frequency per 1 000 population a,bCountry

Total,cGastrointestinal

Biliary tract

Urogenital tract

Barium studies

Defecography

Cholangiography

ERCP

Cholecystography

IVU

Kidney, bladder and urethra

0.1

0.05

0.4

0.3

0.6

1.2

30.8

4.3

Belarus19.3

9Belgium

33.1

1

Brazil0.9

0.02

Bulgaria

24.6

6.5

Cyprus

9.6

4.4

Czech Republic

45.6

2.4

Denmark

11.5

1.5

Estonia

11.1

Finland

4
4.4

0.1

1

0.2

0.3

1.6
0.1

1.9

0.1

0.3

0.1

1.3

1.1

3.2
1.8

0.02

0.1

0.1

2.6

0.2

1

9.6

1.2

0.2

France11.1

2.5

Germany

41.1

2.6

0.6

Greece

4.9

0.7

0.07

0.1

0.2

1

Iceland

18.1

4.6

0.1

3.1

1.3

1.2

Lithuania

64.9

Luxembourg

94

0.1

0.05

0.7

2.9

Netherlands

12.3

0.02

1.5

Norway9.6

2.8

Philippines

1

0.5

Poland

10.5

1.6

Republic of Korea

46.4

25

0.1

2.5

0.6

1.2
1.2

0.2
0.8

0.6
0.02

0.3

0.5

2.4

7.4

0.6

0.7
1.1

0.01

0.2

0.2

0.2

0.01

0.07

0.04

0.1

2.1
2.5

0.09

1.6

133

0.4

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

Australia

Total,c

Gastrointestinal
Barium studies

Biliary tract

Defecography

Cholangiography

ERCP

Urogenital tract
Cholecystography

Romania

32.1

6

Russian Federation

13.1

7.2

0.9

Slovenia

6.1

1

1.3

Spain

10.7

5.3

2.8

Sweden

8.3

2.5

1.7

Switzerland

17.8

0.8

1

United Arab Emirates

10

3.7

United Kingdom

10.6

2.7

United States

24

10

a

0.07

IVU
1.2

0.3
0.2

Values are rounded; however extended precision has been preserved to illustrate differences.

b

Zero values are indicated when available; otherwise, cells have been kept empty.

cValues as reported; may not equal sum of all categories.

0.2

0.8

Kidney, bladder and urethra

0.02

0.2

2

1.1

0.2

0.4

2

UNSCEAR 2020/2021 REPORTCountry

134

Examination frequency per 1 000 population a,b

Table B2b. Annual frequency per 1,000 population for radiography and fluoroscopy examinations with contrast media reported to UNSCEAR Global Survey
Examination frequency per 1 000 population a,bCountry

Australia

Myelography

0.1

Arthrography

1.6

Angiography

OthersCerebralCardiacThoracic

Abdominal

PelvicPeripheral

0.2

11

0.4

0.5

0.3

1.2

Belarus

6.3

BelgiumBrazil0.08

Bulgaria

0.6

6.6

1

0.9

0.12

0.2

0.04

0.04

0.1

2

0.3

6.2

Cyprus

0.07

15

0.03
4.9

0.01

Estonia
0.01

0.1

5.3

0.04

34

0.8

0.07

0.3

6

0.08

0.03

1.3

3.4

0.4

1.2

0.1

0.68

5.4

0.1

1.5

0.1

0.06

0.2

23

135

Denmark

0.07

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

0.03

0.8

5.6

0.2

3.8

0.4

4.6

France

0.4

0.6

0.3

2.5
0.02

0.1

0.9

3.9

Germany

0.6

19

Greece

0.03

1.8

0.2

5.7

Iceland0.5

1.9

Czech Republic

Finland

9

0.06

1
1.9

0.9

2

7.9
0.1

0.07

0.2

0.03

1.1

0.3

0.05

0.2

0.2

71.9

1.2

0.1

2.8

3.7

0.4

0.02

Lithuania
Luxembourg

0.09

10.2

0.2

4.3

Netherlands

0.1

0.71

0.01

1.3

Norway0.2
5.7

Philippines
PolandRepublic of Korea
Romania4.1

0.7

Myelography

Arthrography

Angiography
CerebralCardiac

Russian Federation

3.6

Slovenia

3.8

Spain

2.6

Sweden4.2

Switzerland

6.4

United Arab Emirates
United Kingdom

0.03

Thoracic

Abdominal

1.8

0.06

0.2

0.4

0.1

2.3

0.09

0.03

a

Values are rounded; however extended precision has been preserved to illustrate differences.

b

Zero values are indicated when available; otherwise, cells have been kept empty.

Peripheral

9.5

0.2

7.7

Pelvic1.1

0.6

United States

Others

0.1
0.05

0.07

3.1
4.2

UNSCEAR 2020/2021 REPORTCountry

136

Examination frequency per 1 000 population a,b

Table B3a. Annual frequency per 1,000 population for different computed tomography examinations reported to UNSCEAR Global Survey
CT: Computed tomography
Examination frequency per 1 000 population a,b
Total cCT-head(skull andfacial bones)

CT-head(soft tissue
and brain)

CT-neck(cervical
spine)

CT-neck(soft tissue)

CT-chest(thoracic
spine)

CT-chest(thorax)

CT-abdomen(lumbar spine)

CTabdomen(abdomen)CT-abdomen(liver, pancreas,kidneys)Australia

157

19

21

7.8

2.8

0.9

17

19

1.1

0.02

Bangladesh

155

Belarus78

16

Belgium

201

50

Brazil51

2.4

Bulgaria

58

Canada

153

Chile

115

Cyprus86

15

Czech Republic

105

4.1

32

2.3

1.8

0.4

16

4

12

10

Denmark

161

5.1

23

2.3

5.4

0.5

46

1.2

41

22

Estonia

166

44

3.4

3.6

1

25

5.4

7.1

0.8

Finland

80

0.4

1.8

2.2

0.1

9.9

0.7

10

2.5

France

130

32

3

26

16

6.2

Germany

129

40

4.8

2.3

25

11

22

Greece

79

16

2.3

1.3

0.7

19

4.8

32

Hungary229

Iceland

182

12

36

3.7

6

1.1

48

5.8

45

Iran (Islamic Republic of)

29

Japan

221

Lithuania

96

7.7

18

9.6

7.7

15

18

11

Country

5.6
17
7.4

26

42

6.9

3.2

8.5

3.6

29

0.6

6.8

8.9
13

12

14

3.6

11

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

2.2

1

7.3

137

Total c

CT-head(skull andfacial bones)

CT-head(soft tissue
and brain)

CT-neck(cervical
spine)

47

14

CT-neck(soft tissue)

CT-chest(thoracic
spine)

CT-chest(thorax)

CT-abdomen(lumbar spine)

CTabdomen(abdomen)

33

30

49

CT-abdomen(liver, pancreas,kidneys)

Luxembourg

204

Malaysia

61

Netherlands

85

North Macedonia

31

Norway173

Philippines

31

10

13

0.3

0.4

0.2

3.1

0.2

2.9

0.6

Poland

83

33

2.2

2.1

0.9

0.6

13

4.2

16

0.07

Republic of Korea

163

6.7

32

4.5

4.5

4.5

38

4.5

38

16

Romania

84

31

3.4

0.51

9.3

2.3

8.7

Russian Federation

58

21

1.4

1

12

2.4

8.4

San Marino

136

Saudi Arabia

40

Slovenia

54

24

1.4

3.2

6.3

Spain

88

22

7.5

0.3

14

12

16

Sweden

124

4.8

36

4.6

1.1

24

2.5

43

Switzerland

120

3.5

22

United Arab Emirates

106

14

28

3.4

0.9

2.1

7.8

United Kingdom

91

26

21

1.5

0.7

0.3

3

United States

238

22

47

a

d

5.7

17

23

32

6.6

Zero values are indicated when available; otherwise, cells have been kept empty.

cValues as reported; may not equal sum of all categories.

d

Not included in the modelling due to late submission.

32

39

1.5

8.8

28

Values are rounded; however extended precision has been preserved to illustrate differences.

b

22

31

5.7

4.2

9.2

14

0.5

1.9

2.2
62

UNSCEAR 2020/2021 REPORTCountry

138

Examination frequency per 1 000 population a,b

Table B3b. Annual frequency per 1,000 population for different computed tomography examinations reported to UNSCEAR Global Survey
CT: Computed tomography
Examination frequency per 1 000 population a,bCountry
Australia

CT-pelvis(pelvic bones)

CT-pelvis (pelvic soft
tissue and vascular)

CT-pelvis(pelvimetry)CT-full spine (neck,chest, abdomen)

CT-trunk (chest,
abdomen, pelvis)

CT-limbs

CT-dental

CBCT-dental

1.7

27

0.02

1.3

12

8.9

0.1

18

19

0.8

CBCT-others

Bangladesh
BelarusBelgiumBrazil7.4

2.1

Bulgaria

4.9

0.6

7.4

8.9

24

2.6

6.4

4.5

0.1

0.07

0.8

5.9

0.01

7.7

2.1

0.05

11

2.5

4.9

9.5

0.8

1.4
1

Chile
CyprusCzech Republic

1.4

Denmark

1.6

Estonia

0.3

0.5

Finland

0.7

1.2

France32

Germany

6.7

Greece

0.6

0.09
0.8
4.5

0.5

2.6

6.7
0.5

0.8

6.6

0.04

Hungary
Iceland5

0.04

Iran (Islamic Republic of)
Japan
7.7

2.6

0.8

2.6

139

Lithuania

4

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

CanadaCT-pelvis(pelvic bones)

CT-pelvis (pelvic soft
tissue and vascular)

CT-pelvis(pelvimetry)CT-full spine (neck,chest, abdomen)

Luxembourg

CT-trunk (chest,
abdomen, pelvis)

CT-limbs

CT-dental

4.3

12

4.4

CBCT-dental

CBCT-others

Madagascar
Netherlands

1.4

5.1

3.2

North Macedonia
NorwayPhilippines

22
0.06

0.1

4.3
0.01

0.04

0.1

PolandRepublic of Korea

0.5

Romania
Russian Federation

5

0.1
1.4

5.7

8.6

6.3

1

2.6

2.3

San Marino
Saudi Arabia
Slovenia

0.5

Spain

9.2

Sweden1.7

Switzerland

6.7

United Arab Emirates

1.7

1.8

United Kingdom

1.1

4.9

7.3

0.2

4

0.09
2

0.9

United Statesa

Values are rounded; however extended precision has been preserved to illustrate differences.

b

Zero values are indicated when available; otherwise, cells have been kept empty.

2.6

10

4.2

0.2

1

0.9

12

1.6

1.2

20

0.9

5.2

16

0.07

UNSCEAR 2020/2021 REPORTCountry

140

Examination frequency per 1 000 population a,b

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION141

B. Literature review data
B18.
The frequency per 1,000 population of diagnostic radiological examinations and populationdose from such procedures were reported in 28 peer-reviewed articles, corresponding to 22 countries(one country reported only regional values) and one region of several countries (Europe). These articles
are summarized in table B4. Diagnostic radiology and interventional radiology procedures weregrouped together as X-ray procedures in table B4 because not all publications made a clear distinction
between radiography and fluoroscopy and interventional procedures.
B19.
An exact comparison of data is difficult due to the difference in the studies; however, highincome countries like Germany, Republic of Korea, Switzerland and the United States seem to have thehighest frequencies of X-ray examinations (over 1,200 per 1,000 population). In contrast, low-income
countries like Kenya and North Macedonia are lower with typically less than 200 per 1,000 population.
B20.
In most countries, the population dose from medical exposure is higher than the global
average, while the population dose from medical exposure in some countries now are the greatest
human-made contributor to the population dose (e.g., in Australia [H6] and the United States [N1]).
B21.
The contributions of computed tomography examinations to the total frequencies (medical
radiological examinations) vary substantially: the mean contribution is 9% with the range from 0.7 to
25.5% (about 36-fold variation), compared with 12.9% with the range from 3.2 to 30% (about ninefold
variation) in the current survey. The contributions of computed tomography examinations to totalfrequencies are typically much lower than their contribution to the total collective effective dose:
namely, on average 52.5%, range from 5.3 to 79% (about 15-fold variation). Dental examinations are
typically 10–40% of the total frequency of diagnostic examinations, with a mean value of 23.5%(compared with 23.2% in the current survey) but contribute less than 1% to the total collective effective
dose. Conventional fluoroscopy is typically a few per cent of the total frequency of diagnostic
examinations, with a mean value of 2.8%, but the mean contribution to the total collective effective
dose is 9.7% (1.1–28.6%). Interventional radiology is typically less than 1% of the total frequency but
the mean contribution to the total per caput effective dose is 8.2% (0.5–23%).
B22.
Under the EC DDM 2 project [B20, E5], population dose was estimated in 36 European
countries (28 European Union Member States and eight other European countries) between 2007 and2010 for all diagnostic examinations/procedures (diagnostic radiology, interventional radiology andnuclear medicine) and the results were used to obtain the European averages shown in table B4.
However, only five countries (Bulgaria, Finland, Germany, Switzerland and United Kingdom)
performed a comprehensive evaluation including all diagnostic examinations/procedures, while allother countries based the medical exposure estimation on the TOP 20 methodology as introduced in the
EC DDM 1 project [E3], which focuses on the 20 examinations contributing most to the collective
effective dose and typically underestimates by 20–30%.

Year (period)

Annual number per 1 000 population (frequency) of diagnostic
examinations and interventional procedures a,b

Population dose of diagnostic and interventional procedures
per caput effective dose (mSv) a,b

X-ray

Nuclear medicine

Total cX-ray

Nuclear medicine

Total cReference

Australia

2010

370

20.2

390d

1.59

0.11e

1.70

[H6]

Bulgaria

2010

513

2.6

516

0.41

0.009

0.42

[E5]

Finland

2008

1 197

5.6

1 202

0.45

0.03

0.48

[B19, E5]

France

2007

1 151

18.5

1 170

1.16

0.13

1.3

[E10]

2012

1 247

1.6

[D10]

2010

0.6

0.2

f

[E11]

Germany

2009

Ireland2010–2013

Italy

2006

Kenya

2011

82

Republic of Korea

2013

4 579hLuxembourg

2002

Macedonia (The former
Yugoslav Republic of)

2010

142

0.25d

Norway

2002

742

1.09

Portugal

2010

830

0.96

Romania2012

274

Russian Federation

2015

1 397

Slovenia

2011

2 098 (980)

0.65 (0.60)

[Z1]

Sudan

2010

326

0.18

[S24]

Switzerland

2003

1.2

[A8]

g

j

1 437

35.7

f

1 472

1.67

0.08

1.75

[E5]

0.49

0.05

0.55

[O1]

1.07

[C12]

0.05
12.7

4 592h

1.39h

0.15

1.54h

[L3]

1 366

1.83

0.15

1.98

[S12]

d

i

2008

1 667

2013

1 219

0.85

275

2.8

1 400

9.4

[K13]

i

1 677

[G3]
[B25]
0.08

1.04

d

[T3]

0.371

0.00250.3735

[G5]

0.51

0.009

0.52

[B6]

d

i

1.18
1.4

0.047

i

1.23

[E5]
[L2]

UNSCEAR 2020/2021 REPORTCountry142

Table B4. Evaluation of medical exposure for diagnostic and interventional radiology and nuclear medicine procedures published since the UNSCEAR 2008 Report [U9]Country

Annual number per 1 000 population (frequency) of diagnostic
examinations and interventional procedures a,b

Population dose of diagnostic and interventional procedures
per caput effective dose (mSv) a,b

X-ray

Nuclear medicine

Total cX-ray

Nuclear medicine

Total cReference

Taiwan, China

2008

733

13.6

746

0.64

0.10

0.74

[C6]

United Kingdom

2008

746

8.5

755

0.39

0.025

0.42

[E5]

2009–2012

1 218 (1 000)

Ukrainej
United States

Europe (36 countries)aYear (period)

1.06 (0.95)

2006

1 221

k

64

2016

1 102i42

2007–2010

[S22]

1 285

2.2

k

0.8

3

[N1]

1 144i

1.8

0.4

2.2

[N2]

1.05

0.05

1.10

[B20]

Values are rounded; however extended precision has been preserved to illustrate differences.

b

Zero values are indicated when available; otherwise, cells have been kept empty.

cValues as reported; may not equal sum of all categories.
TOP 20 examinations only.

eExcluding contribution from PET examinations; 0.12 mSv if PET is included.

fPaediatric examinations only.

g

Emilia-Romagna región.

hExcluding interventional procedures; calculation with ICRP 103 tissue weighting factors [I11].

i

I:Excluding dental examinations.

j

J:Extrapolated number, TOP 20 value in parenthesis.

k

K: Excluding dental bitewing and full-mouth procedures (500 million images across whole population, per caput effective dose about 0.01 mSv).

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

d

143

144

UNSCEAR 2020/2021 REPORT

B23.
As with the differences between modality categories (projection radiography with and without
dental, radiography and fluoroscopy and computed tomography), the most frequent individual types ofprocedures can be different from the procedures that make the highest contribution to the collective
effective dose. In Norway, Borretzen et al. [B25] showed that radiography of the thorax (twoprojections) is often the most frequent procedure undertaken in projection radiography while it provides
a low contribution to the collective effective dose. General radiology of the pelvis/hips has similar
characteristics while the difference is less notable. Contributions to the collective effective dose bydental radiography (excluding dental cone beam computed tomography) are also very small or almost
insignificant (typically less than 1%), while their frequency can be among the highest. Computed
tomography examinations in general, and computed tomography of abdomen, thorax and pelvis inparticular, provide high collective effective dose contributions in spite of the relatively low procedure
frequency [B25].
B24.
Other published data from several countries are in general agreement with the example from
Norway. In Taiwan, China a study by Chen et al. [C6] indicated that conventional chest X-rays
contributed most to total frequency (33%) followed by dental (periapical) X-rays (8.6%), while thorax
and abdomen computed tomography contributed most to the total collective effective dose (29.4 and15%, respectively). In France, Étard et al. [E10] studied conventional radiography and concluded thatchest and limbs examinations were the most frequent (29.8 and 26.3%, respectively), while thecollective dose was due mainly to abdominal and pelvic examinations (41.5 and 29.8%, respectively).
However, in low-income countries, trends can be different. Korir et al. [K13] showed that in Kenya thelargest contributors to the total collective dose, in decreasing order, were conventional radiography,
computed tomography, fluoroscopy, interventional radiology and mammography.

IV. TYPICAL EFFECTIVE DOSES PER PROCEDURE

A. UNSCEAR Global Survey data
B25.
The typical (mean) effective dose for each radiological imaging procedure is needed to
calculate the population dose (collective effective dose to population or per caput effective dose), in
addition to the frequency of the procedure and the population number. While the typical effective dose
for a representative number of procedures can be determined by rather sophisticated methods (e.g.,based on Monte Carlo calculations), the most common approach is to convert its value from therepresentative typical (mean) value of dosimetric quantities (mainly dose area product (DAP) or dose
length product (DLP)) with the help of a conversion factor based on a large number of publishedstudies. In the current UNSCEAR Global Survey, consistent values of conversion factors have been
applied as shown below, mostly taken from the user manual for the UNSCEAR Global Survey [U11].
Due to this practice, only the typical effective dose will be reported and not the typical values of
dosimetric quantities.
B26.
From the 51 countries submitting data for diagnostic radiology examinations (projection
radiography, radiography and fluoroscopy and computed tomography) in the survey, only some of them
(1–28 countries depending on the type of examination) have submitted either the typical effective dose
directly or the typical value of the dosimetric quantity (DAP: in projection radiography and radiography

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

145

and fluoroscopy, and DLP: in computed tomography) for the calculation of typical effective dose using
a conversion factor. Many countries, however, have submitted frequencies but no data for doses(neither effective doses nor DAP or DLP values) for many examinations. For most countries, dose data
were not complete for some types of diagnostic radiology examinations.
B27.
Table B5 summarizes the typical (mean) effective doses submitted by countries to UNSCEAR
Global Survey for the different projection radiography examinations, including both the effective doses
directly submitted and the values calculated from the submitted DAP values by a conversion factor. The
conversion factors used in the calculation are shown in table B6. DAP with a conversion factor has beenused to calculate the typical effective dose whenever the DAP has been submitted. The mean value oftypical effective dose, for each type of projection radiography examination, is shown in table B7.

146

Table B5a. Typical mean effective doses (mSv) for projection radiography examinations

Mean effective doses (mSv) per examination a,bCountry

Head (skull andfacial bones)

Head (softtissue)Neck (cervicalspine)

Neck(soft tissue)

Chest-thorax

Chest(thoracic spine)

0.01

0.1

0.15

0.21

0.79

Australia

0.06

0.07

Belarus

0.07

0.08

Belgium

Chest (shoulder
girdle and ribs)

0.09

0.15

Bulgaria

0.06

Czech Republic

0.15

Mammography(screening)

1.60

1.60

0.35
0.30

0.17

Brazil

Mammography

0.10

0.11

0.85

0.66

0.60

0.27

0.05

0.24

0.18

0.18

0.12

0.03

0.32

0.16

0.31

Denmark

0.05

Estonia

0.02

0.01

0.03

0.03

0.06

0.40

0.02

0.40

0.15

0.45

0.06

0.30

France0.08

0.30

Germany

0.03

0.30

Greece

0.04

0.02

0.13

Iceland

0.02

0.13

0.05

0.58

Lithuania

0.12

0.04

0.29

Luxembourg

0.09

0.18

0.07

0.45

Malaysia

0.10

0.17

0.04

0.51

0.18

0.08

0.49

0.15

0.10

0.10

0.10

0.80

0.60

Romania

0.07

0.07

0.08

0.17

0.23

Russian Federation

0.10

0.14

0.30

0.70

0.25

Saudi Arabia

0.04

0.15

0.08

0.20

0.13

0.05

0.36

NorwayPoland

1

0.25

0.16
0.05

2.50

2.30

0.14

0.60

Republic of Korea

Slovenia

0.41

0.20

UNSCEAR 2020/2021 REPORTThe effective doses were calculated from reported DAP values, using conversion factors, or were directly reported values (in italics)

Mean effective doses (mSv) per examination a,bCountry

Head (skull andfacial bones)

Head (softtissue)Neck (cervicalspine)

Neck(soft tissue)

Chest-thorax

Chest(thoracic spine)

Spain

0.06

0.07

0.06

0.48

Sweden

0.04

0.1

0.03

0.60

Switzerland

0.08

0.10

0.06

0.60

0.03

0.01

0.12

0.08

United Arab Emirates
United Kingdom

0.15

a

Values are rounded; however extended precision has been preserved to illustrate differences.

b

Zero values are indicated when available; otherwise, cells have been kept empty.

Chest (shoulder
girdle and ribs)

Mammography

Mammography(screening)

0.27

0.26

0.30

0.30

0.40

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION
147

148

The effective doses were calculated from reported DAP values, using conversion factors, or were directly reported values (in italics)
Mean effective doses (mSv) per examination a,bCountry

Lumbar spine

Lumbo-sacral
joint only

AbdomenPelvis andhips (bone)

Australia

0.62

0.56

0.36

Belarus

1.65

0.71

0.48

Belgium

2.49

0.57

0.65

Brazil0.92

0.30

Bulgaria

0.53

Czech Republic

0.86

Denmark

0.90

Estonia

0.14

France

0.15

0.49

0.47

0.38

0.45

Pelvis (softtissue)Limbs andjointsWhole spine(trunk)

0.019

1.50

Dentalintraoral

Dentalpanoramic

0.006

0.07

0.03

0.02

0.39
0.1

0.09

0.005

1.90

1.60

0.800

0.002

1.60

Germany

1.20

0.55

0.40

0.08

1.50

Greece

1.32

0.33

0.001

Iceland

1.8

1.10

0.64

0.02

Lithuania

0.62

0.34

0.58

Luxembourg

1.14

Malaysia

0.18

NorwayPoland

0.15

0.06

0.50

0.004

0.03

0.003

0.02

0.003

0.02

0.46
0.86

0.34

0.61

1.37

1.27

0.55

1.30

0.80

0.60

0.01

0.01

0.44

Republic of Korea
Romania

0.32

Russian Federation

1.40

Saudi Arabia

Skeletal survey(head andtrunk)

0.33

0.02

0.35

0.42

0.046

0.004

0.80

0.74

0.01

0.01

0.17

0.33

0.02

UNSCEAR 2020/2021 REPORT

Table B5b. Typical mean effective doses (mSv) for projection radiography examinations

Mean effective doses (mSv) per examination a,bCountry

Lumbar spine

Lumbo-sacral
joint only

AbdomenPelvis andhips (bone)

Slovenia

0.68

0.44

0.57

Spain

0.80

0.52

0.58

Sweden

0.85

0.92

0.48

Switzerland

1.50

0.80

0.80

United Arab Emirates

0.03

0.04

0.005

United Kingdom

0.72

1.13

0.53

0.45

a

Values are rounded; however extended precision has been preserved to illustrate differences.

b

Zero values are indicated when available; otherwise, cells have been kept empty.

Pelvis (softtissue)Limbs andjointsWhole spine(trunk)Skeletal survey(head andtrunk)

Dentalintraoral

Dentalpanoramic

0.01

0.008

0.004

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION
149

150

UNSCEAR 2020/2021 REPORT

Table B6. Conversion factors used in effective doses calculation from DAP values for projection
radiography examinations
Examination type

Conversion factor(mSv/(Gy cm2))

Selection of the conversion factor

Head (skull and facialbones)

0.14

Selected to yield the mean effective dose (mean of submitted
typical values) from the mean value of submitted DAP values

Head (soft tissue)

0.14

Taken to be the same as for head (skull and facial bones)

Neck (cervical spine)

0.28

Selected to yield the mean effective dose (mean of submitted
typical values) from the mean value of submitted DAP values

Neck (soft tissue)

0.28

Taken to be the same as for neck (cervical spine)

Chest-thorax

0.18

Table 4 in [U11] (for high kV)

Chest (thoracic spine)

0.19

Table 4 in [U11]

Chest (shoulder girdle
and ribs)

0.19

Taken to be the same as for chest (thoracic spine)

Mammography

No calculation, the reported value for mean effective dose wasused

Mammography(screening)No calculation, the reported value for mean effective dose wasused

Lumbar spine

0.21

Table 4 in [U11]Lumbo-sacral joint only

0.21

Taken to be the same as for lumbar spine

Abdomen

0.26

Table 4 in [U11]Pelvis and hips (bone)

0.29

Table 4 in [U11]Pelvis (soft tissue)

0.29

Taken to be the same as for pelvis and hips (bone)

Limbs and joints

0.16

Selected to yield the mean effective dose (mean of submitted
typical values) from the mean value of submitted DAP values

Whole spine (trunk)No calculation, the reported value for mean effective dose wasused

Skeletal survey (head andtrunk)

No calculation, the reported value for mean effective dose wasused

Dental intraoral

No calculation, the reported value for mean effective dose wasused

Dental panoramic

No calculation, the reported value for mean effective dose was
used

B28.
Table B7 shows that the highest typical effective doses are for whole spine (trunk), pelvis (softtissue) and lumbar spine, all of these more than 1 mSv; however, the values for the first two are basedon only 1–2 submitted values. Standard deviations are typically quite high, reflecting a high level ofvariability in doses between countries. Dental intraoral has with 0.006 mSv the lowest typical effective
dose per examination.

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

151

Table B7. Mean values of typical effective doses for projection radiography examinations reported to
UNSCEAR Global Survey
Examination type

Typical effective dose(mSv)

Standard
deviation

Number of countries
included

Head (skull and facial bones)

0.08

0.04

18

Head (soft tissue)

0.15

0

1

Neck (cervical spine)

0.13

0.08

23

Neck (soft tissue)

0.51

0.7

2

Chest-thorax

0.08

0.07

26

Chest (thoracic spine)

0.45

0.22

22

Chest (shoulder girdle and ribs)

0.06

0.05

6

Mammography

0.52

0.61

17

Mammography (screening)

0.66

0.72

10

Lumbar spine

1.01

0.60

25

Lumbo-sacral joint only

0.33

0.29

6

Abdomen

0.61

0.38

24

Pelvis and hips (bone)

0.49

0.19

25

Pelvis (soft tissue)

1.50

0

1

Limbs and joints

0.02

0.02

10

Whole spine (trunk)

1.55

0.07

2

Skeletal survey (head and trunk)

0.50

0

1

Dental intraoral

0.01

0.003

6

Dental panoramic

0.02

0.02

8

B29.
Table B8 summarizes the typical (mean) effective doses submitted to UNSCEAR Global
Survey for different radiography and fluoroscopy examinations, including both the effective doses
submitted and the values calculated from the DAP values by a conversion factor. The conversion
factors used in the calculation are shown in table B9. The DAP values when available with respective
conversion factors have been used to calculate the typical effective dose.

152

Table B8. Typical mean effective doses (mSv) for radiography and fluoroscopy examinations

Mean effective doses (mSv) per examination a,b
Gastrointestinal tract

7.9

3.2
2.5

3.8

15.4

4.2

2.3

4.9

0.5

9.2

4.1

9.1

1.6
0.4

18.4

8.6

9
8.2

0.1

9.8

Finland

15.9

3.2

4.4

France10.2

Germany

8

9

7

1.9

2.1

9

3

4

6.3

Greece

8.5

9

7

7

8.1

8.5

Iceland4.4

Lithuania

4.4

Malaysia

0.5

1.1
0.2
0.8

NorwayPolandPeripheral

Kidney, bladderand urethra

2.3

Czech Republic
Estonia

IVU

PelvicCholecystography

2.3

Belgium
Bulgaria

ERCP

Angiography
Abdominal

Cholangiography

Arthrography

Thoracic

Defecography

Myelography

Cardiac

Australia

Bariumstudy

Urogenital tract

CerebralCountry

Biliary tract

4.3
2.3

5.1

Republic of Korea

0.6

7.6

8.2

13.9

Romania

1.2

RussianFederation

3.2

Saudi Arabia

1.9

0.5

5.8
0.9

3.2
1.4

1.8

5.5
5.8

1.9

UNSCEAR 2020/2021 REPORTThe effective doses were calculated from reported DAP values, using conversion factors, or were directly reported values (in italics)
ERCP: Endoscopic retrograde cholangiopancreatography; IVU: Intravenous urography

Mean effective doses (mSv) per examination a,b
Gastrointestinal tract

IVU

Kidney, bladderand urethra

Slovenia

1.4

0.9

4.8

Spain

7

2

6.2

Sweden

1

0.6

2.5

Switzerland

4

2.2

10

United ArabEmirates

3.9

United Kingdom

1.4

0.06
4.2

1

PelvicCholecystography

Peripheral

ERCP

Angiography
Abdominal

Cholangiography

Arthrography

Thoracic

Defecography

Myelography

Cardiac

Bariumstudy

Urogenital tract

CerebralCountry

Biliary tract

0.3
1.1

Values are rounded; however extended precision has been preserved to illustrate differences.

b

Zero values are indicated when available; otherwise, cells have been kept empty.

0.1

6.5

5

4.6
ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

a

2.1

153

154

UNSCEAR 2020/2021 REPORT

Table B9. Conversion factors used for effective doses calculation from dose area product values forradiography and fluoroscopy examinations
DAP: Dose-area product; ERCP: Endoscopic retrograde cholangiopancreatography; IVU: Intravenous urography
Examination type

Conversion factor(mSv/(Gy cm2))

Selection of the conversion factor

Gastrointestinal tract(barium studies)

0.20

Table 4 [U11] (barium meal)

Gastrointestinal tract(defecography)

0.28

Chosen to yield the effective dose from DAP value
using their values submitted by Bulgaria

Biliary tract (cholangiography)

0.25

Chosen to yield the effective dose from DAP value
using their values submitted by Bulgaria

Biliary tract (ERCP)

0.26

Table 5 [U11]No calculation, the reported value for mean effective
dose was used

Biliary tract (cholecystography)
Urogenital tract (IVU)

0.18

Table 4 [U11]

Urogenital tract (kidney, bladderand urethra)

0.18

Table 5 [U11]No calculation, the reported value for mean effective
dose was used

Myelography
Arthrography

0.10

Table 5 [U11] (arthrograms)

Cerebral angiography

0.087

Table 5 [U11]

Cardiac angiography

0.20

Table 5 [U11]Thoracic angiography

No calculation, the reported value for mean effective
dose was used

Abdominal angiography

No calculation, the reported value for mean effective
dose was used

Pelvic angiography

No calculation, the reported value for mean effective
dose was used

Peripheral angiography
Lymphangiography

0.10

Table 5 [U11] (peripheral phlebography/venography)
No calculation possible, no DAP values submitted

B30.
Table B10 shows typical effective doses (mean values) for radiography and fluoroscopy
examinations. More details are also presented in electronic attachment B-1. The highest typicaleffective doses are for gastrointestinal tract (defecography), biliary tract (cholangiography, abdominal,
pelvic, cerebral and cardiac angiographies), all of these are more than 6 mSv. Urogenital tract (kidney,
bladder and urethra) examinations have the lowest typical effective dose, 1.3 mSv. For some types of
examinations, the mean value is based on only one or two submissions. As for projection radiography,
it should also be noted that the standard deviations are typically very high, reflecting large variations
between countries. For lymphangiography, no dose data have been submitted from any country, so it
has not been possible to present a mean value.

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

155

Table B10. Typical effective doses (mean values) for radiography and fluoroscopy examinations
ERCP: Endoscopic retrograde cholangiopancreatography; IVU: Intravenous urography
Examination type

Typical effective dose(mSv)

Standard
deviation

Number of countries
included

Gastrointestinal tract (barium studies)

3.4

2.8

15

Gastrointestinal tract (defecography)

8.8

8.3

3

Biliary tract (cholangiography)

8.5

5.9

5

Biliary tract (ERCP)

4.9

4.5

7

Biliary tract (cholecystography)

1.5

1.2

2

Urogenital tract (IVU)

2.4

2.2

13

Urogenital tract (kidney, bladder and urethra)

1.6

1.3

8

Myelography

5.5

5.2

2

Arthrography

2.1

2.8

2

Cerebral angiography

6.9

3.1

4

Cardiac angiography

7.0

3.4

18

Thoracic angiography

4.8

4.3

3

Abdominal angiography

8.0

1.4

2

Pelvic angiography

7.5

0.8

2

Peripheral angiography

3.2

1.4

3

B31.
Table B11 summarizes the typical (mean) effective doses submitted to UNSCEAR Global
Survey by countries for the different computed tomography examinations, including both the effective
doses directly submitted and the values calculated from the submitted DLP values by a conversion
factor. The conversion factors used in the calculation are shown in table B12. The typical effective dose
was calculated from the DLP with a conversion factor whenever the DLP had been submitted, i.e. also
in the case when both DLP and typical effective dose had been submitted. The mean value of typicaleffective doses for each type of computed tomography examination is shown in table B13 (see also
electronic attachment B-1).

156

Table B11a. Typical mean effective doses for computed tomography examinations

Mean effective doses (mSv) per examination a,bCT-head(skull and facialbones)

CT-head (softtissue andbrain)

CT-neck(cervical spine)

CT-neck (softtissue)CT-chest(thoracic spine)

CT-chest(thorax)

CT-abdomen(lumbar spine)CT-abdomen(abdomen)CT-abdomen(liver, pancreas,kidneys)Australia

1.4

1.5

3.6

2.5

6.7

4.8

8.1

8.1

11.1

Belarus1

Belgium

1.7

Brazil

2.7

2.8

4.7

Bulgaria

1.8

0.8

2.8

Czech Republic

1.9Country

Denmark
Estonia

0.6

Finland

6.3
2.3

3.7

7.9

7

8.9

13.9

11

4.3

5.8

5.8

0.7

5.2

6.6

9.1

1.8

7

2

2.2

13.4

0.9

7.2

1.4

France1.4

Germany

1.9

5.2

8.3
9.4

4.4
3.3

7.8

11

13.8

7.3

3.1

16

3.9

3.7

9.1

10.5

14

2

2.6

1.9

4.1

6.7

9.7

Lithuania

1.9

2.4

9.7

7.8

16.7

Luxembourg

1.8

4.3

7.1

6.7

10

13

9.6

Iceland

Malaysia

0.09

2.1

Norway

1.7

8.3

2.8

1.8

7.3
3

5.7

7

3.1

Greece

6.6

9.6

1.9

1.7

8.5

4.7

14

5.6

9.1

9.5

Philippines

1.1

1.4

3.9

3.9

14.3

10

17.1

31.4

Poland

1.8

3.6

2.9

4.6

8.7

10.1

8.9

22.3

Republic of
Korea

1.8

6.3

9.9

UNSCEAR 2020/2021 REPORTThe effective doses were calculated from reported DAP values, using conversion factors, or were directly reported values (in italics)
CT: Computed tomography

Mean effective doses (mSv) per examination a,bCountry

CT-head(skull and facialbones)

Romania

CT-head (softtissue andbrain)

CT-neck(cervical spine)

2.3

CT-chest(thoracic spine)

CT-chest(thorax)

CT-abdomen(lumbar spine)CT-abdomen(abdomen)

3.9

6.8

6.9

10.5

6.5

4.5

5.3

5.3

7.5

21

9.3

7.8

14.1

22.2

20.3

3

9.9

6.7

2.4

9.1

6.9

11.1

10.5

9.2

10.7

20.4

3.5

6.2

3.5

8.1

3.5

2.7

3.8

6

2.5

7

12

10.1

RussianFederation

1.7

4.1

2.4

Saudi Arabia

0.3

2.4

8.4

Slovenia

2.9

Spain

1.7

Sudan

2.4

Sweden

1.7

1.3

0.9

2.4

Switzerland

1.9

United ArabEmirates
United Kingdom

3.2

5

1.4
1.3

1.1
1.9

3.1

a

Values are rounded; however extended precision has been preserved to illustrate differences.

b

Zero values are indicated when available; otherwise, cells have been kept empty.

1.2

CT-abdomen(liver, pancreas,kidneys)

7.9

8.1
ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

TurkeyCT-neck (softtissue)157

158

The effective doses were calculated from reported DAP values, using conversion factors, or were directly reported values (in italics)
CBCT: Cone beam computed tomography; CT: Computed tomography
Country

Australia

Mean effective doses (mSv) per examination a,bCT-pelvis(pelvic bones)

CT-pelvis (pelvic soft
tissue and vascular)

6.1

6.3

CT-pelvis (pelvimetry)CT-full spine(neck, chest, abdomen)

CT-trunk (chest,
abdomen, pelvis)

16.7

11.3

CT-limbs

CT-dental

0.4

0.25

CBCTdental

BelarusBelgiumBrazil13.2

Bulgaria

11.2

Czech Republic

7.4

15
15.8

Denmark
Estonia

19.1
4.8

5.7

11.6

Finland

9.4
14.5

FranceGermany

5.3

Greece

7.7

Iceland

7.1

Lithuania

5.3

0.5
12.1

16.3

5.7

17.6

4.8

2

0.2

25.4

9.3

Luxembourg
Malaysia

8.2

Norway

19.8
7.3

5.6
25.8

Philippines

9.8

17.9

Poland

8.4

22.1

30.8

0.7
0.06

Republic of Korea
Romania

4.9

10.7

0.4

UNSCEAR 2020/2021 REPORT

Table B11b. Typical mean effective doses for computed tomography examinations

Country

Mean effective doses (mSv) per examination a,bCT-pelvis(pelvic bones)

Russian Federation

8.1

Saudi Arabia

14.6

Slovenia

9.8

Spain

11.6

CT-pelvis (pelvic soft
tissue and vascular)

CT-pelvis (pelvimetry)CT-trunk (chest,
abdomen, pelvis)

CT-limbs

CT-dental

CBCTdental

0.10
25.9

13

Sudan

0.5

0.49

0.06

10.1

SwedenSwitzerland

CT-full spine(neck, chest, abdomen)

9.7
8.1

8.1

Turkey4.4
8.7

United Kingdom

13.5

a

Values are rounded; however extended precision has been preserved to illustrate differences.

b

Zero values are indicated when available; otherwise, cells have been kept empty.

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

United Arab Emirates

159

160

UNSCEAR 2020/2021 REPORT

Table B12. Conversion factors used for effective dose calculations from dose length product values
for computed tomography examinations
CBCT: Cone beam computed tomography; CT: Computed tomography
Examination type

Conversion factor(mSv/(mGy cm))

Selection of the conversion factor

CT-head (skull and facial bones)

0.0021

Table 7 [U11] (Head)

CT-head (soft tissue and brain)

0.0021

Table 7 [U11] (Head)

CT-neck (cervical spine)

0.0059

Table 7 [U11] (Neck)

CT-neck (soft tissue)

0.0059

Table 7 [U11] (Neck)

CT-chest (thoracic spine)

0.014

Table 7 [U11] (Chest)

CT-chest (thorax)

0.014

Table 7 [U11] (Chest)

CT-abdomen (lumbar spine)

0.015

Table 7 [U11] (Abdomen and pelvis)

CT-abdomen (abdomen)

0.015

Table 7 [U11] (Abdomen and pelvis)

CT-abdomen(liver, pancreas, kidneys)

0.015

Table 7 [U11] (Abdomen and pelvis)

CT-pelvis (pelvic bones)

0.015

Table 7 [U11] (Pelvis)

CT-pelvis(pelvic soft tissue and vascular)

0.015

Table 7 [U11] (Pelvis)

CT-pelvis (pelvimetry)

0.015

Table 7 [U11] (Pelvis)

CT-full spine (neck, chest and abdomen)

0.015

Table 7 [U11] (Trunk)

CT-trunk (chest, abdomen and pelvis)

0.015

Table 7 [U11] (Trunk)

0.001

Selected based on the Romanian data so thatthe use of the conversion factor and thereported DAP value results in the reported
effective dose

0.0021

Selected based on the Spanish data so that theuse of the conversion factor and the reported
DAP value results in the reported effective
dose

0.002

Selected based on the Spanish data so that theuse of the conversion factor and the reported
DAP value results in the reported effectivedose

CT-limbs

CT-dental

CBCT-dental

CBCT-others

No calculation possible, no submitted dosevaluesB32.
It can be seen in table B13 that the highest typical mean effective doses are for computed
tomography examinations of trunk (chest, abdomen and pelvis) and full spine (neck, chest andabdomen), and for the two types of computed tomography examinations of abdomen, all of these are
more than 11 mSv. As could be expected, the dental computed tomography examinations have thelowest effective dose (0.3 mSv or less).

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

161

Table B13. Mean values of typical effective doses for computed tomography examinations
CBCT: Cone beam computed tomography; CT: Computed tomography
Typical effective dose(mSv)

Standard deviation

Number of countries
includedCT-head (skull and facial bones)

1.5

0.7

19

CT-head (soft tissue and brain)

1.9

0.8

23

CT-neck (cervical spine)

3.1

1.5

20

CT-neck (soft tissue)

2.8

1.2

11

CT-chest (thoracic spine)

8

3.2

16

CT-chest (thorax)

6.4

2.4

29

CT-abdomen (lumbar spine)

9.4

3.5

19

CT-abdomen (abdomen)

11.2

6.2

31

CT-abdomen (liver, pancreas, kidneys)

10.3

5.6

12

CT-pelvis (pelvic bones)

8.8

2.7

16

CT-pelvis (pelvic soft tissue and vascular)

10.9

6.1

12

CT-pelvis (pelvimetry)

5

4.8

3

CT-full spine (neck, chest, abdomen)

14.5

6.7

6

CT-trunk (chest, abdomen, pelvis)

16.7

6.9

13

CT-limbs

2.1

2.5

6

CT-dental

0.7

0.9

4

CBCT-dental

0.1

0.1

2

Examination

B. Literature review data
B33.
As for the results of the UNSCEAR Global Survey, only the typical (mean) effective doses
have been considered and not the typical (mean) values of dosimetric quantities. Typical effective doses
for a large number of types of procedures for all modalities using the TOP 20 methodology wasrecently reported by Vilar-Palop et al. [V6]. The study was based on a comprehensive literature review
from 2005 onwards through the Medline, Embase and Cochrane Library Plus databases, including
studies backed by scientific or governmental organizations. Twenty-seven articles and five webreferences were included in the study. Other variables included year and type of study (survey or
descriptive), country, method and sample used for the measurement. Mean effective dose, minimum,
maximum and standard deviation were calculated. Of these 20 procedures, a total of 378 dose values
were reported, 280 (74%) with calculations based on ICRP 60 [I9] and 98 (26%) based on ICRP 103[I11]. The results shown in table B14 were compared with data from the EC DDM 2 project [E5].

Category

Plain radiography

Fluoroscopy

Computed
tomography

Interventional radiologyaExamination

ICRP 60 [I9]ICRP 103 [I11]

Published E (mSv)

Mean E

Min-max E

Min-max E(mSv)

Standard
deviation

Mean E

(mSv)

(mSv)

(mSv)

Standard
deviation

Mettler et al.
[M10]

EC DDM 2 [E5]Chest/thorax

0.07

0.01–0.14

0.04

0.05

0.01–0.07

0.02

0.02

0.10

Cervical spine

0.08

0.02–0.18

0.06

0.05

0.01–0.11

0.05

0.20

0.19

Thoracic spine

0.60

0.23–1.22

0.43

0.50

0.10–1.20

0.40

1.00

0.64

Lumbar spine (incl. LSJ)

1.20

0.20–1.90

0.60

0.80

0.20–1.50

0.7

1.50

1.20

Mammography

0.33

0.26–0.46

0.11

0.64

0.40

0.27

Abdomen

0.92

0.21–2.10

0.60

0.50

0.14–0.75

0.25

0.70

0.90

Pelvis and hip

0.90

0.45–1.82

0.47

0.37

0.09–0.66

0.24

0.60

0.71

Barium meal

3.60

1.50–4.93

1.50

4.50

6.00

6.20

Barium enema

5.80

3.00–8.25

2.40

2.90

2.20–3.50

0.90

8.00

8.50

Barium follow-through

3.50

1.20–7.70

3.70

1.30

1.20–1.30

0.10

5.00

7.30

IVU

3.50

2.30–6.50

2.00

2.10

3.00

2.90

Cardiac angiography

9.30

3.30–22.30

6.40

3.10

7.00

7.70

Head

1.80

1.40–2.60

0.40

1.70

0.90–2.60

0.50

2.00

1.90

Neck

3.20

1.80–6.00

1.30

3.00

1.70–5.80

1.90

3.00

2.50

Chest

6.70

4.40–11.80

2.10

7.00

4.60–10.10

1.70

7.00

6.60

Spine

10.30

4.00–16.70

5.30

7.00

1.00–12.00

0.00

6.00

7.70

Abdomen

8.10

5.10–11.70

2.00

6.80

5.60–8.00

1.20

8.00

11.30

Pelvis8.30

4.00–11.90

2.40

7.40

5.70–9.90

2.20

6.00

7.30

Trunk

12.20

6.70–15.80

3.30

12.30

10.00–16.00

2.00

PTCA

19.50

7.40–48.60

15.10

7.20

Zero values are indicated when available; otherwise, cells have been kept empty.

14.80
15.00

15.20

UNSCEAR 2020/2021 REPORT

E: Effective dose; IVU: Intravenous urography; LSJ: Lumbosacral junction; PTCA: Percutaneous transluminal coronary angioplasty

162

Table B14. Comparison of mean effective dose for selected examinations according to different sets of ICRP tissue weighting factors (ICRP 60 [I9] and ICRP 103 [I11]),and published values [E5, M10]

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

163

B34.
The values of the effective doses calculated using ICRP 103 [I11] weights are lower than those
calculated using ICRP 60 [I9] weights for almost all procedures. The only exception is mammography,
and this is due to the increase in the weighting factor of the breast tissue (which has more than doubled,from 0.05 in ICRP 60 to 0.12 in ICRP 103).
B35.
Table B15 presents a comparison of mean effective doses of main paediatric examinations
with mean effective doses for adults conducted by Vilar-Palop et al. [V6]. Differences between
children’s age groups and adults vary greatly with examination types. For plain radiography
examinations in children, for some age groups it resulted in higher dose than those for adults. For
fluoroscopy procedures in children, the effective doses are consistently lower than those for adults. For
computed tomography examinations in children, effective doses for head, abdomen and pelvis are very
similar to those for adults, while those for chest and trunk are lower than those for adults.
Table B15. Description of mean effective doses for paediatric patients according to age group andcomparison with adult effective doses (according to ICRP 60) [V6]
IVU: Intravenous urography; LSJ: Lumbosacral junction
CategoryPlainradiography

Fluoroscopy

Computed
tomography

Examination

Effective dose (mSv) a,b<1 year

1–5 years

6–10 years

11–15 years

AdultsChest/thorax

0.05

0.05

0.05

0.06

0.07

Cervical spine

0.02

0.03

0.05

0.10

0.08

Thoracic spine

0.39

0.42

0.77

1.18

0.60

Lumbar spine(incl. LSJ)

0.4

0.5

0.6

0.8

1.2

Abdomen

0.07

0.09

0.15

0.27

0.9

Pelvis and hip

0.08

0.10

0.15

0.21

0.90

Barium meal

0.7

0.6

0.9

1

3.6

Barium enema

2.3

2.3

2.3

2.3

5.8

Barium followthrough

1.2

1.2

1.2

1.2

3.5

IVU

0.5

0.5

0.7

1

3.5

Head

1.7

1.6

1.8

1.6

1.8

Chest

3.9

2.8

4.2

6.8

6.7

Abdomen

7.9

7.9

8.1

Pelvis

7.9

7.9

8.3

Trunk

3.9

3

5.6

a

Values are rounded; however extended precision has been preserved to illustrate differences.

b

Zero values are indicated when available; otherwise, cells have been kept empty.

8.3

12.2

B36.
The differences between the mean effective dose values using ICRP 60 [I9] and ICRP 103[I11] tissue weighting factors, according to Vilar-Palop et al. [V6] are shown in table B16. In table B17,
corresponding differences are presented for paediatric computed tomography examinations [B26].

164

UNSCEAR 2020/2021 REPORT

Table B16. Comparison of mean effective doses calculated using tissue weighting factors from ICRP
60 [I9] and ICRP 103 [I11] for adult patients [V6]
E: Effective dose; LSJ: Lumbosacral junction; PTCA: Percutaneous transluminal coronary angioplasty
Mean E-60(mSv)

Mean E-103(mSv)

Ratio E-103/
E-60

Chest/thorax

0.07

0.05

0.71

Cervical spine

0.08

0.05

0.63

Thoracic spine

0.6

0.5

0.83

Lumbar spine (incl. LSJ)

1.2

0.8

0.67

Mammography

0.3

0.6

1.94

Abdomen

0.92

0.5

0.54

Pelvis and hip

0.9

0.4

0.41

Barium meal

3.6

4.5

1.25

Barium enema

5.8

2.9

0.50

Barium follow-through

3.5

1.3

0.37

Intravenous urography

3.5

2.1

0.60

Cardiac angiography

9.3

3.1

0.33

Head

1.8

1.7

0.94

Neck

3.2

3

0.94

Chest

6.7

7

1.04

Spine

10.3

7

0.68

Abdomen

8.1

6.8

0.84

Pelvis

8.3

7.4

0.89

Trunk

12.2

12.3

1.01

PTCA

19.5

7.2

0.37

Category

Plain radiography

Fluoroscopy

Computed tomography

Interventional radiology

Examination

Table B17. Comparison of mean effective dose calculated using tissue weighting factors from ICRP
60 [I9] and ICRP 103 [I11] for paediatric computed tomography examinations [B26]
Mean effective dose
E-60 (mSv)

Mean effective dose
E-103 (mSv)

Effective dose ratio
E-103/E-60

Brain

2

1.7

0.85

Chest

4

3.6

0.90

Abdomen/pelvis

5.1

3.9

0.76

Computed tomography
examination

B37.
Many recent population dose studies have made use of the data published in the EC DDM 1
project [E3]. This study was based on data from 10 European countries that reported mean typicaleffective doses in three levels (high, mean and low) following the TOP 20 methodology as presented intable B18. In the subsequent EC DDM 2 project [E5], mean values for the TOP 20 methodology basedon data from 36 European countries and also for the 10 earlier EC DDM 1 countries were reported.
These data are compared in table B19 with earlier estimated dose data for HCL I countries [U9].

Table B18. Comparison of mean effective dose between the European Commission Dose Data projects and UNSCEAR HCL I countries
HCL: Health-care level; IVU: Intravenous urography; LSJ: Lumbosacral junction; PTCA: Percutaneous transluminal coronary angioplasty
Modality
categoryPlainradiography

Computed
tomography

EC DDM 2 [E5]UNSCEAR HCL I
[U9]

Low

Mean

High

DDM 1 countries 10

DDM 2 countries 36

Effective
dose (mSv)

Effective
dose (mSv)

Effective
dose (mSv)

Mean effective dose(mSv)

Mean effective
dose (mSv)

Range

Max/min

Chest/thorax

0.01

0.10

0.25

0.1

0.1

0.014–0.25

18.6

0.1

Cervical spine

0.04

0.27

0.70

0.1

0.2

0.02–0.7

41.2

0.2

Thoracic spine

0.40

1.00

2.00

0.5

0.6

0.14–2.0

14.2

0.8

Lumbar spine (incl. LSJ)

0.50

1.90

2.80

1.3

1.2

0.29–3.15

10.9

2.2

Mammography

0.25

0.33

0.40

0.2

0.3

0.02–0.6

35.3

0.4

Abdomen

0.50

1.50

1.80

0.9

0.9

0.11–2.9

27.9

0.8

Pelvis and hip

0.45

0.90

1.35

0.6

0.7

0.21–2

9.7

1.1

Barium meal

2.60

7.70

15.00

7.2

6.2

0.8–15

18.8

Barium enema

6.40

8.60

12.50

8.1

8.5

2.2–25.2

11.5

Barium follow-through

4.40

10.00

24.50

5.7

7.2

0.63–24.5

38.9

IVU

2.60

4.00

3.50

2.9

2.9

0.43–5.63

13

2.6

Cardiac angiography

5.30

9.10

11.25

7.2

7.7

3.25–11.25

3.5

11.2

Head

1.60

2.00

2.40

1.7

1.9

0.28–3.98

14.3

2.4

Neck

2.40

2.50

2.80

2.8

2.5

0.42–5.38

13

Chest

6.60

8.00

8.20

5.5

6.6

2.03–20.4

10

7.8

Spine

3.60

5.30

6.00

8.3

7.7

2.38–16.3

6.9

5

Abdomen

10.20

12.00

13.50

10

11.3

2.61–28.7

11

12.4

Pelvis

8.70

8.70

8.80

6.3

7.3

0.8–14.5

18.1

9.4

Trunk

10.40

14.00

24.40

20.2

14.8

2.35–50.5

21.5

PTCA

13.15

14.00

17.00

12.9

15.2

4–29

7.3

Mean effective
dose (mSv)

7.4

11.9

165

Interventional
radiology

EC DDM 1 [E3]ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

Fluoroscopy

Examination

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UNSCEAR 2020/2021 REPORTB38.
The published mean effective dose values from the above studies are compared with theapplicable values obtained in UNSCEAR Global Survey in table B19 (projection radiography),table B20 (radiography and fluoroscopy) and table B21 (computed tomography).
Table B19. Comparison of mean effective doses for projection radiography
Data from literature and obtained from UNSCEAR Global Survey (both calculated and submitted values);
LSJ: Lumbosacral junction
Examination

Mean effective dose (mSv)
Current evaluation

E-60 [V6]E-103 [V6]EC DDM 2 [E5]Chest/thorax

0.09

0.07

0.05

0.10

Cervical spine

0.13

0.08

0.05

0.19

Thoracic spine

0.45

0.6

0.5

0.64

Lumbar spine (incl. LSJ)

1.04

1.2

0.8

1.20

Mammography

0.52

0.33

0.64

0.27

Abdomen

0.62

0.92

0.5

0.90

Pelvis and hip

0.49

0.9

0.37

0.71

Table B20. Comparison of mean effective doses (mSv) for radiography and fluoroscopy
Data from literature and obtained from UNSCEAR Global Survey (both calculated and submitted values)
Procedure

Mean effective dose (mSv)
Current evaluation

E-60 [V6]E-103 [V6]EC DDM 2 [E5]Barium meal

4

3.6

4.5

6.2

Intravenous urography

2.6

3.5

2.1

2.9

Cardiac angiography

7

9.3

8.1

7.7

Table B21. Comparison of the mean effective doses for computed tomography
Data from literature and obtained from UNSCEAR Global Survey (both calculated and submitted values)
Mean effective dose (mSv)

Computed tomography

examination

Current evaluation

E-60 [V6]E-103 [V6]EC DDM 2 [E5]

Head

1.7

1.8

1.7

1.9

Neck

2.9

3.2

3

2.5

Chest

7.2

6.7

7

6.6

Spine

14.5

10.3

7

7.7

Abdomen

10.7

8.1

6.8

11.3

Pelvis

8.4

8.3

7.4

7.3

Trunk

15.9

12.2

12.3

14.8

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

167

B39.
As computed tomography examinations on the average make the highest contribution to the
population dose, typical (mean) doses from such examinations deserve high attention. Some recent
studies dealing with the typical effective dose of computed tomography examinations are presented intables B22 to B26. Dougeni et al. [D7] reviewed published literature (after 2000) with the objective ofcollecting substantial information on effective dose during the most common computed tomography
examinations in adult and paediatric patients. This extensive review enables a thorough understandingof the range of effective doses possible in computed tomography examinations. The authors
demonstrated immense dose variations, up to 32-fold (table B23), indicating a large potential for dose
optimization. Tables B23 and B24 summarize the review by Dougeni et al. [D7].
Table B22. Ranges of effective dose for adult computed tomography examinations [D7]Computed tomography
examination

Effective dose (mSv)
Minimum

Maximum

Ratio (Max./Min.)

Head

0.4

7.9

19.8

Chest

1.9

26

13.7

Abdomen

2.4

55.2

23

Pelvis

1.9

36.5

19.2

Lumbar spine

0.8

11.6

14.5

Coronary angiography

1

31.8

31.8

Pulmonary angiography

1.4

19.9

14.2

Table B23. Ranges of effective doses for paediatric computed tomography examinations [D7]Computed tomography

examination

Effective dose (mSv) per age group

Number ofreferences<1 year1 year

5 years

10 years

15 years

Paediatric head

0.8–14.5

0.3–5.6

0.5–4

0.6–2.8

1–2.2

3–8

Paediatric chest

0.9–23.1

1–7

1.3–21.1

1.8–6.9

1.3–6.4

4–14

Paediatric abdomen

1.9–192.3–11.7

2.8–19.3

3.7–19.9

3.3–4.4

3–8

Paediatric abdomen-pelvis

13.1

8.5–19

3–10.4

4.4–14.4

3.1–16.1

1–2

Paediatric pelvis

1.5–8.4

6.7

6

6.4

4.7

1–2

Paediatric chestabdomen-pelvis

13

Paediatric angiography
Paediatric cystic fibrosis

1.3–17.2
1.5–4

1–28
1.5–29.3

1–2
2.6

3

1–3
1

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UNSCEAR 2020/2021 REPORT

Table B24. Mean effective dose values for adults computed tomography examinations [D7]Computed tomography
examination

Mean effective dose
(mSv)

Range

Number of references

Head

2

0.4–7.9

22

Chest

7.4

1.9–2621

High resolution

2.7

0.4–5.7

4

Abdomen

10.8

2.4–55.223

8.2–29.8

1

Thoracic spine
Cervical

2.2

0.3–4.1

4Pelvis8.5

1.9–36.5

12

Chest-abdomen-pelvis

11

8.1–16.6

2

Lumbar spine

6.2

0.8–11.6

10

0.6–31.8

23

Computed
tomography
coronary
angiography

Prospective

3.6

Retrospective

13.5

Calcium scoring

1.8

Pulmonary angiography

7.6

1.4–19.9

8

Appendix

4.6

4.5–13.3

3

Pancreas

8.4

5.1–14.6

2

Liver-spleen-pancreas

10.1

7.2–13

3

Kidneys9.4

7.9–11

2

B40.
A study by Shrimpton et al. [S14] presented the trend in the United Kingdom in effective doseof computed tomography examinations in three successive patient dose surveys (table B25). The levelsof DLP represent typical values for the United Kingdom, derived as mean values of the distributions ofmean doses (including tube-current modulation, where applied) from the computed tomography centres
participating in the national survey. The coefficients of E/DLP (mSv/(mGy cm)) for examinations on
adult patients were calculated as mean values over a range of computed tomography scanner models
operating at medium applied potentials (principally 120 kV). The values of E/DLP shown for paediatrichead examinations are based on those published previously by Deak et al. [D3] on the basis of E-103[I11] using a hermaphrodite mathematical phantoms.
B41.
Whereas the typical E for head examinations on children aged 0–1 year appears to have fallen
by over 10% between the two UK surveys (2003 and 2011), estimates for most examinations common
to both national reviews have increased in range from 20% (in relation to adult head) to over 400% (forhigh-resolution examinations of the chest). Such significant increases in E are explained in part byunderlying increases of 30–160% in the typical values of DLP, and partly from the application between
surveys of different sets of coefficients when estimating E from values of DLP.

Table B25. Typical effective dose (mSv) estimated for adult and paediatric patients undergoing common computed tomography examinations in the United Kingdom in2011 together with mean data from previous national surveys for 1989 and 2003 [S14]
DLP: dose-length product; E60: effective dose using ICRP 60 tissue weighting factors; E103: effective dose using ICRP 103 tissue weighting factors HE: effective dose equivalent
Examination

1989 a,b

2003 a,b

HE (mSv)

E60 (mSv)

E/DLP d,e
(mSv/(mGy cm))

DLP d,f(mGy cm)

E60 (mSv)

E/DLP d,g
(mSv/(mGy cm))

DLP d,f(mGy cm)

E103 (mSv)

Head

3.5

1.8

0.0021690

1.5

0.0020890

1.8

Cervical spine

1.9

2.9

(0.0059)

0.0057

525

3

Chest

9.1

8.3

0.014

400

5.8

0.027

500

14

0.014

88

1.2

0.027

230

6.2

Chest (high resolution) axial

0.027

110

3

Chest (high resolution) helical

0.027

360

9.7

Chest (high resolution) all(0.015)

0.024

800

19

CT- pulmonary angiography(0.015)

0.027

360

9.7

0.015

350

5.3

0.024

670

16

Abdomen and pelvis

0.015

470

7.1

0.020

645

13

Virtual colonoscopy(0.015)

0.020

780

16

Enteroclysis(0.015)

0.020

580

12

Kidney-ureters-bladder(0.015)

0.018

355

6.4

Urogenital tract(0.015)0.018

Paediatric
head

b
c
d
e
f
g

7.2

960

17

0–1 year

0.011

230

2.5

0.0069

h

315

2.2

>1–5 years

0.0040380

1.5

0.0044

h

530

2.5

>5 years

0.0032510

1.6

0.0027h750

2Effective doses refer to the hermaphrodite mathematic MIRD phantom; originally developed at Oak Ridge National Laboratory [C15].
Empty cell indicates no data available.
Effective doses for adults refer to average data for ICRP adult computational reference phantoms [I12].
Values for head and neck relate to measurements of DLP in a small (16 cm diameter) standard CT dosimetry phantom, whereas values for all other procedures relate to a large (32 cm diameter) phantom.
Values in parentheses reflect the general coefficients that would have been applied if these examinations had been included in the 2003 review.
Mean values from distributions of typical doses observed for sample in national survey.
Mean examination-specific coefficients for adult patients.
Values taken from Deak et al. [D3].

169

h

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ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

CT- angiography

Abdomena2011 b,c

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UNSCEAR 2020/2021 REPORTB42.
The typical effective dose of a computed tomography examination for a given anatomical
region can vary much depending on the indication of the examination. A study by Smith-Bindman et al.
[S17] indicated two–sevenfold differences and a study by Teeuwisse et al. [T2] three–sixfold
differences depending on the type of the computed tomography examination and indication. A few
more examples of published typical effective dose values for computed tomography examinations areshown in table B26.
Table B26. Examples of typical effective doses for diagnostic radiology examinations
CT: Computed tomography; CBCT: Cone beam CT; MSCT: Multi-slice CT
Examination

Effective dose(mSv)

Conversion factor used

2.7

0.014 mSv/(mGy·cm)

5.1

0.026 mSv/(mGy·cm)

9.6

0.026 mSv/(mGy·cm)a[C2]

CT by swallowing

3.9

0.0066 mSv/(mGy·cm)[K12]

C-arm flat panel CT

0.30±0.08

0.030–0.035 mSv/(mGy·cm)[B3]

Cardiac CT angiography

Head radiography (sinus and middle
ear)aReference

[S23]

0.02

Non-dental CBCT

0.09 to 0.10

MSCT for sinus

0.21 to 0.33

CBCT for middle ear

0.19 to 0.4

MSCT for middle ear

1.95 to 2.33

[D5]

Intraoral radiography

0.06–0.07 mSv/(Gy·cm2)

Panoramic radiography

0.08 mSv/(Gy·cm2)[H7]

ICRP 103 tissue weighting factors [I11].

V. DISTRIBUTIONS BY AGE AND SEX

A. UNSCEAR Global Survey data
B43.
To the UNSCEAR Global Survey, 11 countries submitted data on the distribution of
examination frequencies according to the age and sex of patients, mainly in five-year intervals
according to the survey template. In general, for population dose evaluations, also in most of the
published studies, paediatric examinations are almost always included in the total number of
examinations and not evaluated separately although the typical effective doses in paediatricexaminations can differ significantly.

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

171

B44.
The age distributions of examination frequencies for each modality are roughly similar among
different countries but the ratios of older to younger patients differ between countries. In particular, in
the Philippines, a significantly higher share of the projection radiography examinations is carried out
for younger patients than in other countries. In France, the percentage of young adults (about 20 to 40
years) in radiography and fluoroscopy examinations are significantly higher than in other countries. In
Brazil and Philippines, a higher percentage of computed tomography examinations seems to be in theyounger age groups (i.e. fewer computed tomography examinations of very old patients). Figures B-II
to B-IV summarize age distributions of examination frequencies from the UNSCEAR Global Survey.
B45.
The difference in the age distributions of frequencies between males and females is not verysignificant except for projection radiography, where a higher portion of examinations is performed forfemales aged between 40 and 70 years, mainly due to mammography examinations. For radiography
and fluoroscopy with contrast media, examinations of younger adults (<40–60 years) for females are
more numerous, while in the older age groups between about 50–80 years, examinations for males
outnumber those for females. Figures B-V and B-VI show that the ratio male/female is much higher in
Belgium than in Brazil. For computed tomography, the distributions between Brazil and Czech
Republic have roughly similar shapes although in Brazil the examinations for females over about
40 years seem to be more numerous, while the reverse is true for the Czech Republic (figure B-VII).
Further, the peak in Brazil is on lower age groups (around 60) than in Czech Republic (around 70).
B46.
The age and sex distributions of frequencies from the UNSCEAR Global Survey indicate
overall similar shapes of the distributions as in few published studies. However, the detailed data fromthis survey enabled up-to-date verification of typical distributions and the indications of differences.
Figure B-II. Percentage of examinations in each age group from total number of examinations inprojection radiography; for 10 countries reporting detailed data to UNSCEAR Global Survey

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UNSCEAR 2020/2021 REPORT

Figure B-III. Percentage of examinations in each age group from total number of examinations inradiography and fluoroscopy; for 10 countries reporting detailed data to UNSCEAR Global Survey

Figure B-IV. Percentage of examinations in each age group from total number of examinations incomputed tomography; for 11 countries submitting detailed data to UNSCEAR Global Survey

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

173

Figure B-V. Age and sex distribution for patients received projection radiography examinations in
Belgium and Brazil

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UNSCEAR 2020/2021 REPORT

Figure B-VI. Age and sex distribution for patients received radiography and fluoroscopy (withcontrast media) examinations in Belgium and Brazil

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

175

Figure B-VII. Age and sex distribution for patients received computed tomography examinations in
Brazil and Czech Republic

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UNSCEAR 2020/2021 REPORT

B. Literature review data
B47.
Data on frequencies and collective or per caput effective doses as a function of age and sex
have not been extensively published. In particular, published data on dose distributions and all
paediatric data are sparse. Therefore, the few reported examples are important for this evaluation eventhough these might not be representative for all cases.
B48.
In France, on average, the effective dose to women and men from diagnostic procedures using
ionizing radiation was similar, 1.3 mSv per year per caput in 2007 [E10] and 1.6 mSv in 2012 [D10](table B4), including all ages. In 2007, the distribution of effective dose according to age and sex
showed that the average effective dose per caput increased with age and was higher for men; theproportion of exposure due to conventional radiology and to computed tomography differed between
women and men (figure B-VIII). The effective dose due to computed tomography was much higher for
men aged over 55 due to a higher number of computed tomography examinations performed, especiallyabdominal and pelvic computed tomography, which contributed significantly to the collective dose.
B49.
A similar age distribution of frequencies was observed in France in the latest published surveyof 2012 [D10]. In 2012, about 44% of the French population had benefited from at least one diagnostic
examination using ionizing radiation. This percentage rose from 18% among children less than five
years to approximately 60% among adults aged around 70 years. Women were more likely to receive aradiological examination: 49% of the female population underwent at least one examination, whereas
only 39% of the male population did. A significant peak could also be observed for children andadolescents aged 10–19 years, who were roughly 10% more likely to undergo a radiologicalexamination than young adults aged 20–29 years.
Figure B-VIII. Distribution of average effective dose per caput from conventional radiology andcomputed tomography examinations by age and sex in France [E10]ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

177

B50.
A study in the Republic of Korea [L3] analysed national statistical data gathered during 2006–
2013 for seven types of radiography (general radiography, computed tomography, mammography,
fluoroscopy, angiography, dental and nuclear medicine; interventional procedures were excluded) forage groups classified by five-year intervals from 1 to 80 years (figure B-IX). The highest frequency of
examinations was in the 51–55-year age group for both males (10.8%) and females (9.2%) with adecreasing trend thereafter. The difference in frequencies between male and female patients aged over
41 years can partly be explained by the longer life expectancy of women.
Figure B-IX. Distribution of annual frequency of diagnostic medical examinations by age group andsex in the Republic of Korea in 2013 [L3]

B51.
Studies in France on radiation exposure from diagnostic medical procedures of the French
paediatric population are of particular interest, because of the general scarcity of paediatric data andbecause the French studies have been a very comprehensive and systematic effort. The first study from2010 paediatric data [E11] has recently been repeated for 2015 paediatric data [I20]. All diagnostic
imaging procedures using ionizing radiation (conventional radiology, dental radiology and diagnostic
interventional radiology, computed tomography and nuclear medicine), performed in 2015 on children
aged under 16 years at the time of the procedure, were considered.
B52.
The frequency of procedures for children according to the imaging modality and age group in2015 in France is shown in table B27. About 604 diagnostic procedures were carried out per 1,000
children aged under 16 years, which is relatively stable (+1.5%) compared to the value from 2010.
Children aged 11 to 15 years were the most frequently exposed, with 993 procedures per 1,000
children, whereas children aged 1 to 5 years were the least frequently exposed, with 250 procedures per
1,000 children. Conventional radiology and dental radiology accounted for 56 and 41%, respectively,
computed tomography for just over 2%, and nuclear medicine and diagnostic interventional radiology
for less than 1%. This distribution was substantially equivalent to the distribution in 2010. Girls were
exposed slightly more often than boys, for all age groups combined (+1.8%) [I20].

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UNSCEAR 2020/2021 REPORTB53.
The annual mean effective dose was 135 μSv per child, 25% less compared to that in 2010.
Conventional radiology contributed about 53% to this dose or 72 μSv per child, which was a 53 μSv
reduction compared with 2010. Computed tomography scans accounted for about 40% of the total doseor 55 μSv per child, which was a slight increase of 7 μSv since 2010. Dental radiology, nuclear
medicine and diagnostic interventional radiology together contributed less than 7% or 9 μSv, which was
a 2 μSv increase since 2010. The annual mean effective doses of girls and boys were identical.
Table B27. Number of diagnostic examinations per 1,000 paediatric patients according to imaging
modalities by sex and age in France [I20]
Modality category

Number of diagnostic examinations per 1 000 patients (%)<1 year

1–5 years

6–10 years

11–15 years

All ages

521 (95.8)

214 (85.5)

288 (48.9)

490 (49.3)

339 (56.2)

Boys

562 (95.1)

224 (85.2)

272 (48.4)

501 (51.6)

343 (57.6)

Girls

476 (96.8)

204 (85.9)

305 (49.5)

478 (47)336 (54.7)

0.5 (0.1)

26.7 (10.7)

289 (49.1)

478 (48.1)

249 (41.2)

Boys

0.3 (0.1)

28.8 (11)278 (49.6)

444 (45.7)

235 (39.6)

Girls

0.6 (0.1)

24.6 (10.4)

300 (48.6)

514 (50.5)

262 (42.8)

17 (3.2)

7.6 (3.1)

11 (1.8)

24 (2.4)

14 (2.3)

Boys

22 (3.7)

8.2 (3.1)

11 (1.9)25 (2.5)

15 (2.5)Girls

12 (2.5)7 (3)

11 (1.7)

23 (2.2)

13 (2.2)

3.4 (0.6)

1.7 (0.6)

0.8 (0.1)

1.8 (0.2)

1.5 (0.3)Boys

5.1 (0.9)

1.5 (0.6)

0.8 (0.1)

1.6 (0.2)

1.5 (0.3)Girls

1.6 (0.3)

1.9 (0.8)

0.9 (0.1)

1.9 (0.2)

1.6 (0.3)

1.5 (0.3)

0.2 (0.1)

0.1 (0)0.1 (0)0.2 (0)Boys

1.8 (0.3)

0.3 (0.1)

0.1 (0)0.1 (0)0.2 (0)Girls

1.3 (0.3)

0.1 (0)0.2 (0)0.2 (0)0.2 (0)543 (100)250 (100)

588 (100)

993 (100)

604 (100)Boys

592 (100)

262 (100)562 (100)

971 (100)

595 (100)Girls

492 (100)

238 (100)

616 (100)

1 017 (100)613 (100)

Conventional radiology

Dental radiology

Computed tomography

Nuclear medicine

Interventional radiology

All modality categories

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

179

VI. STAFF AND DEVICES
A. UNSCEAR Global Survey data
B54.
The numbers of various professionals per million of population submitted to the UNSCEAR
Global Survey are presented in table B28, and the numbers of various types of diagnostic radiology
systems and devices per million of population in tables B29 to B31.
B55.
The data on the numbers of professionals and diagnostic radiological systems and devices
generally show large variations between countries. From the total number of diagnostic systems, on
average, still more than half (about 56%) are analogue systems. The majority of computed tomographyscanners (not including computed tomography scanners used in nuclear medicine and radiation therapy)
are multi-slice scanners and, on average, less than 5% are single-slice scanners (excluding dental andcone-beam scanners).
Table B28. Number of professionals per million population working in diagnostic radiology reported
to UNSCEAR Global Survey
Number of professionals per million population aCountry
Australia

Radiologists

Dentists

71

874

Bangladesh

Otherphysicians b

Medicalphysicists

Radiationtechnologists

4.2

470

Nurses40

Belgium

136

24

166

4.5

Brazil47408

Bulgaria

122

1 088

Belarus125

571

Canada

69

592

Chile

58

1 198

Cyprus98

875

Czech Republic

136

708

Denmark

105

807

Estonia

154

955

163

8.4

Finland

114

802

54

9.1

France128

629

Germany81874

Greece313

1 269

Hungary102

611

Iceland

96

1 211

0.8

4

136

2.7

136

104

15

259

2.2

51

11

22

287

38

1.5

241

7.9

34

49

4.4
293

1.1

8.4
2 088

346

92

66

166

180

UNSCEAR 2020/2021 REPORT

Number of professionals per million population aCountry

Radiologists

Dentists

Iran (Islamic Republic of)

32

206

Italy

Other
physicians b

Medicalphysicists

Radiationtechnologists

Nurses

1 009

Japan

50

823

Lithuania

126

682

0

14

294

157

Luxembourg

109

862

140

7

421

349

Malaysia

7

221

Netherlands

535

North Macedonia

843

5.5

Norway

154

1 006

709

Poland

96

1 043

212

Republic of Korea

65

336

Romania

88

727

1.5

Russian Federation

111

250

1.9

218

San Marino

367

1 072

0

459

Saudi Arabia

258

417

551

106
98

674

439

Slovenia

100

656

2

244

Spain

95

668

5.6

187

Sweden

260

780

15

Switzerland

102

501

Thailand28

251

United Arab Emirates

306

557

United Kingdom

70

616

United States

85

606

310

259

31
550

3

380

4 751

0.7

27

2.4

20

710

27

96

375

13

240

35

10

UruguayaZero values are indicated when available; otherwise, cells have been kept empty.

b

Other physicians conducting radiological examinations.

Table B29. Number of diagnostic radiology systems per million population reported to UNSCEAR
Global Survey
Number of diagnostic radiology systems per million population a (% digital system)
Country

Total bRadiography

Argentina

295

167

Australia

951

113

Belgium

1 502

342

Bangladesh

38

Mammography

DentalAngiography

Densitometry

19

89

8.3

12

76

27

640

2.6

45

1 064

Fluoroscopy

3.1

21
16

31

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

Number of diagnostic radiology systems per million population a (% digital system)
Country

Total bRadiography

Fluoroscopy

Mammography

DentalAngiography

Densitometry

Brazil

388

110

7.2

27

230

4.1

11

Bulgaria

141 (16)92 (30)92 (27)28 (29)93 (55)8.7 (100)

6.4

Belarus193 (33)

30 (45)57 (19)5.3 (80)

38 (21)

3.5 (100)

0.9 (100)

Canada

1 777

Chile

115

China

45

35 (11)

Cyprus769 (10)117 (9)Czech Republic

1 016 (51)Denmark

1 424

1.3 (19)4.9

1

48 (11)42 (25)483 (0)7.4 (86)

38 (100)

110 (60)37

12 (81)653 (43)

12 (100)

9.7

1 387

967

78

17

1 171

4.4

18

Estonia

900 (74)109 (69)

11 (93)12 (88)661 (71)

8.4 (100)

7.6 (100)

Finland

1 385

172

5.3

30

1107

17

11

11 (100)

55 (100)

23 (100)

12

France35 (83)Germany

1 626

1 179

Greece

1 000 (10)Hungary

530

Iceland

1 383

157

Indonesia

32 (64)0

Iran (Islamic Republic)

77

58

Iraq

81

16

Italy

1 816

660

84 (4)

2.3 (8)59 (26)

428
61

15

1 115
22

7.6

Japan
Lithuania

699 (0)

2.6

630
734

131

35

15

565

8

7.6

1 422 (7)104 (53)

63 (8)

12 (100)

1 220

18 (100)

1.8 (100)

Malaysia92

73 (23)5.8 (14)7.6 (32)

5.1 (3.9)

5.1 (77)

3.7

Niger

4.4

Netherlands

129

Norway

928

70

78

15

662

18

10

Philippines

65 (43)32 (30)10 (40)4.4 (36)

5.6 (36)

0.4 (0)0.4 (0)Poland

515

91

28

15

345

9.8

8.1

Republic of Korea

564

564

187

63

662

Romania

231

59

36

12

109

4.6

10

Russian Federation250

148 (21)

14 (38)19 (29)38 (28)3.2 (100)

1.5 (100)

Saudi Arabia

142

San Marinoc

1 378

765 532

6 124

218 942919

919

96 151

Luxembourg

4.1

136

181

182

UNSCEAR 2020/2021 REPORT

Number of diagnostic radiology systems per million population a (% digital system)
Country

Total bRadiography

Fluoroscopy

Mammography

DentalAngiography

Densitometry

Slovenia395

78 (27)40 (83)19 (53)212 (62)

8.3 (65)

22

Spain

972

76

23

14

828

5.4

5.3

Sudan

19

Sweden

1 500

59

52

18

1 200

12

8.5

Switzerland

2 222

496

207

29 (100)

1 428

Thailand276

97 (66)28 (100)

6.9 (100)

124

3.6 (100)

3.5 (100)

United Arab Emirates

1 205

283 (77)

69 (81)40 (74)530 (84)

28 (63)34 (78)0.3 (60)

United Kingdoma24544 (20)

United States

2 058

52

25

47

1 757

8.9

36

Uruguay

217

71

21

23

175

6.4

2.3

Zero values are indicated when available; otherwise, cells have been kept empty.

b

Values as reported; may not equal sum of all categories.

c

Only digital systems.

Table B30. Image processing systems per million population reported to UNSCEAR Global Survey
Number of image processing systems per million population a
Chemical development
systems

Computed radiography digitalsystems

Total(Contribution ofdigital system (%))

Bulgaria

71

86

157 (55)

Belarus150

81

231 (35)

China

27

4.3

31.3 (14)Cyprus52553578 (10)

Czech Republic

188

237

425 (56)54

54 (100)

Country

Estonia
Luxembourg

0

14

14 (100)

Malaysia

17.7

0.5

18.2 (3)Philippines

0.2

0.2

0.4 (57)

Russian Federation

61

1.6

62.6 (2.5)

1 378

1 378 (100)San Marino
Slovenia

98

61

159 (38)

Spain

4.3

43

47.3 (91)

United Arab Emirates

5.3

95

103.3 (95)27

27 (100)

United StatesaZero values are indicated when available; otherwise, cells have been kept empty.

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

183

Table B31. Computed tomography scanners per million population reported to UNSCEAR Global
SurveyCT: Computed tomography (excluding scanners used in nuclear medicine or radiation therapy departments)
Scanners per million population aCountry

Total bArgentina

21.2

Australia

43.3

Bangladesh

2.8

Belgium

22.6

Brazil20.9

Bulgaria

32.7

Belarus

9.1

Canada

15.3

Chile

17.3

China

5.8

CyprusSingleslice CT

Multislice CT

Dualsource CT

DentalCT

Conebeam CT

0

22.6

2.1

17.3

2.9

0.6
0.7

32.1

0.1

8.2

0.8

0.24

12.2

3.8

33.6

0

30.5

0

0

3.2

Czech Republic

38.5

0

21.9

0.5

15.1

1

Denmark

23.3

23.3

17.5

1.2

Estonia

19.8

13.7

Finland

22.1

1.8

20.2

France

16.2

0

16.2

Germany

33.3

Greece

38.1

10.4

23.2

Hungary

12.2

Iceland

49.5

49.5

Indonesia

8.4

0

Iran (Islamic Republic of)

7

Iraq

6.2

Italy

33.2

Japan

103.2

Lithuania

21.8

0.7

20.4

1.4

0.4

25.6

Luxembourg

17.6

0

12.3

3.5

0

1.8

Malaysia

8.5

Niger

0.2

Netherlands

13.6

Norway

32.1

3.8

1.1

0.4
0.4

15.2
2

1.3

3.2

11.7

3.6

76.9

128.8

13

184

UNSCEAR 2020/2021 REPORTScanners per million population aCountry

Total bSingleslice CT

Multislice CT

Dualsource CT

DentalCT

Conebeam CT

171.8

0.3

Poland

18.7

Republic of Korea

37

Romania

15.4

0.8

12.8

1.1

0.7

Russian Federation

12.3

0.5

10.9

0

5.2

Saudi Arabia

9.5

San Marino

91.9

Slovenia

15.1

0

12.2

Spain

16.9

0

15.9

Sudan

1.1

1.1

Sweden21

23.5

Switzerland

38.7

Thailand

22.7

United Arab Emirates

25.6

United Kingdom

7.7

United States

41.9

Uruguay

17.4

30.6

61.2
2

3

6.8
1

0.1

17

1.5
57.3

0.5

10.9

0.2

9.5

2.1

7.8

0.4

1.7

0.9

14.5
0

41.9

a

Zero values are indicated when available; otherwise, cells have been kept empty.

b

Values as reported; may not equal sum of all categories.

B. Literature review data
B56.
A survey involving 93 countries on the global perspective of the medical physics workforce
performed for the International Organization for Medical Physics (IOMP) reported by Tsapaki et al.
[T9] a total of 29,179 medical physicists, of whom 8,702 were females (30%) and 20,477 males (70%).
The geographical distribution of medical physicists is presented in table B32, indicating a need formore medical physicists, especially in Latin America, the Caribbean and Africa.
Table B32. Global medical physicist workforce for various geographical regions compared topopulation size in 2017 [T9]
Geographical region

a

Total

Population a

Medical physicists per
million population

Africa697

1 287 920 518

0.5Asia (with Middle East)/Oceania

7 589

4 586 394 306

1.7

Europe10 062742 264 801

13.5

Latin America/Caribbean

1 256

652 012 001

1.9

North America

9 575

363 844 490

26.3World population in 2017 [W11].

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

185

B57.
The numbers of devices were surveyed in the EC DDM 2 project [E5]. The numbers ofcomputed tomography, mammography and angiography devices are shown in figure B-X.
Figure B-X. Number of specific imaging devices per million population in European countries [E5]Countries with no numbers did not reply to the questionnaire

B58.
The European Coordination Committee of the Radiological, Electromedical and Healthcare IT
Industry regularly published age and density data (number of systems in use per million population) ofcomputed tomography and angiography equipment (besides magnetic resonance imaging and molecular
positron emission tomography equipment). Figure B-XI shows the density profiles for computed
tomography systems in 2015 [C11]. The report also highlighted the dramatic deterioration in the age ofthe installed base of medical imaging systems, for example about 3,000 units, approximately a quarterof the computed tomography systems installed in Europe, were technically incompatible with radiation
dose-saving software upgrades [C11].

186

UNSCEAR 2020/2021 REPORT

Figure B-XI. Density of computed tomography equipment in Europe in 2015 (number of systems inuse per million population) [C11]VII. TRENDS
B59.
By 2009, the average annual per caput effective dose from medicine worldwide (about
0.6 mSv of the total 3.0 mSv was received from all sources) had approximately doubled in the previous
10–15 years [M10, U9]. Since then, in the countries involved in the UNSCEAR Global Survey andliterature review, the trend of increasing collective effective dose, or per caput effective dose, hascontinued on average while the increase is less notable than during the previous decade. The increase isdue mainly to continued increasing use of high dose procedures, particularly in computed tomography,
but also to some interventional radiology and nuclear medicine in some large countries (the UnitedStates in particular). For computed tomography, it has been shown that the observed rise in use cannot
be attributed primarily to the growth and ageing of the population [B17]. On the other hand, despite theincreased use of computed tomography, the increase of collective effective dose from computed
tomography has been slowed down in some cases due to the significant development of dose-saving
technology. At the same time, the frequencies and the per caput effective dose of some conventional
radiography or fluoroscopy procedures have been decreasing. For diagnostic radiology examinations,these general findings are supported by the results of the UNSCEAR Global Survey and several
published reports as shown below.

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

187

A. UNSCEAR Global Survey data
B60.
The frequencies per 1,000 population from the current survey have been compared with thedata from the UNSCEAR 2008 Report [U9] in tables B33 and B34, where the percentage changes
between the two data sets have been reported for all countries that submitted data to both UNSCEAR
surveys. The mean changes and the population-weighted mean changes are presented in the tables.
Similarly, the typical (mean) effective doses from the current survey have been compared with the datafrom the UNSCEAR 2008 Report [U9] in tables B35 and B36.
B61.
Table B33 indicates that, except for mammography, pelvis and dental examinations, thefrequencies of projection radiography examinations have decreased on average in the past decade. The
average decrease is most noticeable for head and neck, chest (thoracic spine) and lumbar spine
examinations. Except for coronary angiography, radiography and fluoroscopy examinations have also
decreased on average in the past decade. The average decrease is most remarkable for gastrointestinal
tract (barium studies) and biliary tract (cholecystography). Table B34 also shows that the frequencies ofcomputed tomography examinations on average have continued to increase in the past decade. The
overall effect is that the total frequency of examinations of diagnostic radiology and interventional
radiology has remained nearly the same, while the increase for dental examinations is around 100%.
B62.
Tables B35 and B36 suggest that the typical (mean) effective doses have generally decreased
during the past decade, although the notable increases in a few large countries (e.g., Australia, Belgium,
Germany, and the United Kingdom) for some projection radiography examinations, or the shortage ofdata in other cases (e.g., screening mammography, dental panoramic and computed tomography pelvis
examinations), results in increased average doses for some types of projection radiography andcomputed tomography examinations. For radiography and fluoroscopy examinations, a decrease intypical effective dose is more evident as the data for almost all countries showed a decreasing trend.
B63.
The data published in the UNSCEAR 2008 Report [U9] do not enable comparison of thecontributions of frequencies to the total frequency on a country level between the 2008 data and thepresent data. However, the summary data for HCL I can be compared as shown in table B37. While thiscomparison suffers from the non-equivalence of the countries included in both data sets, the results
highly suggest that the contributions of all radiography and fluoroscopy (without dental) to the total has
somewhat decreased while that of dental, computed tomography and interventional radiology
examinations, and also coronary angiography, have increased dramatically.

Projection radiography changes a (%)

AbdomenPelvis andhips (boneand soft
tissue)Limbs andjoints

−52

4.5

54

18

481

−72

−51

−13

−16

193

22

51

103

−8.7

106

−22

−48

Head
(skull, facialbones andsoft tissue)

Neck(cervical
spine)

Chestthorax

Chest(thoracic
spine)

Mammography

Mammography(screening)

Lumbarspine

Australia

−7

0.9

−36

−81

46

5

Belgium

−85

−83

−5

−77

0.5

Bulgaria

−1.8

91

69

−5.4

109

Czech Republic

26

56

114

970

−58

Finland

−71

−100

−17

−33

0.3

France−60

Germany−22

Greece−53

Iceland−69

Country

66
−44

−38
−48

−64

−6.1

18
238

−38

Japan

−53
6.2

78
−70

−30

Netherlands

−55

−21

33

94

1 139

98

84

106

227

−1

−18

−5.8

21

11

−11

51

5.8

−24
−35

−43

364

−5.2

−23

−55

−17

−40

11

25

35

32

31

128

121

−35

Romania

−45

18

95

28

397

Russian Federation

38

−24

154

−26

268

−32

−67

55

−43

−15

108

−40

−39

−85

Republic of Korea

Slovenia

1 770

−15

28

51

98

−96

−80

172

123

9 158

40

−28

NorwaySpain−38

Dentalpanoramic

208

Lithuania
Luxembourg

68

Dentalintraoral

2 253

−34

−35

0.9

0.5

−14

−28

180

139

175

34

229

54

13

511

−15

49

33

620

129

−56

−2.3

−67

14

97

126

148

−17

UNSCEAR 2020/2021 REPORT

Changes are expressed in percentage of frequencies per 1,000 population. Mean values and population-weighted mean values have been calculated for countries reported them; due tosome exceptionally high values, also median values have been calculated

188

Table B33. Comparison of frequency data for projection radiography examinations between UNSCEAR 2008 Report [U9] and UNSCEAR Global Survey for countries
reported to both evaluations

Projection radiography changes a (%)
Head(skull, facialbones andsoft tissue)

Neck(cervical
spine)

Chestthorax

Chest(thoracic
spine)

Mammography

Mammography(screening)

Lumbarspine

AbdomenPelvis andhips (boneand soft
tissue)Sweden

−94

−85

−68

−88

−42

139

−77

−74

−28

Switzerland

−85

−84

−39

−75

−38

−77

−27

0.6

United Kingdom

−89

−61

13

−33

65

78

−39

−26

Mean change (%)

−41

−24

17

19

77

274

−17

Population-weighted
mean change (%)

−20

−18

88

−12

166

1 015

Median change (%)

−56

−42

−17

−35

46

54

CountryaLimbs andjointsDentalintraoral

Dentalpanoramic

16

−7.9

238

46

20

44

56

105

973

6

150

41

246

102

55

−39

−14

11

−2

94

72

Empty cell indicates no data available.
ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION
189

190

Changes are expressed in percentage of frequency per 1,000 population. Mean values and population-weighted mean values have been calculated for countries reported them; due to some
exceptionally high values, also median values have been calculated
IVU: Intravenous urography
Radiography and fluoroscopy changes (%) aCountry

Bariumstudies

Australia

Computed tomography changes (%)aBiliary tract(cholecystography)

Urogenital tract(IVU, kidney,
bladder, urethra)

Cardiacangiography

143

−0.3

588
246

Belgium

−68

−76

−0.8

Bulgaria

−59

−77

−0.4

Czech Republic

−72

−0.7

−41

Finland

−60

−0.8

44

FranceGermany−76

Greece−95

Iceland

−46

−0.5

−0.7

Chest
(thorax, thoracic
spine)

Abdomen(lumbar spine,
abdomen, liver,pancreas, kidneys)

−60

−35

275

Total changes (%)aPelvis(pelvic bones,
pelvic soft
tissue andvascular)Without
dental

−30

−8.4

35

141

44

−69

93

124

−49

13

777

−2.3

−1.7

−54

5.2

45

−1.9

−11

−17

−25

159

44

23

37

33

48

−44

20

102

−97

−21

395

198

532

14
−87

Lithuania

−7.9
1 065

−68

66

−0.8

24

Netherlands
NorwayWithdental250

Japan

Luxembourg

Onlydental

148

199

72
−67

−0.8

Republic of Korea

106

82

950

883

Romania

−87

−0.9

66

−5.6

Russian Federation

−56

−0.8

1 392

1 696

784

99

7.3

17

10

13

−95

−27

−42

167

32

−2.1

904

26

49

116

55

378

UNSCEAR 2020/2021 REPORT

Table B34. Comparison of frequency data for radiography and fluoroscopy, computed tomography and total frequencies between UNSCEAR 2008 Report [U9] andUNSCEAR Global Survey for selected countries reported to both evaluations

Computed tomography changes (%)aRadiography and fluoroscopy changes (%) aCountry

Bariumstudies

Biliary tract(cholecystography)

Urogenital tract(IVU, kidney,
bladder, urethra)

Slovenia

Chest(thorax, thoracic
spine)

Abdomen(lumbar spine,
abdomen, liver,pancreas, kidneys)

322

−37

−41

102

147

Pelvis(pelvic bones,
pelvic soft
tissue andvascular)Without
dentalOnly
dentalWith
dental

103

172

−23

109

−7.5

131

215

101

−29

140

145

66

−59

−55

−73

4.7

61

Spain

−71

Sweden−84

Switzerland−78

United Kingdom

−73

−98

−0.9

−15

−0.9

−7.6

Mean change (%)

−73

−8

−0.7

202

246

181

167

18

197

−1

Population-weighted
mean change (%)

−124

−41

−0.7

104

195

338

87

22

96

17

Median change (%)

−72

−76

−0.8

55

130

92

99

1

109

−5

Empty cell indicates no data available.

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATIONa

Cardiacangiography

Total changes (%)a191

Projection radiography changes (%) aCountry

Australia

Head (skull andfacial bones andsoft tissue)

Neck(cervical
spine)

Chestthorax

Chest(thoracic
spine)

82

169

94

-40

Belgium

126

Bulgaria

33

Czech Republic-65

France18

Germany−25

Norway−63−62

Mammography

Mammography(screening)

Lumbarspine

AbdomenPelvis andhips (boneand soft
tissue)

300

68

−44

−38

414

−43

−37

−65

−87

Dentalintraoral

Dentalpanoramic

33

−90

−60

150

60

−70

−68

233

173

50

−40

100

−8.3

−20

−0.4

−39

−31

15

−21

−65

−8.2

Republic of Korea

76

Romania

−61

−50

−64

Russian Federation

−29

−38

25

Spain

−10

−65

−48

Sweden

a

Limbs
and
joints

−85

−20

−56

−84

16
−90

−50

33

−16

−11

−60

−32

−63

−24

−35

−28

−39

Switzerland

−80

−33

United Kingdom

157

73

Mean (%)

6.5

25

15

−37

−36

Population-weighted
mean (%)

29

42

45

−14

−30

Empty cell indicates no data available.

−86

−17

−54
−14

−81

4.7

−68

−39

−62

−50

−42

−28

61

6.7

90

27

−26

−28

−26

−60

150

42

14.8

−1.7

−26

−44

−58

150

UNSCEAR 2020/2021 REPORT

Changes are expressed as a percentage of the effective dose from the UNSCEAR 2008 Report [U9]192

Table B35. Comparison of typical mean effective doses (mSv) for selected main projection radiography examination between data from UNSCEAR 2008 Report [U9] andUNSCEAR Global Survey

Table B36. Comparison of typical (mean) effective doses for selected radiography and fluoroscopy examinations and for computed tomography examinations between
data from UNSCEAR 2008 Report [U9] and UNSCEAR Global Survey
Changes are expressed as a percentage of the effective dose from the UNSCEAR 2008 Report [U9]
IVU: Intravenous urography
Radiography and fluoroscopy changes (%) a

Abdomen (lumbar spine,
abdomen, liver, pancreas,kidneys)Australia

−51.8

−59.5

Belgium

−11.1

−37.9

−40.8

2.6

55.2

58.3

−5.2

1.4

26.4

100

−59.2

−25

Barium studies

Czech Republic

Cardiacangiography−43.4

FranceGermany

33.3

GreeceIceland−80.7

Norway−18.3

Republic of Korea
−84.3

Spain

−10.4

Sweden

−88.7

−77.8

Switzerland

−70.4

−58.5

United Kingdom-74.1

Mean (%)
Population-weighted mean (%)
Empty cell indicates no data available.

−13.2

−4.3

Romaniaa

Pelvis (pelvic bones, pelvic soft
tissue and vascular)

−86.7
3.9

23.5

60.4

−46.7

−37.9

−41.2

−65.

−42.1

3.5

−28.3

−12

20.3

−48.6

−52.6

−42.1

−18.7

−0.05

23.6

−24.3

−28

−27.5

−0.6

11.7

46.9

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

Chest (thorax,
thoracic spine)Country

Urogenital tract (IVU,
kidney, bladder andurethra)Computed tomography changes (%) a

193

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UNSCEAR 2020/2021 REPORT

Table B37. Comparison of frequency contributions between UNSCEAR Global Survey and UNSCEAR
2008 Report [U9]Data are HCL I and the world for selected imaging modalities; HCL: Health-care level
Modality category

Contribution to total frequencies (%)
UNSCEAR 2008 [U9]Difference

Current
evaluation

HCL I

World

HCL I

World

All radiography and fluoroscopy(without dental examinations)

62.5

74.3

80.7

−18.9

−29.1

Dental radiology

23.5

17

13.4

27.7

43

Computed tomography

13.1

8

6.3

39.1

52.1

Interventional radiology

0.9

0.2

0.1

76.6

88.3

Cardiac angiography

0.5

0.1

0.5

80.4

2.2

B. Literature review data
B64.
The EC DDM 2 project [E5] provided the possibility to compare trends in medical exposure inEurope because in the earlier EC DDM 1 project [E3], collective effective doses were also surveyed for
10 European countries. Table B38 compares the trend for frequencies for the TOP 20 methodology. It
can be seen that for several groups of plain radiography and fluoroscopy, the average frequency for
EC DDM 1 countries in 2015 [E5] is lower than the average for all 36 countries, while for coronary
angiography, PTCA and most computed tomography groups, the reverse is true. In the EC DDM 1
countries, the average frequencies for several groups of plain radiography and fluoroscopy havedecreased significantly from the results of an earlier study in 2008 [E3], while the frequencies for thecoronary angiography, PTCA and the computed tomography category have increased significantly, insome cases more than doubled (for CT trunk about threefold increase). Comparison of the results of the
EC DDM 2 project with the UNSCEAR 2008 Report [U9] shows that frequencies for mostconventional examinations in the survey are lower than in the UNSCEAR data for HCL I countries,
while the frequencies for some more complex examinations (e.g., coronary angiography and PTCA) arehigher. These differences reflect the fact that the UNSCEAR 2008 Report [U9] are global and generally
older than the data of the EC DDM 2 project.
B65.
Because the examinations with increased frequencies (coronary angiography, PTCA and all CT)
represent the high-dose procedures, the net effect is that the population dose seems to have increased in
the EC DDM 1 countries (table B39), where the corresponding trend in per caput effective dose ispresented. As only data from France, Germany, Switzerland and United Kingdom were based on complete
reported overall frequencies and data from other countries were based on a rough estimation (TOP 20
methodology), no strict conclusions about the trends can be drawn. However, there seems to be an upward
trend which could be anticipated from the increased frequencies, in particular for computed tomography
examinations, because the typical effective dose for these countries has not significantly decreased.

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195

Table B38. Comparison of averaged frequencies per 1,000 population obtained from EC DDM 2 [E5],EC DDM 1 [E3] projects and UNSCEAR 2008 Report [U9]
CT: Computed tomography; LSJ: Lumbosacral junction; PTCA Percutaneous transluminal coronary angioplasty
Frequency per 1 000 population a,b
Average 36
EC DDM 2
countries [E5]Average 10
EC DDM 1
countries [E5]Average 10
EC DDM 1
countries [E3]

Average UNSCEARHCL I countries[U9]

Chest/thorax

194

151

177

168

Cervical spine

26

17

26

32

Thoracic spine

17.5

9.8

15

16

Lumbar spine (incl. LSJ)

39.5

33.6

38.2

31

Mammography

63.3

69

58.2

43

Abdomen

22.5

18.4

21.4

45

Pelvis and hip

48.7

59.4

59.3

40

Barium meal

3.8

1.5

3.6

Barium enema

2.6

1.6

4.7

Barium follow-through

1.2

0.7

1.1

Intravenous urography

2.8

2.3

7

8.5

Coronary angiography

4.2

5.6

5.4

1.5

CT-head

26.9

31.9

26.3

40

CT-neck

3.9

6.2

2.9

CT-chest

12.6

17.3

8.9

24

CT-spine

8.4

12.7

10.5

11

CT-abdomen

18.1

28.9

14.4

30

CT-pelvis

4.1

4.8

3.5

19

CT-trunk

9

5.3

1.8

PTCA

2

2.8

1.2

Examinationa

Values are rounded; however extended precision has been preserved to illustrate differences.

b

Empty cell indicates no data available.

9.3

0.9

B66.
Besides the EC DDM 1 and EC DDM 2 projects, data on trends in frequencies/population
doses have been reported separately by several other countries. In Finland, by 2008, the collective
effective dose from X-ray examinations had remained stable over the past decade [B19]. About 50% of
the collective effective dose from X-ray examinations was caused by computed tomography in 2005 (in1997 only 20%) and in 2008 it increased to 58%. In the fluoroscopy category, the barium meal
examination was a rare procedure and only the barium swallow examination from the suggested
TOP 20 procedures is among the most frequent contrast enhanced radiography procedures in Finland.
Instead, more frequent procedures were contrast enhanced fluoroscopy of biliary and pancreatic ducts.
However, their contribution to the total TOP 20 collective effective dose is only 1%. The onlyinterventional procedure among the TOP 20 procedures is PTCA while in Finland other procedures,such as nerve root block, have made a remarkable contribution to the dose.

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Table B39. Comparison of overall effective doses per caput from EC DDM 1 [E3] and EC DDM 2 [E5]Values presented for the 10 countries that participated in both projects
Country

Effective doses per caput (mSv)
EC DDM 1 [E3]EC DDM 2 [E5]Ratio EC DDM 2 / EC DDM 1

Belgium

1.77

1.96

1.11

Denmark

0.46

0.89

1.92

France

0.70

1.25

1.78

Germany

1.66

1.67

1.01

Luxembourg

1.82

1.79

0.98

Netherlands

0.45

0.63

1.39

Norway

1.10

1.25

1.14

Sweden

0.68

0.77

1.14

Switzerland

1.00

1.18

1.18

United Kingdom

0.38

0.39

1.04

Mean

1.00

1.18

1.27

B67.
In France, the average number of diagnostic examinations using ionizing radiation wasconstant between 2002 and 2007 and equal to 1.2 examinations per year per person [E10]. The use of
conventional radiology decreased over that period (0.77 examination per year per person in 2002 versus
0.74 in 2007) while use of computed tomography increased (0.10 examination per year per person
versus 0.12) as did the use of nuclear medicine (0.013 examination per year per person versus 0.018).
Computed tomography was used more in 2007, and a higher percentage of computed tomography wasfor chest (21% in 2007 versus 12% in 2002) and abdomen-pelvic computed tomography (31% versus
18%) while frequency of head and neck computed tomography decreased (28% versus 37%). This trend
led to a significant increase in average effective dose per person between 2002 and 2007: 0.83 mSv per
year per person in 2002 to 1.3 mSv per year per person in 2007. This change represents an increment of
57% of the total dose of ionizing radiation delivered to the French population for medical diagnostic
purposes. The latest published survey from France [D10] indicated an increase of almost 4% over a
decade for all modalities together. This was mainly due to a major rise in dental radiology (40% overthe same period) and to a lesser extent to computed tomography (34%). The average individual
effective dose increased by 20% between 2007 and 2012, from 1.3 mSv to 1.6 mSv. This increase ismuch less noteworthy than that of the previous period (57% between 2002 and 2007) and can be mostly
explained by an increase of 10% in the number of computed tomography examinations per person
between 2007 and 2012; and by a better knowledge of clinical practices and delivered doses,
particularly for computed tomography.
B68.
In France, a recent study on paediatric medical exposure [I20] indicated very few changes in
the frequency of diagnostic procedures in 2015 compared to 2010. The annual mean effective dose,
calculated for the whole population as for the exposed population, was significantly lower than in theprevious study. The fact that this reduction in children’s mean exposure was observed, even though thenumber of imaging procedures was stable, indicates that the reduction is linked to the decrease in themean effective dose per procedure. Several explanations related to better techniques and practices could
be associated with this reduction too, such as the use of digital image receptors in conventional
radiology and iterative reconstruction algorithms in computed tomography, improved awareness of

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197

optimization and justification among professionals, increased involvement of medical physicists inradiology and the use of best practice guidelines as requested by European regulations [E4].
B69.
In Germany, almost constantly, 1.7 X-ray procedures per person and year were performed in
2007–2014. The frequency of most conventional X-ray examinations decreased during this period (e.g.,radiographies of head by 15%, of thorax and spine by 20%, and X-ray examinations of digestive andurogenital tracts by 30%). On the other hand, dental X-ray examinations increased from 0.6 to 0.7 perperson. The frequency of computed tomography examinations increased by about 40% from 2007 to
2014. In 2007, computed tomography contributed 6% to frequency and 56% to collective effective
dose, while in 2014, the contributions were 8 and 64%, respectively. The doses per computed
tomography procedure were only slightly reduced despite various dose reduction approaches
established in preceding years. Therefore, the rising computed tomography frequency caused anincrease in the total mean dose per person by about 15% between 2007 and 2014 [N3].
B70.
In the Netherlands, besides analysing the trends in per caput effective dose, the trends in
population statistics are compared to the trend in the number of computed tomography scans for theperiod 2001–2011 [B17]. The increase of per caput effective dose is mainly due to both radiology andcomputed tomography examinations. In 2011, computed tomography with 0.45 mSv and diagnostic
radiology with 0.40 mSv made both together 89% of the per caput effective dose (0.95 mSv) [B17].
Further, the collective dose from medical exposure increased by 30% between 2001 and 2011.
Routinely collected data on computed tomography examinations in the Netherlands [R8] have beencombined with population size and age information available from Statistics Netherlands to show thatthe observed rise in the use of computed tomography cannot be primarily attributed to the growth andageing of the Dutch population (figure B-XII). This is a key finding, because population ageing is often
assumed to be one of the driving forces behind the increasing (collective) medical radiation exposure.
Plausible explanations for the increasing use of computed tomography may include its increased
availability and associated technology push, its expanding technical capabilities (e.g., for cardiac
imaging), and changes in the attitude of both medical staff and patients towards the deployment ofcomputed tomography for imaging. The latter may involve computed tomography educated medical
staff becoming more prone to perform scans, fear of litigation among medical staff leading toprecautionary computed tomography.
B71.
In Switzerland, a survey showed that the annual effective dose of 1.2 mSv per caput in 2008
increased by 0.2 mSv from its 1998 value [S3]. The frequency of computed tomography examinations
continued to increase from 2008 to 2013, leading to a 17% increase in the average annual effective dose
per person [L2].
B72.
In the United States from 1950 to 2006, the frequency of diagnostic radiological examinations
increased almost tenfold [M10] but since then by 2016 the value remained essentially the same eventhough the population had increased by about 24 million. Using the ICRP Publication 60 [I9] tissue
weighting factors, the annual per caput effective dose from diagnostic and interventional medical
procedures was estimated to have been 2.9 mSv in 2006 and 2.3 mSv in 2016 [M11, N2]. The largest
contributions to the per caput effective dose came primarily from computed tomography and nuclear
medicine [M9, M11, N1, N2].

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Figure B-XII. Observed and estimated trends in numbers of computed tomography examinations for
Dutch population
Estimated trend follows from number of examinations in 2001, change in population size, and change in age
distribution of population [B17]

B73.
In Australia, trend analysis (1999–2004–2010) indicated increasing trend of per caput effective
dose, mainly caused by an increase in computed tomography examinations by about 7.2% per year
[H6]. Trends in the collective effective dose were not directly proportional to frequency and so cannot
be estimated on the basis of frequency alone. Studies on the trends of paediatric computed tomography
in Australia [B27, B28] have shown significant increase in paediatric computed tomography imaging
frequency (average annual increase of 5.1%) until about 2000. Since then, the increase in paediatriccomputed tomography frequency has slowed overall or in some cases even declined.
B74.
In Taiwan, China from 2000 to 2013, the average annual growth rate of computed tomography
examinations was 7.6% [Y1]. The number of computed tomography examinations in 2013 was
2.6 times that in 2000. The population effective dose was 0.30 mSv per caput in 2000 and increased to
0.74 mSv per caput in 2013, with an annual growth rate of 7.2%.
B75.
In Kenya, the total number of examinations and the collective effective dose are increasing
annually, indicating a significant change in the medical imaging pattern, where new types of procedures
are conducted using high dose imaging modalities [K13]. The annual number of X-ray examinations per
1,000 population was estimated to be 82. This per caput estimate is 156% larger than that for 1986
(32 examinations per 1,000 population). There was a strong indication that access to diagnostic
radiological services in Kenya would continue to increase. The national annual number of computed

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199

tomography examinations increased by 60% from 2007 to 2011, which demonstrated the impact ofmulti-slice or multi-detector scanners (MSCT) since it was introduced in the country.
B76.
In the Republic of Korea, the number of diagnostic radiological devices increased by 22%
from 2008 to 2012 [L3]. From 2006 to 2013, the frequency of examinations demonstrated a rapid
growth of 54.4% (average 6.5% per year), while annual collective effective dose and annual per caput
effective dose increased from 0.89 mSv per caput effective dose in 2006 to 1.54 mSv in 2013 [L3].
B77.
In the Russian Federation, the collective effective dose from medical exposure has decreased
by a factor of two since the end of 1990 and has stabilized in 2015 at a level of about 77,000 man Sv(0.52 mSv per caput). This process is accompanied by an increase in the number of examinations –about 35% in the past decade. A decrease in the collective effective dose by 4% per year on average
was mainly due to the replacement of analogue X-ray units by digital units and a reduction of thenumber of high-dose fluoroscopies [B6]. The numbers of computed tomography units and examinationsin the Russian Federation doubled between 2010 and 2015, reaching 8.5 million examinations.
However, it still represented only 2.9% of the total number of diagnostic examinations and 44.9% in thecollective effective dose in the country. The trends of contributions of different imaging modalities in
the collective dose in the Russian Federation are shown in figure B-XIII.
Figure B-XIII. Contribution of various types of imaging modalities to collective dose from medical
exposure in the Russian Federation between 1999 and 2015 [B6]B78.
As for international trends in paediatric computed tomography examinations, a large
epidemiological study, “Epidemiological study to quantify risks for paediatric computerized
tomography and to optimise doses” (EPI-CT) [I6], investigated the relationship between the exposure toionizing radiation from computed tomography scans in childhood and adolescence and possibly
attributable late health effects. While the study did not provide information on population doses, theknowledge gained on current and past paediatric computed tomography examination practice will help
to propose strategies for further dose reduction.

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1.

Impact of technology

B79.
The development of imaging technology plays an important role in the trends of imaging
practices, numbers of examinations and patient dose levels. Development means the introduction of
new imaging technologies by manufacturers, including improved detectors and imaging principles, andassociated equipment and software. There is an extensive variation in the availability of newtechnologies worldwide and, in many low-income and very low-income countries, the level oftechnology is still largely non-digital, based on older techniques and often lacking appropriate
provisions for patient dose monitoring (such as DAP meters) [R5]. There are also variations in theselection of the imaging modality for a given clinical investigation, or in the types of equipment
available within a chosen modality (different manufacturers or different models of the same
manufacturer). While trends in imaging practices and patient dose levels are affected by the availabilityof new technologies and by the variations of modalities and equipment, these will not be considered
here.
B80.
During the past decade, major technological developments in computed tomography have been
impacting population dose from medical exposure. This is because in many countries, at least in highincome countries, computed tomography makes the highest, up to 70–80%, contribution to thecollective effective dose from all medical X-ray procedures. On the other hand, the major changes inthe development of X-ray examinations, such as the replacement of the conventional film-screen
systems by digital techniques, the replacement of computed radiography techniques by direct digitaltechniques, and the development of new detectors with higher detective quantum efficiency, have been
introduced and largely implemented already during the preceding periods and thus discussed inprevious UNSCEAR reports [U6, U9]. Therefore, the discussion below is limited to conventional andcardiac applications of computed tomography.
B81.
While there is no doubt about the impact of technology development in several cases, a recent
extensive study on computed tomography examinations indicated that the high variations of patient
doses across countries are primarily attributable to local choices regarding technical parameters, rather
than patient, institution or machine characteristics [S19].

(a) “Conventional” computed tomography
B82.
In computed tomography, the development of technology during the past 10–15 years has had
a pronounced effect both on the number of computed tomography examinations and on patient doselevels. The single-slice (or single-detector) scanners have been largely replaced by computed
tomography scanners with a marked increase in the number of detector rows, i.e., multi-slice or MSCT.
The improved efficiency of modern MSCT scanners has contributed to the increase in the number ofcomputed tomography examinations while also broadening the use of new computed tomography
applications. As a few examples, a pronounced increase of the number of computed tomography
examinations after 2000 was reported to coincide with the introduction of MSCT in Denmark [H2] andthe United States [M9]. Faster computed tomography scanners have increased the use of computed
tomography for paediatric examinations by reducing the requirement of sedation to prevent children
from moving during examination and by enabling less need for oral contrast administration, reduced
amount of intravenous contrast medium, and improved image quality [D8]. Computed tomography
technology has developed strongly towards better dose management with significant reduction ofpatient doses, by introduction of automated tube current modulation and iterative image reconstruction.

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

201

B83.
Effective doses (E, mSv) were assessed in several countries with regard to the publication year
and scanner technology (i.e. single-slice versus multi-slice) [P4]. Among studies, the considerable
variation in reported values was attributed to variations in both examination protocol and scannerdesign. The effective doses of computed tomography examinations for head, chest and abdomen prior
to 1995 were significantly higher than for later studies whereas between 1996 and 2009, effective dose
remained virtually unchanged [P4]. Significant dose reduction in more recent studies was attributed tothe implementation of dose management procedures, X-ray beam filtration and collimation, tube
current modulation and adaptation for patient body habitus, peak kilovoltage optimization, improved
detection system efficiency, and noise reduction algorithms [P4].
B84.
In a study by Chen and Moir [C5], average effective dose per computed tomography
examination in Canada from MSCT scans was shown to be 13–36% higher than from single-slice
scans. A study by Kim et al. [K8] showed differences in effective dose and organ dose between singleslice and multi-slice scans with a ratio of effective doses of 2.4 higher doses from MSCT for highresolution lung scan, 1.1 for head scan and 2.2 for abdomen scan. However, for chest scans theeffective dose using MSCT was 20% lower due to the application of dose-saving techniques.
B85.
While the MSCT technology of early 2010s has led to increasing patient doses compared withearlier technologies of late 1990s, the associated development of dose-saving features, such as iterative
reconstruction, has converted this dose trend downwards for most types of computed tomography
examinations. Studies and reviews on radiation exposure from computed tomography indicated apotential for dose reduction by applying innovative dose-saving techniques in combination with
optimized protocols [K1, M3, N6].
B86.
According to a study by Schegerer et al. [S8], the data provided for about 11% of all computed
tomography scanners operated in Germany in the years 2013 and 2014, the effective dose was 4.6/5.9
mSv per examination. The CTDIvol values, and consequently the effective doses, were considerably
reduced by about 15% compared with computed tomography practice before 2010. Modern computed
tomography technology, such as tube current modulation and iterative reconstruction reduced theeffective dose considerably by 6 and 13%, respectively. Considering examinations where iterative
reconstruction was not used, tube current modulation reduced CTDIvol and effective dose considerably
by 7 and 6%, respectively, and a marked dose reduction up to 35% was obtained for someexaminations. When using iterative reconstruction, CTDIvol and effective dose were considerably
reduced by 15 and 13%, respectively, compared with scans reconstructed with the conventional filtered
back projection algorithm. In the German study, the mean effective dose for scanners produced bydifferent manufacturers differed by 25% at maximum. These differences may be due to technicaldifferences (e.g., filtering, detector efficiency, the amount of tissue irradiated without being
reconstructed (over ranging), effectiveness of dose-saving measures) or to differences in optimization
protocols [S8].
A specific development within the computed tomography technology has been the introduction
B87.
of dual-energy computed tomography, which can also have an impact on patient dose levels. For thecomputed tomography examinations of adults there is phantom and clinical evidence that this technique
is not associated with increased radiation dose to patient [H9]. For paediatric computed tomography
examinations, the use of dual-energy computed tomography resulted in radiation doses comparable toor even less than that from single-energy computed tomography scans while maintaining contrast andcontrast-to-noise ratio [S15].

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UNSCEAR 2020/2021 REPORT

B88.
Besides the number of computed tomography examinations and patient dose, the developmentof computed tomography technology had an impact on the pattern of computed tomography procedures.
As for the imaged anatomical regions, a trend towards an increasing proportional contribution of
abdomen/pelvis and chest scans with a simultaneous decrease of head scans over time has been
observed [D8, E10, M8, M10, S7]. Although differences in living conditions and population
distributions may result in different computed tomography patterns worldwide, the increasing
proportions of abdomen/pelvis and chest scans may have resulted from the introduction of faster andmore efficient computed tomography scanners [F5].

(b) Cardiac computed tomography
B89.
In cardiac radiology, the development of computed tomography scanning technology has
progressed with significant dose savings. A review by Efstathopoulos et al. [E6] reported patient
effective doses associated with coronary artery calcium scoring (20 studies) and computed tomography
coronary angiography (61 studies). Patient effective doses from computed tomography cardiac
examinations varied among institutions due to examination protocol and computed tomography scannertype variations. The conventional retrospectively electrocardiogram (ECG) -gated helical scan protocol
does not use radiation as efficiently as the prospectively ECG-triggered scan techniques. Publishedresults indicate that the use of prospective ECG triggering is more effective in minimizing patient
exposure compared with dose modulated retrospective ECG gating.
B90.
Prospective acquisition was shown to allow for major dose savings compared to retrospective
acquisition (mean effective dose 4.5 mSv with prospective acquisition versus 27.5 mSv withretrospective acquisition) [B12], and mean effective dose 6.0 mSv for prospective computed
tomography angiography (CTA) and 8.4 mSv for retrospective computed tomography angiography[O4]. In a recent German study [S8], the dose was significantly reduced by 55% with prospective
triggering compared to retrospectively gated computed tomography coronary angiographies (CTCA).
Further evidence of the benefits of prospective acquisition techniques is provided by a recent large
international study by Stocker et al. [S23] in which 61 hospitals from 32 countries prospectively
enrolled 4,502 patients undergoing cardiac CTA during one calendar month in 2017 were analysed. The
median DLP of coronary CTA was 195 mGy cm (range 110–338 mGy cm), corresponding to effective
doses of 2.7 or 5.1 mSv, estimated using the thoracic or the recently published cardiac DLP to effective
dose conversion factor of 0.014 or 0.026 mSv/(mGy cm), respectively. The authors compared theresults with a similar survey conducted in 2007. A significant 78% reduction in DLP for CTA wasobserved in 2017 (P < 0.001), without an increase of frequency in non-diagnostic coronary CTAs (1.7%
in 2007 versus 1.9% in 2017 surveys, P= 0.55). Among the major factors contributing to this dose
reduction is the availability of dose efficient scan protocols with a reduced tube potential, prospective
ECG-triggering and iterative image reconstruction. However, a large 37-fold inter-site variability inmedian radiation dose was observed, which underlines the need for further site-specific training andadaptation of contemporary cardiac scan protocols. In a recent study by Alhailiy et al. [A3], diagnostic
reference levels for CTCA in Australia were established and shown to be lower than in most publishedstudies, due to the implementation of dose-savings technologies such as prospective ECG-gated mode
and iterative reconstruction algorithms.

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203

VIII. SUMMARY
B91.
The current UNSCEAR Global Survey, with data contributed by over 50 countries, together
with a comprehensive review of the literature published in the past decade, has amassed key data on
frequency and dose for diagnostic radiological examinations. This includes information on the age andsex distributions of patients, professional staffing levels, and numbers of imaging devices. For theevaluation of collective effective doses or per caput effective doses, the findings are based mainly on
the literature review since the survey participation has not been sufficient for direct and accurate
estimations of the population dose from medical exposure. A general observation is that the countries
that have published information on medical exposure in the past years are mainly the same countries
that have submitted data to this survey. It seems that these countries have established mechanisms
enabling them to collect information on the frequency of radiological examinations, to record dose data
and to provide updates on a regular basis.
B92.
Frequencies of diagnostic radiology examinations per 1,000 population vary considerably
between countries, according to data in the literature and in the UNSCEAR Global Survey. The meanfrequency of diagnostic radiology procedures in the countries in the survey is 1,038 examinations per
1,000 population, constituting by far the highest contribution (97.8%) to the total frequency of medical
radiological procedures per 1,000 population. On average, projection radiography (without dental
procedures) accounts for 59.8%, radiography and fluoroscopy 2.0%, dental procedures 25.2% andcomputed tomography 13.0% of all diagnostic radiology procedures. The data from the survey and theliterature review indicate a slight increase in the overall frequency of X-ray procedures in general(combining diagnostic radiology and interventional radiology) and nuclear medicine frequencies (seefor more details appendix D); however, for some types of examinations and in some countries there arealso decreasing trends. The average increase in diagnostic radiology examinations is most remarkablefor chest (thorax), mammography, limbs and joints, dental panoramic examinations, coronary
angiography, chest scans and abdomen scans. The average decrease is most notable for projection
radiography of the thoracic spine, lumbar spine, abdomen, and gastrointestinal tract (barium studies).
B93.
Data on frequencies and collective or per caput effective doses as a function of age and sex
have not been widely published. The results from 11 countries in the survey indicate that the age
distributions of examination frequencies for each modality are roughly similar across countries;
however, the proportions of older and younger patients differ for some countries. Differences may
reflect national preferences in imaging practice and/or differences in population age distributions.
Differences in the age distributions of frequencies between the two sexes are not very high except for
projection radiography, where a significantly higher proportion of examinations are performed forfemales between about 40 and 70 years, mainly due to mammography. In paediatric examinations,children older than 10 years seem to be the most frequently exposed, whereas children younger than
5 years are the least frequently exposed. About half of paediatric examinations are in conventional
radiology and dental radiology while computed tomography and diagnostic interventional radiology
account for just a few per cent of the total. Age and sex distributions of frequencies from the few
published studies indicate roughly similar shapes as in the survey.
B94.
The UNSCEAR Global Survey and the published studies indicate large variations between
different countries in the typical effective doses for examinations. However, there are no great
differences in any diagnostic radiology subcategories when the mean effective dose calculated from thesurvey data is compared with various publications. From the survey data, the highest typical effective

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doses in (a) projection radiography (>1 mSv) are for whole spine (trunk), pelvis (soft tissue) andlumbar spine; in (b) radiography and fluoroscopy (>6 mSv) for abdominal, pelvic, cerebral and cardiac
angiographies and biliary tract (cholangiography); and in (c) computed tomography (>11 mSv),
examinations of the trunk (chest, abdomen and pelvis), full spine (neck, chest and abdomen) and two
types of computed tomography examinations of the abdomen. Within computed tomography
examinations, dental computed tomography examinations have the lowest effective dose (0.3 mSv orless). Except for mammography and for examinations of the head region, for all diagnostic radiology
procedures the effective dose calculated using ICRP 103 [I11] tissue weighting factors is lower thanthat calculated using ICRP 60 [I9] factors. The increase in effective dose for mammography is due tothe increase in the weighting factor for the breast. For paediatric data, differences between age groups
and with adults vary greatly between examination types; effective doses for computed tomography
procedures are generally quite similar to those of adults, for fluoroscopy procedures doses seem to beconsistently lower, and for plain radiography the results are mixed. The results of the UNSCEAR
Global Survey together with reviewed publications suggest that typical (mean) effective doses havegenerally decreased during the past decade, although significant increases in a few large countries, orthe shortage of data in some cases, lead to average values that indicate increased typical dose for some
types of projection radiography and computed tomography examinations.
B95.
The literature review indicates that X-ray procedures (diagnostic radiology and interventional
procedures) make a major contribution to the total collective effective dose and effective dose per caput
from all medical imaging, 92% on average. The contribution of computed tomography examinations to
the total per caput effective dose is typically much more than their contribution to the total frequency:from the literature review, the mean contribution to the total per caput effective dose is 52.5% and therange from 5.3% to 79.0% (about 15-fold variation) while the contribution to total frequency is only
9.0% with the range from 0.7% to 25.5% (about 36-fold variation). Dental procedures are typically 10
to 40% of the total frequency but contribute less than 1% to the total per caput effective dose.
Conventional fluoroscopy is typically a few per cent of the total frequency, but the mean contribution to
the total per caput effective dose is 9.7%. Interventional radiology is typically less than 1% of the totalfrequency but the mean contribution to the total per caput effective dose is 8.2%.
B96.
The data on the numbers of professionals and of diagnostic radiological systems and devices
generally show great variation between countries. For example, recent literature indicates that the
number of medical physicists is highest in Europe (34% of the total number of medical physicists),
followed by North America (33%) and Asia/Oceania (24%). From the total number of diagnostic
systems, on average, still more than half (about 56%) used are analogue systems. The majority ofcomputed tomography scanners are multi-slice scanners and, on average, less than 5% are single-slice
scanners (excluding dental and cone-beam scanners).
B97.
The development of imaging technology plays an important role in the trends in imaging
practices, numbers of examinations and patient dose levels. The major changes in imaging technology,
such as the replacement of conventional film-screen systems by digital techniques, the replacement ofcomputed radiography techniques by direct digital techniques, and the development of new detectors
with higher detective quantum efficiency have had a recognized impact on imaging practices andpatient dose levels, as already noted in the previous UNSCEAR report [U9]. In computed tomography,
the development of technology during the past 10–15 years has had a pronounced effect both on thenumber of computed tomography examinations and on patient dose levels. Single-slice scanners havebeen largely replaced by multi-slice scanners, and the improved efficiency of modern multi-slice
scanners has contributed to the increase in the number of computed tomography examinations while
also broadening the use of computed tomography into new applications. Also, in cardiac radiology, thedevelopment of computed tomography scanning technology has progressed with significant dosesavings: among the major factors contributing to this dose reduction is the availability of dose efficientANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

205

scan protocols with a reduced tube potential, prospective ECG-triggering and iterative image
reconstruction. However, there is extensive variation in the availability of these new technologies
worldwide and, in many low-income and lower middle-income countries, the level of technology is stilllargely non-digital, based on older techniques and often lacking appropriate provisions for patient dosemonitoring (such as DAP meters). It should be noted, further, that there are not major patient orequipment differences to explain the large variations in patient doses across countries, but the variation
comes mainly from how the equipment is used and thus suggests room for optimization.
B98.
The results of the UNSCEAR Global Survey and the literature review have shown that theearlier trend of increasing collective effective dose and per caput effective dose in medical imaging has
continued in the past ten years but has been less significant than in the previous decade. The increase
has been caused mainly by continued increasing use of high dose procedures, in particular computed
tomography, but also some interventional procedures and nuclear medicine procedures (see also
appendices C and D). For computed tomography, it has been shown that the observed rise in use cannot
be primarily attributed to the growth and ageing of the population. Nevertheless, despite the increased
use of computed tomography, the increase of collective effective dose from computed tomography has
slowed in some cases due to the development of dose-saving technologies.

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APPENDIX C. LEVELS AND TRENDS OF EXPOSURE IN
INTERVENTIONAL RADIOLOGY

I. INTRODUCTION
C1.
Interventional radiology has been defined internationally in a range of ways. Future surveys on
medical exposure would benefit from adopting common terminology and a common methodology inrelation to interventional radiological procedures. For example, the International Basic Safety Standards[I3] uses the term “image guided interventional procedures” also used by the Committee in its
UNSCEAR 2008 Report [U9], which described it as "fluoroscopic guidance frequently utilized inperforming many interventional techniques, including precision diagnostic and therapeutic injection
procedures". The European Basic Safety Standards Directive [E4] defines “interventional radiology” as"the use of X-ray imaging techniques to facilitate the introduction and guidance of devices in the bodyfor diagnostic or treatment purposes". The International Commission on Radiological Protection(ICRP) in its publication 120 calls it “fluoroscopically guided interventions”, which are "procedures
comprising guided therapeutic and diagnostic interventions, by percutaneous or other access, usually
performed under local anaesthesia and/or sedation, with fluoroscopic imaging used to localize thelesion/treatment site, monitor the procedure, and control and document the therapy" [I14]. Anotherdefinition given by the National Council on Radiation Protection and Measurements (NCRP) says that
“interventional fluoroscopy” refers to "any procedure in which the use or application of a medical
device is fluoroscopically guided in the body, and includes procedures that are performed for diagnostic
and therapeutic purposes" [N1]. The International Electrotechnical Commission (IEC) calls a"radioscopically guided interventional procedure" "an invasive procedure, involving the introduction ofa device, such as a needle or a catheter into the patient, using radioscopy as the principal means of
guidance and intended to affect treatment or diagnosis of the medical condition of a patient" [I18].
C2.
A consensus statement was signed by many national interventional radiology organizations in2010 [K5]. It stated that “interventional radiology originated within diagnostic radiology as an invasive
diagnostic subspecialty. It is now a therapeutic and diagnostic specialty that comprises a wide range ofminimally invasive image-guided therapeutic procedures as well as invasive diagnostic imaging. The
range of diseases and organs amenable to image-guided therapeutic and diagnostic procedures areextensive and constantly evolving, and include, but are not limited to, diseases and elements of thevascular, gastrointestinal, hepatobiliary, genitourinary, pulmonary, musculoskeletal and, in somecountries, the central nervous system”. The scope of interventional radiology as agreed in the consensus
statement [K5] was:−

Evaluation and management of patients with diseases or conditions amenable to image-guided
interventions;−

Invasive diagnostic imaging with the exception of invasive cardiac imaging;−

Minimally invasive image-guided and related procedures of vascular, gastrointestinal,
hepatobiliary, genitourinary, pulmonary, musculoskeletal, and, in some countries, neurologicalconditions amenable to these procedures;−

Diagnostic imaging as relevant to local practice.

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Cardiac interventions were excluded from this consensus statement as it was signed only byinterventional radiology organizations and not interventional cardiology organizations [K5].
C3.
The Committee, in its UNSCEAR 2000 and 2008 Reports [U6, U9], already recognizedinterventional radiology as an established part of mainstream medicine and expected that it is likely to
expand further with the continuing development and adoption of new procedures, particularly incountries with well-developed health-care systems. In the last decades, the advances in technology for
imaging and ancillary equipment have facilitated the development of increasingly complex radiologicalprocedures for angiography and interventional radiology which traditionally is performed underfluoroscopy guidance using angiography systems. However, the use of angiography systems forinterventional radiological guided procedures causes problems when accounting for radiologicalexaminations based on the device used. Thus, the use of the term “interventional fluoroscopy systems”
as defined by IEC [I18] could be used in the future “X-ray equipment for radioscopically guided
interventional procedures”.
C4.
According to the user manual for the UNSCEAR Global Survey [U11], interventional
radiological procedures, was defined in the past as "any minimally invasive procedure performed underfluoroscopy guidance with therapeutic purpose and may involve any cerebral, cardiac, pulmonary,
hepatobiliary, gastrointestinal, genitourinary, musculoskeletal and central nervous system disease". Any
minimally invasive procedure performed under fluoroscopy guidance with diagnostic purpose is part ofthe modality category: radiography and fluoroscopy (mostly with contrast media). The latter definition
was used for the analysis of data of the current survey.
C5.
The literature review showed that countries report differently fluoroscopy, diagnostic andtherapeutic interventions, as shown in table C1. Certain countries treat diagnostic and therapeutic
procedures as one category. Distinction from diagnostic and analysis of therapeutic procedures was
possible only for three out of 12 national surveys. In two surveys, only diagnostic procedures werereported, as statistical data on therapeutic procedures were not collected at national level.
Table C1. Reporting of interventional radiological procedures according to different surveys
PTCA: Percutaneous transluminal coronary angioplasty
Included procedures

National surveys

Only diagnostic proceduresFrance [D10, E11], Republic of Korea [L3]

Only therapeutic procedures

Luxembourg [S12], Portugala [T3], Ukrainea [S22]Diagnostic and therapeutic in one category

Australiab [H6], Finland [B19], Germany [N3], Ireland [O1],
Kenyab [K13], Norway [B25], Romania [G5], Spain [S4],Taiwan, China [C6], USA [N1]

Diagnostic and therapeutic in separate categories

Slovenia [Z1], Switzerland [A8, S2, S3], UK [H5]aOnly PTCA based on the TOP 20 methodology [E3].

bWith possible separation of procedures for UNSCEAR Global Survey.

C6.
The number of interventional procedures performed under computed tomography guidance isincreasing and, in future, the definition of interventional procedures should also take this into account.
In most of the countries, computed tomography interventions are now accounted for under the“computed tomography” category.

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209

C7.
Furthermore, modern C-arm equipment can acquire multiple projections by rotating the flat
panel detector around the patient. These projections are used to reconstruct tomographic images, known
as cone beam computed tomography (CBCT) images. These images present multiple planes of vessels
and are used in conjunction with digital subtraction angiography and fluoroscopy to increase safety andefficacy of procedures.
C8.
Recognizing the continuous development of techniques, skills, methods and processes thatlead to an increasing number of interventional procedures, and also the various definitions ofinterventional radiology worldwide, the following updated definition is proposed for future surveys
even though it is not applied to the current evaluation: “an interventional procedure refers to theinsertion and positioning of a device into the body under fluoroscopic and/or computed tomography
guidance for diagnostic and/or therapeutic purposes. Interventional procedures include those performed
in or outside of radiology departments”.

II. RECAPITULATION OF PREVIOUS UNSCEAR REPORTS
C9.
In the UNSCEAR 2000 Report [U6], which covered the period 1991–1996, interventional
procedures were accounted for under diagnostic radiology along with projection radiography,
fluoroscopy, mammography, computed tomography, angiography and dental radiology. The worldwide
contribution to procedure frequency and collective dose for interventional procedures for 1991–1996
was estimated to be 0.3 and 4%, respectively [U6]. Percutaneous transluminal coronary angioplasty(PTCA) procedures were identified to increase with considerable variation among different countries.
C10.
In the UNSCEAR 2008 Report [U9], which covers the period 1997–2007, interventional
radiology was again accounted for under diagnostic radiology, but this time more data on frequencies
and doses for interventional radiology and cardiology were available. Data on cardiac PTCA, as theleading interventional procedure in terms of frequency and dose, are presented here, and also under thebroad category “other interventional procedures”. The contribution of interventional procedures to thefrequency of diagnostic medical and dental radiological examination in the UNSCEAR 2008 Report[U9] was estimated to be 0.1% worldwide (table C2).
Table C2. Frequency of interventional procedures according to UNSCEAR 2008 Report [U9]PTCA: Percutaneous transluminal coronary angioplasty; HCL: Health-care level
Procedure

HCL I

HCL IIHCL III–IV

World

Number of examinations per 1 000 populationa
PTCA

0.9

0

0

0.3

Other interventional

1.1

0

0

0.3

Contribution to the frequency of medical and dental examination (%)a

a

PTCA

0.10

0.03

0

0.05

Other interventional

0.10

0.01

0

0.05

Values are rounded; however extended precision has been preserved to illustrate differences.

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UNSCEAR 2020/2021 REPORTC11.
The global annual collective effective dose for interventional procedures for 1997–2007 wasestimated to be about 41,000 man Sv. The collective dose by health-care levels for the same period ispresented in table C3. Further, in the UNSCEAR 2008 Report [U9], it was identified that about half ofthe collective effective dose due to diagnostic radiology arose from three procedures: computed
tomography, angiographic examinations and interventional procedures. A major increase in the numberof PTCA procedures was also noted between 1997 and 2007 [U9].
Table C3. Collective dose of interventional procedures according to UNSCEAR 2008 Report [U9]PTCA: Percutaneous transluminal coronary angioplasty; HCL: Health-care level
Procedure

HCL I

HCL IIHCL III–IV

Collective effective dose (man Sv)

World
a

PTCA

17 0003 800

021 000

Other interventional

19 0001 100

020 000Contribution to the collective effective dose of medical exposure (%)a,b
PTCA

0.57

0.37

0

0.53

Other interventional

0.69

0.10

0

0.56

a

Values are rounded; however extended precision has been preserved to illustrate differences.

b

Excluding exposure from nuclear medicine procedures.

III. FREQUENCIES OF PROCEDURES
C12.
This section presents information on trends in the frequencies of interventional procedures
resulting from the submissions to the UNSCEAR Global Survey. Furthermore, the data were
supplemented with information from reviews of the published literature.

A. UNSCEAR Global Survey data
C13.
In the current UNSCEAR Global Survey, detailed data (frequency and dose data) from 38
countries have been received for interventional procedures. Unfortunately, the data for many countries
were incomplete and did not provide a basis for accurate evaluation of the population doses, i.e.,collective effective doses and per caput effective doses. Data on the frequencies of examinations (i.e.,annual numbers of examinations) are more complete, but the submitted dose data kerma in air area
product (KAP) values or typical effective doses were scarce. Some countries submitted totalfrequencies but did not provide numbers for the individual procedures while other countries provided
procedure frequencies but no data on doses (see also electronic attachment C-1).

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211

C14.
The frequency data from the current UNSCEAR survey for interventional procedures areshown in figure C-I and table C4. The frequencies are recorded per 1,000 population to allow forcomparison with other radiological examinations. Some countries provided data only for the total
number of interventional procedures. There is a very wide variation in procedure frequencies across theworld, with the highest frequencies occurring in Estonia, Hungary, Lithuania and the United States.
C15.
The frequency of interventional procedures per 1,000 population has increased significantly inseveral European countries. Apart from the increase in the number of interventional procedures
conducted worldwide, there are differences to the previous UNSCEAR 2008 Report [U9]. In the
UNSCEAR Global Survey more information on interventional procedures were collected and that themethod of data collection has been changed. For example, (a) the Russian Federation provided data on
PTCA procedures with fluoroscopy data and interventional radiology procedures including only
abdominal interventions; (b) Spain accounted data on endovascular surgeries as interventional
radiology procedures; and (c) Germany accounted balloon angioplasty, atherectomy, rotablation,
selective thrombolysis, selective embolization, balloon valvuloplasty, stent implantation andpercutaneous myocardial revascularization as PTCA procedures.
Figure C-I. Frequency of interventional procedures per 1,000 population reported in UNSCEAR
Global Survey

212

Table C4. Frequency of annual interventional procedures per 1,000 population reported to UNSCEAR Global Survey

Frequency of procedures per 1 000 population a,b
Head(cerebralintervention)

PTCA

Argentina

0.15

2.96

Australia

0.03

1.67

Country

Chest(pacemaker)

Thoracicintervention(other)Abdomen(biliary andurinaryintervention)

Abdomen(TIPS)

0.58
1.54

0.10

Abdominal
interventions(other)Pelvicinterventions

0.18

0.27

0.05

Limb
interventions

Others c

Total

4.1
1.03

2.95

7.4

Bangladesh

10Belarus

14.6

Belgium

0.11

2.30

0.04

1.02

0.02

0.10

0.004

0.06

3.32

7

Brazil0.42

Brunei Darussalam

2

Bulgaria

0.07

3.37

0.46

13.51

17.4

Canada

12.4

Chile

0.08

Cyprus

1.69

Czech Republic

2.17

Denmark

1.96

Estonia

0.08

1.36

France1.75

Germany

8.37
0.02

1.03

4.95

3.32

0.01

6.72

0.03

0.60

1.24
0.47

0.001

Indonesia

0.06

2.05

6.81

11.1

6.91

8.7
1.8

0.34

0.0003

Hungary
Iceland

18.2
2

2.95

Finland

Greece

1.7

1.36

0.17

0.15

0.11

0.36

0.25

8.25

16.6

0.12

1.1

30.56

30.6

2.40

6.9
0.03

UNSCEAR 2020/2021 REPORTPTCA: Percutaneous transluminal coronary angioplasty; TIPS: Transjugular intrahepatic portosystemic shunt

Frequency of procedures per 1 000 population a,bCountryHead(cerebralintervention)

Lithuania
Luxembourg

PTCA

Chest
(pacemaker)

Thoracicintervention(other)Abdomen(biliary andurinaryintervention)

Abdomen(TIPS)

Abdominal
interventions(other)Pelvicinterventions

Limbinterventions

17.86
0.28

3.15

1.11

1.25

4.13

0.002

0.37

0.34

1.88

Malaysia
Netherlands

0.05

Norway

8.04

0.26

0.85

0.24

0.49

Others c

Total

11.91

29.8

0.82

13.3

8.24

8.2

0.93

10.9

2.27

2.3

Philippines
0.24

4.18

0.27

Romania

0.05

0.92

0.08

Russian Federation

0.19

0.001

0.22

0.07

0.001

0.01

0.01

0.0001

0.001

0.62

1.38

7

0.03

0.01

0.06

1.06

2.2

0.49

8.99

10.7

0.44

0.49

0.15

San Marinoa4.6

Slovenia

1.85

4

5.9

Spain

1.78

6.78

8.6

Sweden

2.20

0.30

2.5

Switzerland

3.26

1.65

4.9

United Arab Emirates

0.30

1

0.13

2.09

0.21

0.030

0.19

0.10

0.62

United Kingdom

0.08

0.30

0.59

2.34

0.59

0.01

1.05

0.60

1.47

2.45

9.5

United States

0.07

2.63

1.11

1.26

0.49

0.59

0.16

1.31

11.05

18.7

Values are rounded; however extended precision has been preserved to illustrate differences.

b

Empty cell indicates no data available.

cIncludes any procedures that were reported as “others” or did not fit any of the specific categories so that the total number of interventional procedures sum correctly.

4.7

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

Poland

0.01

213

214

UNSCEAR 2020/2021 REPORTC16.
The most commonly performed interventional procedure is the PTCA procedure, followed byinterventions performed at the level of the chest and abdomen/pelvic regions (biliary and urinary). In
figure C-II, the contribution of PTCA to interventional procedures is displayed. The mean contribution
is 48%, ranging from 3% to 100%, as some countries provided data only on PTCA procedures.
C17.
Data on other examinations were reported by certain countries. Unfortunately, the scarcity ofdata did not allow a thorough analysis; thus, all examinations were treated as one modality category.
Moreover, in some cases the total number of interventional radiology procedures did not match with thesum of the specific interventional radiology procedures. In these cases, the difference was added to the“other” procedures. The large number of “other” interventional procedures shows that an update of thelist of procedures in the current survey may be needed in the future to cover development in theinterventional radiology domain.
Figure C-II. Contribution of PTCA to annual frequency of interventional procedures as reported to
UNSCEAR Global Survey
PTCA: Percutaneous transluminal coronary angioplasty

C18.
Table C5 presents a comparison in frequency data for cerebral interventions and PTCA
between UNSCEAR 2008 Report [U9] and this survey. The number of PTCA procedures seems to berather stable or to increase between 2008 and this survey, while for cerebral interventions large
differences are observed between countries. Any change in the methodology followed by individual
countries for counting frequencies during this period may also contribute to large variations. Note thatin the UNSCEAR 2008 Report [U9], cerebral angiography was a subcategory of interventional
procedures, however, these procedures could be also considered diagnostic, which requires attention
when comparing these data.

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215

Table C5. Comparison of frequency of cerebral interventions and PTCA procedures per 1,000
population as reported to UNSCEAR Global Survey and in UNSCEAR 2008 Report [U9]PTCA: Percutaneous transluminal coronary angioplasty

Country

Frequency per 1 000 procedures
Head (cerebral intervention) a
Current
evaluation

UNSCEAR2008 Report b

Change(%)

Frequency per 1 000 procedures
PTCA aCurrent
evaluation

UNSCEAR2008 Report

Change
(%)

2.30

1.90

21

Czech Republic

2.17

0.78

182

Finland

1.36

1.88

−28

France

1.75

1.71

2

Germany

8.37

2.30

264

Iceland

2.05

1.97

4

Lithuania

17.86

2.19

716

3.15

1.54

105

Norway

2.27

0.54

320

Romania

0.92

0.73

26

Slovenia

1.85

1.80

3

Spain

1.78

0.65

174

Switzerland

3.26

1.05

210

0.30

0.44

−32

Belgium
Bulgaria

0.07

0.66

−89

Luxembourg

0.28

0.07

300

Netherlands

0.05

1.21

−96

United Kingdom

0.08

0.03

167

a

Empty cell indicates no data available.

b

Cerebral angiography was considered as interventional procedure in UNSCEAR 2008 Report [U9].

B. Literature review data
C19.
The population dose from interventional radiological procedures was reported in 22 of thereviewed articles, corresponding to 17 individual countries and one region (Europe). The populationdose from interventional procedures depends on a number of factors, namely the:−Availability of interventional radiology facilities, including appropriately trained staff;−

Type of procedure (e.g., cardiac, vascular);−

Methodology chosen for the estimation of population exposure in general (e.g., X-ray only or
nuclear medicine procedures included, national survey versus reimbursement systems);−

Type of procedures considered as interventional radiological procedures (e.g., fluoroscopy or
diagnostic interventional procedure followed by a therapeutic procedure or only therapeuticinterventional procedures);

216

UNSCEAR 2020/2021 REPORT−Type of X-ray units and its capabilities (e.g., image-intensifier, flat panel detectors, over- or
under-couch, continuous fluoroscopy, pulsed fluoroscopy, additional Cu filter for skin sparing,
digital subtraction angiography, acquisition of 3-D images with C-arms) and, thus, theexposure parameters used during the interventional procedures;−

Level of optimization applied in the imaging protocols;−

Tissue weighting factors used for the calculation of the effective dose according to ICRP 60[I9] or ICRP 103 [I11];−

Medical specialties in addition to radiologists and cardiologists performing interventional
procedures (e.g., vascular surgeons).

C20.
Table C6 presents the contribution, in terms of effective dose and frequency of interventional
radiological procedures to population medical exposure in different countries as reported in theliterature. The contribution of interventional procedures to the total number of medical radiologicalimaging procedures was relatively small, ranging from 0.03 to 14.2% (average 2.3%). However, thecontribution to the population dose in percentage terms was higher (4 to 23%, average 8.6%), resulting
in an average population dose of 0.07 mSv per caput. A wide range of reported effective doses (ranging
from 0.001 mSv in Kenya to 0.14 mSv in Ireland) was observed for different countries. Although thesearticles were reported as national surveys that had been conducted over a large period (2002–2013)
there was no correlation between per caput effective dose and the year of study.
C21.
The methodology followed for the national surveys has a direct impact on the results. Two
major points should be taken into account: (a) procedures included in a survey, and (b) type ofprocedures considered as interventional radiological procedures. In some countries, the total number ofprocedures includes only X-ray procedures (such as in Finland, Kenya, Romania and Switzerland); inothers, it includes X-rays and nuclear medicine (such as in Australia, Ireland, Luxembourg and UnitedStates). In Norway, ultrasound and magnetic resonance imaging (MRI) examinations were included
with X-ray procedures. Some countries, such as Portugal, Slovenia and Ukraine, followed the TOP 20
methodology developed by EC DDM 1 [E3]. The TOP 20 methodology includes only PTCA asinterventional procedure. Although the PTCA procedure is the most frequent, the methodology
considerably underestimates the total number of interventional procedures [B20]. Thus, some countries
applied correction factors for improved estimations (Slovenia and Ukraine).
C22.
In certain countries, the frequencies of interventional procedures and doses of both diagnostic
and therapeutic procedures were accounted as one category, while other countries accounted only fortherapeutic procedures or only for diagnostic procedures. The data of the latter are presented inappendix B on diagnostic radiology.

Table C6. Radiation doses and frequencies of interventional radiological procedures in different countries as reported in the literature
Based on data published between 2006 and 2017. Data on exclusively therapeutic interventional procedures are in italic
CountryYear

Frequency per 1 000
population a,bCollective dose(man Sv) a,b

Contribution tofrequencies(%)a,bContribution to
population dose(%)a,b

Per caput effective
dose(mSv) a,b

Reference

0.3

1.4

0.02

[H6]

14

0.06

[B19]

Australia

2010

530

Finland

2008

336

Ireland

2013

630

0.90

23

0.14

[O1]

Kenya

2011

43

0.02

2.0

0.001

[K13]

Luxembourg

2002

6

0.12

[S12]

Macedonia (Theformer Yugoslav
Republic of)

2010

0.44

Norway2002

13

Portugal

2010

1.16

Romania2012

Slovenia

2011

142

Spain

2015

663

Switzerland

2008

Switzerland

2013

Taiwan, China

2008

Ukraine2012

United Kingdom

2008

2 037

United States

2008

94 000Europe 36 countries

2010

3

178

83

a

Values are rounded; however extended precision has been preserved to illustrate differences.

b

Empty cell indicates no data available.

0.14
0.3

2

0.6

11

[G3]
0.03

[B25]

0.017

[T3]
[G5]

0.07

[Z1]

0.01

[S4]

0.4

6

0.07

[S2]

0.4

6.2

0.09

[L2]

16.2

~0.1

[C6]

0.5

0.005

[S22]

0.03

4

8

[H5]

14

[N1]

8

0.06

[B20]

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

3

5

0.4

4

217

218

UNSCEAR 2020/2021 REPORTC23.
The EC DDM 2 project [E5] provided comprehensive information on 36 European countries
regarding frequencies and radiation dose of X-ray and nuclear medicine diagnostic procedures fromnational surveys carried out between 2007 and 2010. On average, the total annual frequency ofinterventional procedures in Europe was six examinations per 1,000 population while their relative
contribution to the overall collective effective dose was 9%. The mean effective dose per caput was
0.09 mSv. Typical doses for PTCA examinations in Europe ranged from 4 to 29 mSv with a mean valueof 15.2 mSv. Large variation in the total number of interventional radiology examinations was observed
among European countries. Interventional radiological procedures in the EC DDM 2 project included
both diagnostic and therapeutic procedures. Some countries reported completed data while others
followed the TOP 20 methodology [E3], which counted only the PTCA procedure as the most common
interventional procedure. This may explain some of the large variations in frequency and doses ofinterventional procedures across Europe.
C24.
Only Costa Rica focused on the estimation of the collective dose to the paediatric population
deriving from interventional cardiac procedures (diagnostic and therapeutic) [U2]. The frequency of
paediatric interventional radiology procedures per million population per year for the entire paediatricpopulation (0–16 years) was 31.7 procedures. Collective dose for the children aged 0–16 years per
million population was 0.16 man Sv while for the whole population this figure was 0.78 man Sv. These
data are not presented in table C6, as it concerns only paediatric patients.

1.

Most contributing procedures

C25.
The literature review confirmed that cardiac procedures were the most frequent interventional
procedures worldwide. In Australia, the two most common interventional procedures were reported by
Hayton et al. [H6] with 87% for coronary angiography and 13% for PTCA. In Ireland, interventional
procedures accounted for only 0.9% of examinations but contributed 23% to the collective dose. Theinterventional procedures category included both diagnostic and therapeutic interventional procedures,
while procedures performed in operating theatres were also considered [O1]. Interventional proceduresin Kenya’s survey [K13] included various cardiac and non-cardiac procedures. Coronary angiography
was by far the most frequent procedure with 46% of the total while other cardiac procedures, such as
PTCA, percutaneous mitral valve dilatation and pacemaker contributed around 10% each (table C7).
Abdominal and pelvic procedures were less frequent.
C26.
In Luxembourg, interventional procedures were divided into cardiac and vascular [S12], while
in Romania, the most frequent procedures were cardiac interventions (51% coronary angiography and23% coronary angioplasty) [G5]. In Taiwan, China [C6], interventional procedures were divided into
non-cardiac and cardiac procedures and showed equal contribution to the total exposure of the
population. In the United States [N2], interventional procedures are divided into cardiac and noncardiac interventional fluoroscopy procedures. The estimated total number of cardiac procedures was
4.1 million cases per year contributing to 0.6% of the total number of procedures and 6% to thecollective effective dose. It is worth noting that more coronary diagnostic and percutaneousinterventions are combined in a single procedure, the number of electrophysiological procedures isincreasing, and a much smaller (but rapidly increasing) number of structural heart procedures exists.

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

219

Table C7. Distribution of interventional radiological procedures in Kenya in 2011 [K13]
PTCA: Percutaneous transluminal coronary angioplasty
Interventional procedure

Distribution (%)

Vessel angiography

7.1

Embolization

0.3

Biliary drainage

2

Cardiac angiography

45.7

Fallopian tube catheter

2.5

Inferior vena cava filter implantation

0.5

Lower limb arteriography

4.1

Nephrostomy

2.1

Pacemaker

11.1

Percutaneous mitral valve dilatation

11.8

PTCA

8.8

Pulmonary balloon valvuloplasty

2.2

Renal angiography

1.1

Vasography

0.8

C27.
A study in Spain considered primarily cardiac procedures in the estimation of the annual
collective dose from interventional procedures and, due to the small number of procedures other than
PTCA, only PTCA data were considered. PTCA represented 96% of the interventional cardiac
procedures, 3% of the procedures concerned structural heart disease and only 1% adult cardiac
congenital disease [S4]. In Switzerland, a survey divided the interventional procedures into diagnostic
and therapeutic [S2]. Coronary angiography was found to be most frequent, followed by PTCA
procedures (34% and 18% of interventional procedures, accordingly). However, the contribution of
PTCA procedures to the collective dose was 29% while for coronary angiography it was 35%.
C28.
The general category “angiography/fluoroscopy” in the study by Smith-Bindman et al. [S18]in the United States included abdomen, cardiovascular and other procedures. Their corresponding
contribution was 22, 69 and 11%, respectively. In conclusion, the review of the literature conductedhere showed that in all countries cardiac interventional procedures were the most frequent andcontributed the most to the collective dose from interventional procedures.

220

UNSCEAR 2020/2021 REPORT

IV. DOSES FOR INTERVENTIONAL PROCEDURES
A. UNSCEAR Global Survey data
1.

Typical effective doses per procedure

C29.
Typical effective doses were reported to the UNSCEAR Global Survey by countries for thedifferent interventional radiology procedures. Some countries have reported frequencies (annual
numbers of interventional procedures) but no dose data (neither KAP nor effective doses) for any typeof interventional procedures. For these countries, typical effective doses per interventional procedure
were calculated on the basis of the following assumptions:−

KAP with a conversion factor was used to calculate the typical effective dose whenever the
KAP was reported. The conversion factors are presented in table C8 for each type ofprocedure. Most of the conversion factors were given in the user manual for the UNSCEAR
Global Survey [U11], while others were taken from the literature review;−

If no KAP was reported, but the effective dose was provided by the country, this was useddirectly;−

If neither KAP nor effective dose was reported, the mean KAP by other countries was adopted
and the typical effective dose was calculated with a conversion factor; otherwise, the meaneffective dose reported by other countries was adopted;−

For “other” interventional procedures, which is the only category when no KAP or effective
dose from any country was reported, the mean effective dose from all procedures was used.

Table C9 summarizes the results of effective doses per procedure used in this evaluation.
Table C8. Conversion factors for interventional procedures used for effective dose calculations in
UNSCEAR Global Survey
PTCA: Percutaneous transluminal coronary angioplasty; TIPS: Transjugular intrahepatic portosystemic shunt
Conversion factor (mSv/(Gy∙cm2))

Reference

Head (cerebral intervention)

0.10

[S6]

PTCA

0.26

[N1]

Chest (pacemaker)

0.10

[N1]

Thoracic intervention (other)

0.12

[N1]

Abdomen (biliary and urinary intervention)

0.26

[N1]

Abdomen (TIPS)

0.26

[N1]

Abdominal interventions (other)

0.12

[C14]

Pelvic interventions

0.18

[N1]

Limb interventions

0.23

[C14]

ProcedureANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

221

Table C9. Effective doses of interventional procedures reported to UNSCEAR Global Survey
PTCA: Percutaneous transluminal coronary angioplasty; TIPS: Transjugular intrahepatic portosystemic shunt

Australia
13.1

38

Bulgaria

10.7

30.2

Czech Republic
9.1

France

19
11

Other

Other

TIPS

Limbs

Biliary and urinary

0.6

6

29.1

Iceland

5.2
6

Norway109Greece

44

32

11

1.3

2.5

16.1

11.7

24.8

17

Republic of
Korea

31.7

Romania

3.2

RussianFederation

4.5

19.6
6.7

14.8

Spain

28.6

Sweden8.1

Switzerland

33.8

UnitedKingdom

13.5

Uruguay

16.6
11.2

1.7

2.4

2.3

5.8

Slovenia

Average

Other

31.1
16.6

Lithuania

Abdomen

19.4

FinlandGermany

Pace-maker

21.6

Belgium

Estonia

Chest

PelvicPTCA

Country

CerebralEffective dose per procedure (mSv) a,b

19.7

0.7

2.8

2.7

53.3

2.3

23.4

6.7

27.8

a

Values are rounded; however extended precision has been preserved to illustrate differences.

b

Empty cell indicates no data available.

32

3

1.9

9.3

11.2

7.8

10.2

13.9

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UNSCEAR 2020/2021 REPORTC30.
Table С10 compares mean KAP values (and their standard deviations where provided), as
reported by different countries to the UNSCEAR Global Survey for cerebral and PTCA interventions
with KAP values provided in the UNSCEAR 2008 Report [U9] by the same countries. Large standard
deviations, and variations in KAP values for both procedures are observed for some countries andthroughout the years.
Table С10. Comparison of mean KAP values for cerebral interventions and PTCA reported to
UNSCEAR Global Survey with UNSCEAR 2008 Report [U9]PTCA: Percutaneous transluminal coronary angioplasty
Mean KAP (Gy cm2) ±standard deviation a
Cerebral intervention

Country

Current
evaluation

PTCA

UNSCEAR2008 [U9]Australia
Belgium

131±99146±124116±143

Czech Republic

52
91±50

75±37

64

Greece112±54

Iceland20±28

Lithuania

60±3

Republic of Korea

317

Romania

32

26
57
77

SwedenSwitzerland
United Kingdom
Uruguay
Empty cell indicates no data available.

78

62±2

Slovenia
Spain

120

120±78Finlanda

UNSCEAR2008 [U9]83±11Bulgaria

Estonia

Current
evaluation

110±25

68

31
50

130
52±27
64

85

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

223

C31.
Table С11 summarizes typical effective doses of various interventional procedures used forthe calculation of medical exposure in different countries as reported in literature. PTCA was theprocedure largely studied. Large variations were observed; the minimum effective dose was 7.2 mSv
and the maximum 86 mSv with a median value of 17 mSv. In most cases, effective doses were
calculated using ICRP 60 [I9].
Table С11. Average effective doses used for calculating population doses from adult interventional
procedures
PTCA: Percutaneous transluminal coronary angioplasty
Country /regionAverage effective dose (mSv) a
Head(cerebral)

PTCA

Australia

17

Italy

47

Chest
(pacemaker)

Chest(other)Abdomen(biliary/urinary)

Reference
[H6]

0.7

[P8]
10

Kenya

Limbs

86

3

89

b

c

9d

[K13]

41e
Norway11.4

Portugal
Romania
Switzerland

[B25]

14.5
6.3f

[T3]

21.7

4.8e

6.1

[G5]

17

17

18

[S2]

c

20

a
b
c
d
e
f
g
h
i

China, Taiwani

7.2

United States

23

Europe

15.2

h

[L2]
32.3g
1

[C6]
[N1]
[E5]

Empty cell indicates no data available.
Pulmonary balloon valvuloplasty.
Drainage.
Nephrostomy.
Renal angioplasty.
Carotid angioplasty.
Trans arterial embolization.
Lower limb dilatation.
Applied ICRP 103 tissue weighting factors [I11].

C32.
Table C12 presents typical KAP values and some conversion factors mSv/(Gy cm2) that wereused for the calculation of the effective dose of different interventional procedures in a limited numberof hospitals and surveys. The large variation that is observed in the KAP values for all interventional
procedures is attributed to patient-, technology- and operator-related factors. Conversion factors are
expected to vary with patient size, X-ray energy distribution, field size and body part exposed and, thus,
consideration of their application should be recognized in their use. A recent publication by Vano et al.
[V3] indicated that, for old X-ray systems, a conversion coefficient of 0.21 mSv/(Gy cm2) should be
used and, for most recent systems with copper filtration, the coefficient should be 0.29 mSv/(Gy cm2).

Table C12. Typical radiation dose air-kerma area product, effective dose and conversion factors for interventional procedures in adults

Interventional procedure

KAP(Gy∙cm2) a

Effective dose(mSv) aConversion factor E/KAP(mSv/(Gy∙cm2)) a

15.3

0.19 b

MethodReference

CARDIAC
Belgium

PTCA

82

Multicentre study[B21]

Croatia

PTCA

55.2

Multicentre study[B34]

FrancePCI

56.8a

National study[G2]

Iran (Islamic Republic of)

PTCA

44.5

Two centre study[B2]

Ireland

PCI

78.3 (4.8–410.4)

All hospitals[D1]

Coronary angiography and PCI

91.5 (16–363.9)

All hospitals[D1]

Permanent pacemaker insertion

17.4 (0.45–171.9)

All hospitals[D1]

Russian Federation

Cardiology therapeutic

84±79 (14–377)

Multicentre study[S6]

SwedenAdult cardiovascular

University hospital[O5]

Switzerland

9.6±1.2

0.22

17±16 (3–75)
0.22

PCI

82 (3–283)

Multicentre study[A8]

Cardiac thermal ablation

128 (7–495)

Multicentre study[A8]

Coronary angiography and PCI

178 (27–487)

Multicentre study[A8]Electrophysiology and cardiac thermo ablation

348 (8–1 442)

Multicentre study

[A8]

PCI

57.6c

Multicentre study[S16]

Chronic total occlusion

143c

Multicentre study[S16]

Transcatheter aortic valve implantations

96.8

Multicentre study[S16]

Pacemaker implantation single chamber

2.4cMulticentre study[S16]

Pacemaker implantation double chamber

3.2

cMulticentre study[S16]

Cardiac resynchronization therapy pacemaker

14c

Multicentre study[S16]

Atrioventricular nodal re-entrant tachycardia

2.5cMulticentre study[S16]

Atrial flutter

6.6

cMulticentre study[S16]

Atrial fibrillation

6.6c

Multicentre study

[S16]

c

UNSCEAR 2020/2021 REPORTCountry or region

224

PCI: Prophylactic cranial irradiation; PTA: Percutaneous transluminal angioplasty; PTCA: Percutaneous transluminal coronary angioplasty; TIPS: Transjugular intrahepatic portosystemic shunt

Country or region

Interventional procedure

KAP(Gy∙cm2) a

Effective dose(mSv) aConversion factor E/KAP(mSv/(Gy∙cm2)) a

MethodReference

CEREBRAL
Indonesia

Cerebral arteriovenous malformations
embolization

211±113

One tertiary hospital[R1]

Coiling of cerebral aneurysm

315±147

One tertiary hospital[R1]

Intra-arterial thrombolysis

202±102

One tertiary hospital[R1]

Intra-arterial Nimodipine injection

97±87

One tertiary hospital[R1]

Juvenile nasopharyngeal angiofibroma
embolization

129±37

One tertiary hospital[R1]

Multicentre study[S6]

Multicentre study[A8]

Russian Federation

Cerebral therapeutic

145±104 (20–548)

Switzerland

Cerebral embolization

335 (24–1 345)

17±12 (12–49)

0.10

ABDOMINAL
20.3 (2–45.7)

0.14 (0.11–0.16)

One university
hospital[C14]

Abdominal PTAa

144.3 (6.7–281.9)

21.3 (0.7–41.8)

0.12 (0.10–0.15)

One university
hospital[C14]

Biliary drainagea

26.3 (3.2–236.3)

4 (0.5–47.4)

0.15 (0.14–0.19)

One university
hospital[C14]

Biliary stent insertiona

58.2 (13.5–289.2)

8.9 (1.9–41.6)

0.15 (0.13–0.17)

One university
hospital[C14]

Hepatic embolizationa

177.7 (98.1–346.5)

27 (14.8–58.5)

0.15 (0.15–0.18)

One university
hospital[C14]

Nephrostomya

29.6 (28.5–47.1)

7.5 (7.2–11.6)

0.25 (0.246–0.253)

One university
hospital

[C14]

TIPSa

337.6 (93.3–422.2)

49.6 (13.4–70.1)

0.15 (0.147–0.166)

One university
hospital[C14]

Russian Federation

Abdominal (hepatic, pancreatic) therapeutic

233±221 (16–855)

42±40 (3–154)

Multicentre study

[S6]

Spain

Transjugular hepatic biopsy

45

Multicentre study[R12]

Biliary drainage

30

Multicentre study[R12]

Hepatic chemoembolization

303

Multicentre study

[R12]

Italy

225

143.8 (17.8–303.3)

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

Abdominal embolizationa

Country or region

KAP(Gy∙cm2) a

Effective dose(mSv) aConversion factor E/KAP(mSv/(Gy∙cm2)) a

MethodReference
226

Biliary drainage

68.9

Multicentre study[V2]

Hepatic chemoembolization

218.3

Multicentre study[V2]

Hepatic embolization

463 (54–1 703)

Multicentre study[A8]

Biliary drainage and stent insertion

244 (5–1 375)

Multicentre study[A8]

One tertiary hospital[R1]

21.5 (0.1–326)

Multicentre study

[M2]

CHEST
Indonesia

Bronchial artery embolization

133±87PELVICFranceIliac endovascular revascularization

Indonesia

Renal artery embolization

161±111

One tertiary hospital[R1]

Spinal artery embolization

184±114

One tertiary hospital[R1]

Uterine artery embolization

193±100

One tertiary hospital[R1]

Multicentre study[S6]

Russian Federation

Pelvic (renal, urogenital)

Spain

Uterine fibroid embolization

214

Multicentre study[R12]

Colon endoprosthesis

169

Multicentre study[R12]

Femoropopliteal revascularization

119

Multicentre study[R12]

Iliac stent

170

Multicentre study[R12]

344 (36–1 122)

Multicentre study[A8]

Switzerland

Iliac dilatation

152±118 (32–562)

27±21 (6–101)

PERIPHERAL
Indonesia

ItalyaLower limb embolization

32±35

One tertiary hospital[R1]

Sclerotherapy

5.3±8.6

One tertiary hospital[R1]

Peripheral PTAb

52 (34.3–67)

One university
hospital[C14]

Empty cell indicates no data available.

bWith extra Cu (0.21); while without Cu (0.18).

c

Median values

12.7 (8.3–15.7)

0.23 (0.21–0.25)

UNSCEAR 2020/2021 REPORTSwitzerland

Interventional procedureANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

227

C33.
At least three procedures can be classified as PTCA procedures: namely, elective prophylactic
cranial irradiation (PCI), coronary angiography followed by ad hoc PCI and chronic total occlusion.
Variations between KAP values for PTCA procedures may be attributed to different categorization in acountry or even centres. In a multicentre study, the three classifications were separately analysed andthe median KAP values were found to be 62 Gy cm2 for ad hoc PCI and 36 Gy cm2 for elective PCI
while for chronic total occlusion, the KAP values were significantly higher [S16].
C34.
Omar et al. [O5] studied paediatric exposure during interventional procedures and provided
conversion coefficients for E/KAP according to ICRP Publication 103 [I11]. The reported coefficientswere 3.2, 2.2, 1.3, 0.8 and 0.4 mSv/Gy cm2 corresponding to the five age groups <0.5, 0.5–2.5, 2.5–7.5,
7.5–12.5 and 12.5–18 years, respectively.
C35.
Ubeda et al. [U1] provided conversion factors for diagnostic and therapeutic cardiac
procedures according to patient age and weight. For the four age bands (<1, 1–5, 5–10 and 10–16
years), the median values were 1.70, 0.89, 0.58 and 0.40 mSv/Gy cm2, respectively and for weightbands, the factors varied from 1.53 mSv/Gy cm2 for <10 kg to 0.33 mSv/Gy cm2 for 60 kg or more. The
conversion factors for paediatric interventions decreased with age.
C36.
A comprehensive review by Harbron et al. [H3] provided conversion factors according todifferent age or weight groups (table C13) and corresponding KAP values for paediatric cardiac
interventional procedures (table C14).
Table C13. Conversion factors for cardiac catheterization [H3]Age(years)
<1

1

5

10

15

30
a

Conversion factors E/KAP (mSv/(Gy cm2)) a[O6] b
2.72(3.4 kg)
1.01(9.2 kg)
0.49(19kg)
0.29(32.4 kg)
0.16
(56.3 kg)

[K4] b[S9] b

3.7/3.7

2.05/2.34

1.9/1.9

0.82/1.16

1/1

0.42/0.64

0.6/0.7

0.4/0.4

0.13(73.2 kg)

Empty cell indicates no data available.

b

According to ICRP 60 [I9].

cAccording to ICRP 103 [I11].

[D9][K6] c[B9] c3.61/3.31

2.34/2.2/4

3.5/3.5

1.8/1.4

2.19/2.17

1.27/1/4/2.7

1.6/2.6

0.9/0.7

0.91/0.87

0.8/1.3

0.24/0.38

0.71/0.65

0.5/0.8

0.13/0.22

0.41/0.39

0.3/0.4

0.10/0.16[A15] b

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UNSCEAR 2020/2021 REPORT

Table C14. Typical radiation doses in air-kerma area product for paediatric cardiac interventional
procedures by age and weight of patients [H3]Parameters

KAP (Gy cm2) for cardiac interventional procedures a
Patent ductus
arteriosus
occlusion

Atrial septal
defect/Patent
foramen ovale
occlusion

Reference

Pulmonary
valvuloplasty

Aorticvalvuloplasty

4 (8)b7

Age range (years)
<1

5

1–4

7

9 (22)b

10

19

5–9

13

14 (28)

b

16

21

10–15

33

39 (75)b

44

93

>15

96 (110)b89 (99)b

198

116

[G4]

Weight range (kg)

<6.5

2.1

6.5–14.5

1.4

1.8

14.5–25.5

2.8

0.7

25.5–43.5

4.3

1.1

>43.5

10.8

2.8

All weights

1.8

0.9

0–10

1.4

2.9

1.1

1.5

10–20

2.5

2.8

3.6

0.5

20–30

4.1

4.7

7.5

14.7

>30

20.9

12.7

50.9

44.5

All weights

2.5

5

1.6

3.4

5

2.4
4.7

5–12.5
12.5–25

2.6

7.3

25–45

5.6

16.2

45–65

30.6

>65

58.9

All weights

3.5

10.4

a

Empty cell indicates no data available.

b

Values in parentheses are taken from Verghese et al. [V5].

[B9]

[B22]

[G7]

4.1

11.2

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2.

229

Specific observations(a) Skin and eye lens dose
C37.
Skin dose in terms of cumulative doses were reported to the UNSCEAR Global Survey by
only two countries. Poland reported mean cumulative dose for head (cerebral) interventions of~500 mGy, while Lithuania reported a mean cumulative dose of 790 mGy for PTCA procedures.
Although data are scarce, high doses delivered to patient skin or eyes should not be ignored.
C38.
Skin reactions are a well-known complication of radiation exposure. In recent decades, they
have been recognized as a rare complication of interventional procedures [B8]. The frequency of majorradiation injuries is estimated to be between 1:10,000 and 1:1,000,000 procedures, however, the risk is
not known, mainly because it is assumed that these injuries are underreported [T8].
C39.
Perry et al. [P7] investigated patient doses, using a calculation software, for 3,300
interventional and neuro-interventional procedures. For interventional procedures, 2.7% were found to
exceed estimated skin dose of 5 Gy and all of them were performed in the abdominal/pelvic region.
However, patient follow-up revealed no subsequent injury. For neuro-interventional procedures, 5.1%
exceeded a skin dose of 5 Gy and 5 out of 49 patients reported temporary skin injuries [P7].
C40.
Dose metrics, such as peak skin dose, are now available on modern machines whilesophisticated software allows the presentation of real-time skin dose maps to facilitate dosemanagement [T8]. High radiation doses used during therapeutic interventional procedures are related totissue reactions. Brnic et al. [B34] recorded peak skin dose for PTCA procedures in four hospitals in
Croatia. In 8% of selected patients, peak skin dose exceeded the 2 Gy threshold for erythema. No skin
injuries were reported because a skin injury reporting system does not exist in Croatia; moreover, someskin injuries remain potentially unrecognized due to low clinical and risk awareness [B34].
C41.
The International Atomic Energy Agency (IAEA) conducted a multinational study in eight
countries in Asia. The peak skin dose was found to exceed 2 Gy for 20% of patients in this study [R4].
Peak skin doses for different therapeutic interventional procedures were reported in another multicentre
study in the Russian Federation by Sarycheva et al. [S6]. For cerebral and cardiology procedures, peakskin dose ranged 0.1–3.8 Gy and 0.1–2.6 Gy, respectively, but never exceeded the 2 Gy threshold for
abdominal and pelvic procedures. In another multinational prospective study by Tsapaki et al. [T7],peak skin dose was reported for diagnostic and therapeutic interventional procedures in 20 mainly lowincome countries (nine in Eastern Europe, five in Africa and six in Asia). Peak skin dose exceeded the
2 Gy threshold for 20% of patients, 4.6% were in the range of 4 to 6 Gy, and 2% in the range of 6 to
10 Gy. No skin injuries were reported; however, they could not be ruled out [S6]. In a tertiary carefacility in the United States with 7,500 interventional cardiology procedures per year, dose optimization
efforts reduced the number of procedures with skin doses over 5 Gy by 80% from 2007 to 2017 [T8].
C42.
Patient doses that may lead to eye lens reactions have been reported by Safari et al. [S1] forcerebral interventional procedures. The authors reported real-time eye lens doses during cerebral
angiography procedures. As patient eyes may be exposed to primary radiation, in vivo measurements
showed that eye lens dose may reach 2 Gy. In a study by Sanchez et al. [S5], 5 cases (16%) of the 31
therapeutic neuro-radiology procedures measured doses higher than 0.5 mGy to the left eye of thepatient with a maximum dose of 2 Gy. At these levels of radiation, the possibility of radiation induced
opacities or cataracts increases, especially in patients requiring several procedures. For the right eye,the dose measured was below 200 mGy, a value with a low probability to produce opacities.

230

UNSCEAR 2020/2021 REPORTC43.
KAP value alerts were also suggested as dose indicators for skin reactions. For PTCA
procedures, KAP values between 150 and 300 Gy cm2 may correspond to peak skin dose of 2 Gy. In a
multicentre study performed by Siiskonen et al. [S16] to establish European diagnostic reference levels,
it was found that more than 30% of transcatheter aortic valve implantation and chronic total occlusion
exceeded the 150 Gy cm2 threshold and approximately 2% exceeded 500 Gy cm2 [S16].
C44.
Although uncertainty in risks for tissue reactions remains, medical practitioners should bemade aware that the absorbed dose threshold may be as low as 0.5 Gy for circulatory disease to theheart or brain and also for cataract in the lens of the eye [I13]. During complex interventional
procedures, doses of this order can be reached, thus, emphasis should be put on optimization of theseprocedures [I13].
C45.
As tissue reactions may occur after interventional procedures due to high radiation dose, there
is a need to better report patient exposure during interventional procedures and record patient followup. Future evaluation for the most complex interventional procedures should include:−

Dose to the lens of the eyes (in neuro-interventional radiology);−

Dose to the cerebrovascular system (in neuro-interventional radiology);−

Dose to the cardiovascular system (in interventional cardiology).

(b) Influence of weighting factors of ICRP 60 and ICRP 103 to collective dose
C46.
The impact on effective doses for the different interventional procedures resulting from thechanges of the ICRP tissue weighting factors [I9, I11] were reported by Hart et al. [H5] in the United
Kingdom using a model developed by the National Radiological Protection Board (NRPB), resulting ina 2–3% decrease in the collective dose for conventional radiology, including dental, and for computed
tomography and a 12–13% increase for interventional radiology. This was reflected in an overall 2%
increase of the total collective dose due the ICRP weighting factors change (table C15).
Table C15. Impact of ICRP 60 and ICRP 103 tissue weighting factors on collective dose (man Sv) in
the United Kingdom in 2008 [H5]
Category of examination

Collective dose – EICRP60

Collective dose – EICRP103

Radiography (including dental)

4 695

4 799

Computed tomography

16 30216 723

Angiography (non-computed tomography)

1 213

1 187

Interventional (non-computed tomography)

2 037

1 985

Total

24 24724 694

C47.
In a recent study, Brambilla et al. [B30] estimated the effective dose and conversion factors
with the KAP for PTCA using the ICRP 103 tissue weighting factors [B30]. The results were comparedwith those previously published in the literature (table C16). Estimates of E/KAP conversion factors
based on ICRP 103 tissue weighting factors converged to a value of 0.33 mSv/Gy cm2, which wereabout 30% higher than previous estimates based on ICRP 60. Also, conversion coefficients depended
on individual installation variables, e.g., X-ray beam quality or protocol dependent (femoral or radialaccess), radiographic projections, phantom simulating the patient, the Monte Carlo code used for thesimulation. Many of the new interventional systems use high filtration in the X-ray beam, and theconversion factors (mSv/Gy cm2) may be higher than before [V3].

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

231

Table C16. Comparison of conversion coefficients calculated using ICRP 60 [I9] and ICRP 103 [I11]tissue weighting factors for coronary angiography and percutaneous coronary interventionsa

E/DAPPTCA (mSv/(Gy cm2))

Tissue weighting factors

References

0.13

ICRP 60 [I9]

[C13]

0.20

ICRP 60 [I9][C13] a0.25

ICRP 60 [I9]

[B36]

0.33

ICRP 103 [I11][B30]

Using the NRPB model with a mathematical phantom [H5].

3.

Impact of technology on patient doses

C48.
A study by Tsapaki et al. [T8] showed that the number of interventional procedures is steadily
increasing as these procedures are usually performed on an out-patient basis with shorter recovery time,
fewer complication risks for the patients and lower costs compared with open surgery. Moreover,fluoroscopy equipment with low-dose technology is expensive and not affordable for low-income
countries [T8].
C49.
Despite many efforts to reduce radiation dose, interventional procedures involve high patient
exposure that may even lead to tissue reactions. Considerable variation in patient exposure has beenreported in the literature and is related to patient factors (e.g., patient age, size, anatomy, co-morbidities),
operator factors (e.g., training, experience), technology (e.g., flat panel detectors, image intensifiers,
conventional or dedicated radiology table) and protocols used (e.g., fluoroscopy mode, cine mode,
frame rate, beam collimation) [B35, G2, G6, H3, I14].
C50.
Complexity of interventional procedures and its influence on patient irradiation has beenstudied for procedures performed for heart, liver and other body regions [B7, R12]. Complexity indicesinclude consideration of anatomical characteristics (e.g., vessel tortuosity, angulation), type oftreatment (stent, pre- or post-dilatation), type of injury (e.g., stenosis, obstruction), and puncture site
(e.g., ipsilateral, contralateral, bilateral). The higher the complexity index, the higher the patient
exposure. Using the complexity indices, procedures can be categorized as simple, medium andcomplex. Radiation doses for complex procedures were shown to reach up to 13 times those for simple
procedures [R12]. Regarding the management of skin injury risk, technology has facilitated radiationdose reporting and analysis by software tools allowing installed on the equipment, that provides realtime skin dose or dose management tools that collect and analyse offline the skin dose distribution [T8].
C51.
The most frequent interventional procedure is PTCA [U8] with a steady increase over time[N4]. However, in recent years, patients with arrhythmias, and with congenital and structural heartdisease can also be treated in the catheterization laboratory. Currently, a variety of new imaging
modalities that combine ionizing and non-ionizing radiation are available. Three-dimensional rotational
angiography provides real-time 3D volume and cross-sectional images to visualize complex cardiac
anatomy and navigation during the procedure and helps to reduce the amount of contrast media andradiation dose [K3, P5]. Electro anatomic systems enable conduct of complex electrophysiologicalprocedures with very low radiation doses [G1]. Transoesophageal echocardiography has allowed
ultrasonic image guidance for transcatheter procedures in septal and valvar structures. Special ultrasoundprobes allow application for neonates [P5].

232

UNSCEAR 2020/2021 REPORTC52.
New techniques require the use of various complex technologies in hybrid rooms with manydifferent professionals involved. Often, operators performing these interventional radiology procedures
have no training in radiation protection [T8]. Nevertheless, training efforts for operators lead to
reduction of patient radiation exposure and the risk of tissue reactions [F4, K11, S11].

V. DISTRIBUTIONS BY AGE AND SEX
A. UNSCEAR Global Survey data
C53.
Few countries provided data to the UNSCEAR Global Survey on age and sex distribution.
Figure C-III shows the analysis for age distribution for both sexes and all countries. The black line in
the figure represents the average age distribution for all procedures. The age distributions are similar,
with procedure frequencies peaking between the ages 65 and 74 years. Abdomen (TIPS) interventional
procedures showed also a peak for younger ages (30 years), while thoracic interventions seem to be
performed only on very young children.
C54.
Eight countries provided data on age and sex distribution in interventional radiology. Table C17
presents the sex distribution for different interventional procedures. Males appeared to undergo more
frequent (64%) interventional procedures than females (36%) for all interventional procedures apart from
cerebral interventions, where there was almost no difference between the two sexes.
Figure C-III. Age distribution by interventional radiological procedures
PTCA: Percutaneous transluminal coronary angioplasty; TIPS: Transjugular intrahepatic portosystemic shunt

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

233

Table C17. Distribution of male and female patients undergoing interventional procedures
PTCA: Percutaneous transluminal coronary angioplasty; TIPS: Transjugular intrahepatic portosystemic shunt
Procedure

Distribution (%)
Male

FemaleCerebral intervention

46

54

PTCA

72

28

Chest (pacemaker)

58

42

Thoracic intervention (other)

53

47

Abdomen (biliary and urinary)64

36

Abdomen (TIPS)

64

36

Abdomen (other)

72

28

Pelvic intervention

76

24

Limb intervention

62

38

Average

64

36

C55.
Since PTCA is the interventional radiology procedure contributing most to the collective dose,a more detailed analysis was attempted. Age and sex distribution for PTCA procedures are presented infigure C-IV and table C18, respectively. PTCA procedures are most frequent between the ages of 65
and 74 years. Males undergo these procedures more frequently than females in all countries that
submitted data to the UNSCEAR Global Survey.
Figure C-IV. Age distribution for PTCA procedures as reported to UNSCEAR Global Survey
PTCA: Percutaneous transluminal coronary angioplasty

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UNSCEAR 2020/2021 REPORT

Table C18. Distribution of male and female patients undergoing PTCA procedures as reported to
UNSCEAR Global Survey
PTCA: Percutaneous transluminal coronary angioplasty
Distribution (%)

Country

Male

FemaleAustralia

77

23

Belgium

73

27

Czech Republic

71

29

Denmark

75

25

Estonia61

39

Iceland76

24

Luxembourg

75

25

Poland

68

32

C56.
Age groups were classified in the UNSCEAR 2008 Report [U9] as 0–15, 16–39 and 40 years
and older. Table C19 shows a comparison of age distribution for PTCA procedures between the
UNSCEAR 2008 Report [U9] data and the UNSCEAR Global Survey for five countries. No country
reported significant numbers of PTCA procedures in the age group below 16 years. Table C19 alsopresents a comparison of sex distribution for PTCA procedures between the UNSCEAR 2008 Report[U9] and the current evaluation for the five countries. Men seemed to undergo PTCA procedures more
frequently than women in the Czech Republic, Romania and Spain, while data in the UNSCEAR 2008
Report [U9] showed that the distribution of procedure frequencies for the two sexes were similar.
Table C19. Comparison of age and sex distributions for PTCA procedures between UNSCEAR Global
Survey and UNSCEAR 2008 Report [U9]PTCA: Percutaneous transluminal coronary angioplasty
Country

Czech Republic

Iceland

Luxembourg

Romania

Spain

SourceAge distribution (%)

Sex distribution (%)

0–15 years

16–39
years

40+
years

Male

FemaleCurrent evaluation

0

1

99

71

29

UNSCEAR 2008

0

4

96

50

50

Current evaluation

0

0

99

76

24

UNSCEAR 2008

0

1

99

79

21

Current evaluation

0

2

98

75

25

UNSCEAR 2008

0

3

97

73

28

Current evaluation

0

2

98

60

40

UNSCEAR 2008

0

28

71

44

56

Current evaluation

0

2

98

76

24

UNSCEAR 2008

0

6

94

44

56

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

235

C57.
Figure C-V presents the age distribution for cerebral interventions. Age distribution differsfrom the mean of all interventional procedures, with patients between 55 and 64 years of age
undergoing cerebral interventional procedures more frequently. Table C20 shows no major differencesin frequencies between the two sexes (mean values for male 46% and for female 54%).
Figure C-V. Age distribution for cerebral interventional procedures

Table C20. Distribution of male and female patients undergoing head (cerebral) interventional
procedures as reported to UNSCEAR Global SurveyCountry

Distribution (%)
Male

FemaleAustralia

39

61

Belgium

34

66

Estonia53

47

Iceland63

37

Luxembourg

38

62

Poland

45

55

Mean

46

54

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UNSCEAR 2020/2021 REPORT

B. Literature review data
C58.
The age distribution of patients undergoing interventional procedures is rarely reported in theliterature. In Italy, Peruzzo Cornetto et al. [P8] reported that 12% of the interventional cardiology
procedures were performed on patients younger than 60 years of age, 56% for patients aged between 60
and 79 years and 32% for patients older than 80 years. No significant differences were found in thefrequency distributions for cardiac interventional procedures when age and sex were compared.
C59.
In Luxembourg, Shannoun et al. [S12] showed that the distribution of interventional
procedures shifted to older patients, with about 80% of the interventions performed on patients between
50 and 80 years. Further, interventional procedures (cardiac or vascular) were more frequent for men
than women [S12]. In Romania, a study by Girjoaba and Cucu [G5] reported that most patients
undergoing interventional procedures were over 40 years old. For the age group 16–40, for all
angiographic procedures (diagnostic and therapeutic), 20% were cerebral angiographies and 18% pelvic
angiographies. In Spain [S4], twice as many men as women underwent interventional cardiac
procedures, with average ages of 69 and 73 years, respectively. Only 2% of patients were between theage of 20 and 40 and 30% of patients between 40 and 60 (figure C-VI).
Figure C-VI. Age and sex distribution of interventional cardiac procedures for a sample of 4,301
procedures performed in Spain (2014–2015) [S4]C60.
In Costa Rica, a study by Ubeda et al. focused on the estimation of the collective dose to the
paediatric population deriving from interventional cardiac procedures (diagnostic and therapeutic) [U2].
The distribution of the dose according to age showed that 65% of the collective dose due tointerventions were performed to patients between 10 and 16 years. Nonetheless, most paediatricinterventional procedures in this study were performed on children aged less than 5 years.

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

237

C61.
In Kenya [K13], Korir et al. reported that 20% of the cardiac interventional procedures were
performed on children; a number higher than that reported by Tsapaki et al. [T7]. The authors statedthat in high-income countries 10% of the interventional procedures were performed on children while
in low-income countries it was only 5%. An explanation might be that the majority of the procedures in
Kenya were diagnostic ones [K13]. In the United States, although paediatric procedures were notincluded in the estimation for interventional procedures, it was reported that less than 1% of cardiac
procedures were performed on children [N1].
C62.
In a multinational study by Tsapaki et al. [T7], the annual diagnostic and therapeuticinterventional procedures in 20—mostly low-income—countries (nine Eastern European, five Africanand six Asian) were reported for patients under the age of 15 years; however, without giving moredetails on patient age distribution. The percentage of children of the total annual activity varied
enormously between participating hospitals (0.2–35.4%), while three of the 20 countries did not reportpaediatric procedures in the general hospitals chosen for the study. Of the procedures in three paediatrichospitals (two from Africa and one from Europe), 2–36% were therapeutic procedures.
C63.
Rehani et al. [R4] reported information on paediatric cardiology procedures in nine Asian
countries (table C21). In all countries except Sri Lanka (32%) the contribution of paediatric procedures
was lower than 10%.
Table C21. Contribution of paediatric diagnostic and therapeutic interventional cardiology
procedures in nine countries in Asia [R4]Country

Fraction of paediatric interventional procedures toall interventional procedures (%)

Kuwait4.8

Lebanon

0.5

Malaysia

2.7

Pakistan

9.1

Philippines

4

Qatar

2.5

Sri Lanka

32

Syria

1.5

Thailand

0.2

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UNSCEAR 2020/2021 REPORT

VI. STAFF AND DEVICES
C64.
The numbers of professionals performing interventional procedures per million of population
submitted to the UNSCEAR Global Survey are presented in table C22. There are three main groups ofstaff: interventional radiologists, interventional cardiologists and other physicians. The data on thenumber of professionals show large variations between countries. This has a direct impact on thenumber of interventional procedures performed in a country. However, the recording of professionals
differs from country to country. The number of interventional radiologists in Finland includes both
radiologists and cardiologists. The unusually high number of interventional cardiologists in Sweden is
explained by the fact that the reported number of interventional cardiologists includes all licensed
cardiologists of whom an unknown fraction is actually involved in cardiac interventional radiology. The
United Kingdom counted interventional staff with general practitioners and radiologists, while in
Luxembourg, interventional radiology is not an official medical specialty.
C65.
Interventional procedures, according to the UNSCEAR Global Survey [U11], are performed
with the same equipment as angiography examinations. Thus, the term “angiography systems” is usedalso for the systems used for interventional procedures. The detailed numbers of angiography systems
and devices per million of population are presented in table B29 and the number of angiographysystems by country is displayed as frequencies per million population in figure C-VII. Data on
angiography systems from the Republic of Korea and Switzerland are included in fluoroscopy.
Figure C-VII. Number of angiography systems by country per million population as reported in
UNSCEAR Global Survey

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

239

Table C22. Number of interventional staff as absolute numbers and as frequencies per million
population as reported to UNSCEAR Global SurveyCountry

Number

Per million
population

Number

Per million
population

487

12

300

BelgiumBrazilArgentina
Australia

50

2

Other physicians conducting
interventional procedures a
Number

Per million
population

13

4 010

169

504

45

1 174

105

651

3

Belarus

90

9

9

1

8

1

Cyprus

2

2

27

28

100

105

Czech Republic

137

13

361

34

83

8

Estonia

3

2

15

11

Finland

244

44
1 100

17

FranceGreece

208

19

514

47

Hungary

306

31

49

4.9

164

16.7

Indonesia

2

0.008

7

0.03

3

0.01

Lithuania

37

13

63

22

Luxembourg

20

35

Malaysia

13

0.4
5

0.05

266

14

3

92

500

59

99

11

Philippines

14

0.1

Romania

166

8

Russian Federation

301

15

847

6

San Marino

2

61

Slovenia

20

10

30

15

Spain

305

7

411

9

1 700

170

SwedenaInterventional
cardiologists a

Interventional
radiologists a

Switzerland

250

30

170

20

Thailand

145

2

270

4

United Arab Emirates

38

4

76

8

United Kingdom

433

7

660

10

United States

2 967

9

3 255

10

Empty cell indicates no data available.

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UNSCEAR 2020/2021 REPORTC66.
The European Coordination Committee of the Radiological, Electromedical and Healthcare IT
Industry published the density data (number of systems in use per million population) for angiographyequipment in 2016 [C11]. Accordingly, angiography equipment uses X-rays in combination with acontrast agent (chemical substances used to enhance specific structures in images) in order to visualize
blood vessels, particularly the coronary arteries. In this sense, angiography equipment is used for bothangiography and interventional procedures. In Western Europe, the average number of X-ray
angiography systems per million population decreased from 15.6 in 2013 to 13.4 in 2016 while inCentral and Eastern Europe, the average number showed a slight increase [C11], which might impact
the number of procedures performed in the future because of the wider access to this technology.
C67.
The age profile of equipment has deteriorated slightly in Western Europe since 2013, butshowed a marked improvement in Central and Eastern Europe [C11]. The X-ray angiographyequipment age profile has also deteriorated in the Russian Federation, with the percentage of “six years
and older” systems increasing from 32% to 40%. In China, X-ray angiography systems which are “fiveyears old or less” have increased to 65% since 2013.
C68.
Maurel et al. [M2] performed a multicentre study in France for iliac interventional proceduresand found a decrease in the number of procedures performed in a radiological suite with a simultaneous
increase for the procedures performed in endovascular theatre, mainly due to improvement andmodernization of equipment. Advanced imaging techniques offer better image quality and allow
operators to perform more complex procedures (e.g., for obese patients, steep angles). However, it is
not necessarily related to lower radiation doses [M2]. In Slovenia, Zontar et al. [Z1] observed that 80%of the interventional procedures are performed in university medical centres while the rest are
performed in two general hospitals and one private clinic. In Switzerland, Samara et al. [S2] studied thesituation and found that more than 50% of the interventional procedures are performed in university
hospitals and rarely in private institutes (8%).

VII. TRENDS
C69.
Although the UNSCEAR Global Survey did not cover all interventional procedures in detail, it
is noted that the number of interventional procedures performed outside the traditional radiological or
cardiological suite is increasing. A clear demonstration of this trend was observed in Spain. The total
number of procedures was 400,853, including vascular surgery, with a global distribution of 45%
diagnostic and 55% therapeutic interventional procedures.
C70.
As described in the UNSCEAR 2008 Report [U9], interventional procedures dramaticallyincreased in frequency, principally because of the numerous benefits for the patient, the significant
development in equipment and the number of trained interventionists. A steady increase was observedin PTCA procedures by, on average, 6.7% across 29 countries in Europe between 1990 and 2003 [U9].
C71.

Four countries presented data on trends in exposure from interventional radiology:(a) In Luxembourg, Shannoun et al. [S12] observed an increase of the effective dose per caput
from 0.05 mSv in 1994 to 0.12 mSv in 2002 for therapeutic interventional procedures;(b) In Norway, Borretzen et al. [B25] calculated an increase of 12% between 1993 and 2002 forinterventional procedures;ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

241(c) In Switzerland, Samara et al. [S2] reported an increase of interventional procedures between
1998 and 2008. The number of therapeutic interventional procedures per 1,000 population
increased from 3.8 in 1998 to 6 per 1,000 population in 2008. The effective dose per caput also
increased from 0.04 to 0.07 mSv. A very small increase in therapeutic interventional procedures
was observed between 2008 and 2013 but this can be attributed to the different methodology
applied [L2, S2];(d) In the United Kingdom, Hart et al. [H5], observed an increase in interventional proceduresfrom 0.9 to 1.4% between 1998 and 2008.
C72.
A multinational study by Tsapaki et al. [T7] found the number of interventional procedures tohave increased between 2004 and 2007. The rate of increase ranged between 6 and 196% (table C23).
Three of the 11 countries had more than a 100% increase, another four between 50 and 91%, and theremaining four had a 6 to 24% increase. One country showed the largest rate of increase (196%)
because five of the 13 catheterization laboratories for which data on workload were provided did notexist in 2004.
C73.
In contrast, Smith-Bindman et al. [S18] indicated a decrease of angiography/fluoroscopy
procedures in the United States between 1996 and 2010 in a retrospective analysis of electronic recordsof members of six large integrated health systems from different regions in the country. As thegrouping of the examinations includes both angiography and fluoroscopy procedures, it cannot be
concluded whether the number of therapeutic interventional procedures is, indeed, declining or thenumber of fluoroscopy procedures is declining.
C74.
In Germany between 2007 and 2014, the mean effective dose per procedure decreased forangiography and interventional procedures, as reported by Nekolla et al. [N3]. However, the effective
dose per caput remained practically constant with a mean effective dose of around 0.3 mSv per caput
indicating that the number of interventions increased.
Table C23. Comparison of annual number of interventional procedures between 2004–2007 [T7]Country

2004

2007

Increase (%)

Algeria

3 839

4 641

21

Armenia

496

1 062

114

Bosnia and Herzegovina

579

1 100

90

Bulgaria

5 910

7 357

24

Croatia

1 795

2 975

74

Kenya

192

337

76

Lebanon

2 050

4 627

126

Lithuania

25 78127 440

6

Pakistan

9 613

28 475

196

Syria

4 067

4 565

12

Thailand

2 059

3 736

81

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UNSCEAR 2020/2021 REPORT

VIII. SUMMARY
C75.
A detailed survey of interventional procedure practice across the world was undertaken and thesubmitted data has been analysed to estimate for each country the frequency of procedures and therelated effective dose per procedures.
C76.
The uncertainty in each of these estimations arises from a number of sources. Some countries
conducted a survey of a limited number of clinics and hospitals and then extrapolated the data to thewhole of the country. This can lead to an over- or underestimate of the true number depending on how
representative the sample sites were of the whole country. Secondly, the reporting of interventional
procedures differs from country to country, which can further lead to an over- or underestimation of thefrequencies of the different examinations and procedures. Thirdly, as far as it concerns information onradiation dose per procedures, data are often not available from national surveys. Uncertainties onradiation doses depend on several factors such as technology, operator training and procedurecomplexity. Effective doses were estimated using conversion coefficients from ICRP 60 [I9] asconversion coefficients calculated with ICRP 103 [I11] for all interventional procedures were scarce.
This needs to be taken into account for any future comparisons.
C77.
Despite these limitations, the UNSCEAR Global Survey results indicate that the frequency ofinterventional procedures has significantly increased worldwide. Although interventional procedures
are less frequent than radiography or computed tomography examinations, they generally involve highradiation doses and make a significant contribution to the collective dose (8% of the collective dose,
figure II). The mean frequency of interventional procedures for the current survey is 13 procedures per
1,000 population in high-income countries, while ~2 procedures per 1,000 population were reported in
the UNSCEAR 2008 Report [U9]. The collective dose was estimated at 41,000 man Sv in the
UNSCEAR 2008 Report [U9], whereas in this evaluation it is estimated to be 334,000 man Sv. The age
distribution of interventional procedures peaks between the ages of 65 and 74 years. Male patients
undergo cardiac interventions at around two to three times the rate of female patients.
C78.
Frequencies of interventional radiology procedures per 1,000 population vary considerably
between countries, according to data in the literature and in the UNSCEAR Global Survey. PTCA
remains the most frequent interventional procedure. However, with increasing numbers ofinterventional procedures performed outside hospital cardiology and radiology departments, future
surveys should broaden the types of procedures included for better global estimations.
C79.
Interventional radiology procedures in future surveys should include procedures with both
diagnostic and therapeutic intent since procedures frequently begin as diagnostic but may move tointervention as dictated by the needs of the particular case. Moreover, the data from this survey
indicated that the number of procedures performed outside radiology and cardiology departments isincreasing. Radiological equipment used for interventional procedures should be identified asinterventional X-ray systems. This standardization of terminology for interventional procedures infuture surveys would improve both data collection and the robustness of data analysis.
C80.
Finally, the high radiation doses associated with interventional procedures may lead to tissue
reactions. As interventional procedures become more complex, higher radiation doses should be
expected. Future surveys should include estimations of radiation dose to the skin, the lens of the eyes,
and the cerebrovascular and cardiovascular systems.

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION243

APPENDIX D. LEVELS AND TRENDS OF EXPOSURE IN NUCLEAR
MEDICINE

I. INTRODUCTION
D1.
Nuclear medicine is primarily a functional imaging modality that uses radioactively labelledradiopharmaceuticals to localize and visualize specific body tissues, including pathological lesions. The
images are obtained by detecting the gamma rays emitted by the patient, using a gamma camera, or by
detecting the annihilation photons using positron emission tomography (PET). Tomographic images
can be obtained from a series of images, using a gamma camera rotated around the patient, in aprocedure known as single photon emission computed tomography (SPECT).
D2.
Although the images provide extensive functional information, they often present poor
anatomic structural information. The advantages of combining nuclear medicine images withradiological images to improve the anatomic localization of abnormalities initially led to softwarebased registration methods to superimpose images from multiple modalities acquired independently ofeach other. This was effective for rigid objects such as the skull (and thus for the brain), but less so forother parts of the body. Alternatives to software-based fusion are now available throughinstrumentation that combines two complementary imaging techniques within a single gantry, anapproach called “hybrid imaging” combining computed tomography to SPECT/CT or PET/CT, which
can acquire co-registered structural and functional information within a single procedure. Thesesystems allow simultaneous separate imaging by the two modalities while the patient is in exactly thesame position on the imaging table. The data are complementary, allowing computed tomography toaccurately localize functional abnormalities and SPECT or PET to highlight areas of abnormal
metabolism. The computed tomography images also facilitate accurate attenuation correction of thenuclear medicine images. More recently, hybrid systems using magnetic resonance imaging PET/MRI
have become available commercially, which eliminates the additional radiation exposure from thecomputed tomography scan.
D3.
The first SPECT/CT systems featured a four-row computed tomography detector unit with arotation time of 23 seconds. The first combined SPECT/CT system that incorporated a fully-clinicalcomputed tomography system was released in 2004 [B15]. Initially, this system was equipped with a
two-slice computed tomography scanner but was later available with six or 16-slice computed
tomography scanners. Similar systems quickly became available from all major medical imaging
manufacturers and are now available with 64-slice computed tomography systems with automatic
exposure control and iterative reconstruction to optimize resolution and to minimize radiation dose. A
SPECT based on cadmium zinc telluride detector was introduced specifically for cardiac applications in2009 [B15]. The main benefit of such detectors - over standard scintillator detectors -is the much higher
energy resolution providing improved discrimination of scattered photons, thus improving the image
contrast and potentially leading to a reduction in administered radiopharmaceutical activity. SPECT/CT
systems are increasingly replacing stand-alone SPECT systems although a number of nuclear medicine
procedures, particularly dynamic studies, require only the gamma camera images, so SPECT-onlysystems will remain clinically useful.

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UNSCEAR 2020/2021 REPORT

D4.
The first prototype PET/CT became operational in 1998, incorporating a single-slice spiralcomputed tomography and a rotating bismuth germanate based PET system. Torso imaging using theprototype PET/CT took one hour or more [B16]. The first commercial PET/CT was announced in early
2001. Over the years, PET/CT designs have evolved following the advances in CT and PET
instrumentation. The introduction of lutetium oxyorthosilicate and gadolinium silicate based PET
systems, which could be operated with short coincidence time windows (4.5–6 ns) and higher lowerenergy thresholds (400–450 keV) compared with 10–12 ns and 350 keV for a typical bismuth
germanate based PET system, significantly improved whole-body image quality. The availability of fast
scintillators with high stopping power such as lutetium oxyorthosilicate and lutetium-yttrium
oxyorthosilicate enabled time-of-flight PET to become commercially viable in 2006. Time-of-flight
PET has the potential to improve image quality or reduce image acquisition time. This gain is related tothe object size, and the largest gain can be expected in heavy patients, which suffer most from poor
image quality [B16]. The axial field of view has been also extended, typically, 16 cm to over 20 cm
permitting shortened acquisition times and thus improving patient throughput or reducing theadministered activity for the same acquisition time. PET systems in which the axial field of view isextended to cover the full length of the patient are currently undergoing clinical trials [C8]. Such PET
systems have the potential of a 40-fold gain in sensitivity permitting whole-body PET acquisitions in
15–30 seconds, compared to 10–20 minutes. Alternatively, the administered activity could be reduced by
40% for the same acquisition time, with a corresponding reduction in patient dose.
D5.
The development of combined PET/MRI systems started in the late 1990s. However, it was
not until 2006 that the first simultaneous MRI and PET images of a human brain were acquired,involving a PET detector ring inside a 3 Tesla MRI system [B14]. Paediatric imaging is a key
application for PET/MRI because of the lack of the additional ionizing radiation dose from thecomputed tomography component and also because of the advantage/convenience of a single
examination providing both functional and anatomic information. The role of PET/MRI in routine
clinical practice is still being established. In 2015, approximately 70 systems were reported worldwide,
and it has remained primarily a research tool [B4]. Neurological applications stand to benefit greatly
from PET/MRI investigations. Similarly, many cardiac studies have suggested that PET/MRI may
replace PET/CT [B4].
D6.
Radiopharmaceuticals labelled with 99mTc remain the mainstay of clinical nuclear medicine.
About 80% of radiopharmaceuticals in clinical use are still 99mTc based, particularly for cardiac,skeletal, renal and lung imaging. The most commonly used PET radiopharmaceutical is 18F-fluoro-2-Ddeoxyglucose, (18F-FDG), a radiolabelled analogue of glucose. FDG PET/CT has now become the main
imaging modality in diagnosis, staging, restaging and prognostication of many cancers. However, thedevelopment in nuclear medicine imaging technology has been matched by the introduction of new
radiopharmaceuticals into routine clinical use. Many of these are labelled peptides which have beenused for both diagnosis and treatment of disease, leading to the term “theranostics” [B11].
D7.
Radioiodine (131I) has been used throughout the world for decades in the treatment of both
hyperthyroidism and thyroid cancer. In some countries this remains the only radionuclide therapy inuse; nevertheless, nuclear medicine therapy continues to evolve at an increasing rate. Radiolabelledsomatostatin analogues were first reported in 1989 and, a few years later, targeted radionuclide therapyof neuroendocrine tumours with somatostatin analogues followed. The somatostatin conjugates
DOTATOC and DOTATATE, labelled with 111In and 68Ga for SPECT and PET imaging, respectively,
and with 90Y and 177Lu for targeted radionuclide therapy, are routinely used in many hospitals [M12].
The 68Ga and 177Lu combination has more recently been extended to advanced prostate cancer treatmentusing labelled, prostate-specific membrane antigen. Lutetium-177 has the advantage of a 208 keVgamma emission enabling quantitative SPECT/CT imaging of the distribution of the radiopharmaceutical leading to calculation of the internal dose distribution within an accuracy of ± 10%. Modern

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

245

gamma cameras offer software packages for calculating patient-specific radionuclide treatment
planning for routine clinical usage. Certain radionuclide therapies, such as selective internal radiation
therapy using 90Y-microspheres, require the radiopharmaceutical to be administered under fluoroscopic
control. This will necessitate an additional radiation dose from the angiography.
D8.
Radionuclides have been used for many years in the treatment of widespread bone metastases.
This treatment has involved 89Sr-chloride or 153Sm-ethylene diamine tetramethylene phosphonate and,more recently, 223Ra-dichloride. The latter radionuclide is an alpha-emitter which was initially used in
the treatment of metastatic prostate cancer and, more recently, of metastatic breast cancer, withconfirmed patient survival benefits. Other therapies involving alpha-emitting radionuclides are
currently under development.

II. RECAPITULATION OF PREVIOUS UNSCEAR REPORTS
D9.
The Committee estimated the worldwide total number of nuclear medicine procedures for
1985–1990, 1991–1996 and 1997–2007 [U5, U6, U9] to be 24, 32.5 and 32.7 million annually,corresponding to annual frequencies of 4.5, 5.6 and 5.1 per 1,000 population, respectively. The 1997–
2007 global total estimate of procedures was distributed among the health-care levels of the model asfollows: (a) 89% in HCL I countries (at a mean rate of 22 per 1,000 population); (b) 10% in HCL II
countries (1.0 per 1,000 population); and (c) <1% collectively in countries of HCLs III and IV (<0.05
per 1,000 population) [U5, U6, U9].
D10.
There were significant variations in the national frequencies between countries with the same
health-care level. An overall decrease in the average value for HCL I countries observed in 1997–2007
was likely to be due to underreporting during that survey period. Several cases of clear increases in thenumbers of procedures were seen in some countries, and some other countries (e.g., Canada and UnitedStates) that had previously reported high values did not report to the current UNSCEAR Global Survey.
D11.
The global annual collective effective dose for 1997–2007 was estimated to be about
202,000 man Sv, which equated with an average per caput effective dose of 0.031 mSv [U9]. Theseestimates were comparable with the values for 1991–1996 (150,000 man Sv and 0.03 mSv) [U5] and1985–1990 (160,000 man Sv and 0.03 mSv) [U6]. The distribution of collective dose among the healthcare levels in 2007 was: (a) 92% in HCL I countries (giving a mean per caput dose of 0.12 mSv),(b) 8% in HCL II countries (corresponding to 0.005 mSv per caput) and (c) <1% in HCL III and IV
countries (0.00005 mSv per caput). Globally, practice was dominated by bone, cardiovascular andthyroid procedures, with the last being particularly important in HCL III and IV countries.
D12.
Overall, during 1997–2007 the use of diagnostic nuclear medicine procedures remained minor
in comparison with the use of diagnostic radiological examinations. The annual numbers of nuclear
medicine procedures and their associated collective doses were only 0.9 and 5.1%, respectively, of
those for diagnostic radiological examinations. However, the mean dose per diagnostic procedure waslarger for nuclear medicine (6.0 mSv) than for diagnostic radiology (1.3 mSv) [U9].
D13.
The use of therapeutic nuclear medicine varied significantly between countries. Global annual
numbers of radiopharmaceutical therapeutic treatments were broadly estimated from the limited
national survey data using a global model. The uncertainties in these data were known to be significant.
The worldwide total number of treatments for 1997–2007 was estimated to be about 0.87 million,
corresponding to an average frequency of 0.14 treatment per 1,000 population [U9]. Radionuclide
therapy during the period was less common than teletherapy (4.7 million treatments) but was similar in
number to brachytherapy (0.43 million treatments).

246

UNSCEAR 2020/2021 REPORTIII. FREQUENCIES OF NUCLEAR MEDICINE PROCEDURES
D14.
This section presents information on trends in the frequencies of nuclear medicine procedures
resulting from the submissions to the UNSCEAR Global Survey (2009-2018) also summarized inelectronic attachment D-1. Furthermore, the data were supplemented with information from reviews of
the published literature.

A. UNSCEAR Global Survey data
D15.
Altogether, 49 countries submitted data for nuclear medicine procedures (diagnostic/
therapeutic) to the UNSCEAR Global Survey. Unfortunately, the data for many countries wereincomplete and did not provide a good basis for the evaluation of population doses, i.e., collective
effective doses and per caput effective doses. Data on the frequencies of examinations (i.e., annual
numbers of procedures) were more complete; however, the submitted dose data (administered activity
and dose length product (DLP) values, or typical effective doses) were scarce. Some countries
submitted total frequencies but did not provide numbers for the individual procedures, while othercountries provided procedure frequencies but no data on doses. Of the 49 country submissions,
36 provided individual procedure frequencies, 33 provided average administered activities, 8 provided
DLP values for the computed tomography component of SPECT/CT procedures and 11 provided DLP
values for the computed tomography component of PET/CT procedures.
D16.
Table D1 shows the frequency of nuclear medicine procedures and separately for PET
procedures. However, few countries submitted only the total number of procedures without differentiation
between SPECT and PET procedures. Further, the table includes a comparison with the frequency of
nuclear medicine procedures reported in the UNSCEAR 2008 Report [U9], although a number ofcountries did not provide data for the earlier survey, no comparison was possible for these countries.
D17.
The frequency of nuclear medicine procedures per 1,000 population has fallen significantly ina number of European countries, while increasing significantly in others. The average change infrequency of nuclear medicine procedures since the UNSCEAR 2008 Report [U9] was +14%
(excluding the very high percentage change recorded in Belarus) although the population-weighted
change was only 3%. Seven of the 49 countries did not have access to PET. Table D1 also shows that
PET procedures accounted for an average of 18% of nuclear medicine procedures (range 1–67%) in the
countries that reported such data.
D18.
Figure D-I displays the frequency of all nuclear medicine diagnostic procedures from table D1
in graphical form, which clearly highlights the very wide variation in study frequency across the world,with the highest frequencies occurring in Western Europe, Canada and the United States.

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

247

Table D1. Comparison of diagnostic nuclear medicine procedures frequency per 1,000 population
reported to UNSCEAR Global Survey with UNSCEAR 2008 Report [U9]
PET: Positron emission tomography
Procedures (frequency per 1 000 population) a,b
Country

Current evaluation

UNSCEAR
2008

Changecompared to
UNSCEAR 2008
Report (%)

Proportion of
PET to total
(%)

Total

PET

Argentina

15.4

2.1

Australia

26.2

3.4

Bangladesh

0.1

0.007

Belgium

44.8

4Brazil

4.9

0.1

2

Bulgaria

3.7

1.3

34

Belarus120Canada

39.4

2.5

6

China

1.8

0.4

20

Croatia

9.9

1.8

Cyprus5.7

0Czech Republic

15.4

2.6

Denmark

30.2

8.2

Estonia

4.2

1

2

106

23

Finland

7.5

1.6

7.7

−3

22

France

16.8

3.6

14

20

21

Germany

31.8

1.7

46.7

−32

5

Greece

13.3

0.5

16.7

−20

4

Hungary

48.9

4.1

17.9

173

8

Iceland

4.3

0

14.1

−69

0

Iran (Islamic Republic of)

7.6

0.04

Italy

40

Japan

13.6

4.5

Lebanon

4.6

2.1

45

Lithuania

7.1

0.6

8

Luxembourg

24.1

4.2

Madagascar

0.01

0

0

Malaysia

1.5

0.9

60

Montenegro

3

0

0

Netherlands

25.2

4.6

Niger

0.04

0

14
19

38

13
6

52.8

0.4

8.6

−15

2 900

15

9

0

18
0

12.6

22

17
27

1

10.2

34.5

24.3

33

−30

4

33

17

18
0

248

UNSCEAR 2020/2021 REPORT

Procedures (frequency per 1 000 population) a,b
Country

Current evaluation

UNSCEAR
2008

Changecompared to
UNSCEAR 2008
Report (%)

Proportion of
PET to total
(%)

Total

PET

North Macedonia

1.5

1

4

−61

67

Norway

8.4

2.3

10.9

−23

27

Pakistan

0.9

0.04

5

Philippines

0.2

0.02

10

Poland

5.4

1.2

3

79

23

Romania

1.9

0.5

2.8

−33

25

Russian Federation

3.4

0.2

6

Saudi Arabia

3.2

0.003

0

Spain

13.4

1.4

Sudan

0.2

Sweden

10.3

2.1

10.8

−5

21

Switzerland

16.7

5

11.7

43

30

Thailand

0.9

0.05

5

United Arab Emirates

1.5

0.3

21

Ukraine

6.8

0.1

1

United Kingdom

9.9

2.4

24

United States

42.1

5.8

14

16.9

−20

10
0

a

Values are rounded; however extended precision has been preserved to illustrate differences.

b

Zero values are indicated when available; otherwise, cells have been kept empty.

D19.
Table D2 presents the frequency of each major procedure performed using gamma cameras
and/or SPECT systems in the 35 countries that provided this information. It shows that in the UnitedStates cardiovascular procedures account for more than 50% of all annual SPECT procedures with arate of 19.9 per 1,000 population, almost 3 times greater than the next highest, Greece, with 7 per 1,000
population. The distribution in the United States differs widely from that in other countries, where often
skeletal procedures have the highest frequency.

Table D2. Frequency per 1,000 population for nuclear medicine diagnostic procedures (using either gamma camera or SPECT) as reported to UNSCEAR Global Survey
SPECT: Single-photon emission computed tomography
Nuclear medicine procedures (frequency per 1 000 population) a,b
Country

Total cCardiovascular

Endocrine

Gastrointestinal

Renal

Infection

NervoussystemArgentina

13.3

4.9

0.3

0.5

0.2

0.05

0.1

Australia

22.8

5.3

2.1

0.9

0.7

0.3

0.3

Brazil

4.8

3.3

0.2

0.03

0.4

Bulgaria

2.5

0.06

0.3

0.01

0.1

Belarus

12

China

1.5

0.07

0.3

0.2

Croatia

8.1

1.2

1.7

0.8

Cyprus

5.7

2.1

1.1

0.9

Czech Republic

12.8

2.1

0.3

0.07

1

0.1

0.2

Denmark

21.9

4

3

0.1

3.6

0.07

Estonia

3.2

0.4

0.6

0.01

0.2

0.01

Finland

5.9

1

0.04

0.03

France

13.3

4.2

1

Germany

30.1

6.6

13.6

Greece

12.8

7

0.8

Iceland

4.3

0.3

0.5

Japan

9.1

2.1

Lithuania

6.6

0.9

1

0.01

0.5

Luxembourg

19.9

2.7

5.8

0.1

0.6

Montenegro

3

0.6

0.01

0.3

Niger

0.04

0.01

0.004

0.001

0.002

Norway

6.1

1.5

0.8

0.07

0.8

0.002

Oncology

Pulmonary

Skeletal

Lymphatics

0.05

5.9

1.2

0.2

2.3

10

0.8

0.001

0.04

0.07

0.6

0.07

0.03

0.05

0.2

1.7

0.07

1.8

8.3

0.8
2.8

0.2

1.4

0.07

3.4

4.7

0.9

0.3

0.02

2.1

2.8

0.5

0.09

0.6

0.1

0.5

0.09

0.3

0.2

1

0.4

1.9

0.03

0.2

0.5

0.8

5.3

0.04

0.7

0.06

0.2

0.7

0.9

7.1

0.7

0.05

0.06

0.02

0.3

3.4

0.4

0.03

0.4

0.7

0.4

3.2

1.6

0.3

0.2

3.3

0.4

0.3

0.006

0.1

2.7

0.3

0.5

0.1

0.9

7.9

0.6

0.03

1.4

0.05

0.03

0.09

0.009
0.5

0.8

0.2

1.2

0.06

249

0.03

0.006

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

0.3

0.1

0.07

Total c

Cardiovascular

Endocrine

Gastrointestinal

Renal

Philippines

0.2

0.005

0.04

0.001

0.02

Poland

4.2

0.6

1.2

0.04

0.6

0.02

Romania

1.4

0.1

0.2

0.03

0.09

0.002

RussianFederation

3.1

0.2

0.4

0.1

0.9

0.02

Spain

12.1

2.6

1.3

0.7

Sudan

0.2

0.001

0.09

0.001

0.03

Sweden

8.2

2.8

0.6

0.1

0.8

0.03

0.2

0.8

1.1

1.7

Switzerland

11.7

1.7

0.3

0.006

0.4

0.8

0.09

0.02

0.6

2.5

Thailand

0.8

0.1

0.1

0.02

0.04

0.002

0.002

0.009

0.01

0.4

0.01

United ArabEmirates

1.2

0.3

0.3

0.04

0.2

0.01

0.003

0.03

0.03

0.3

0.007

Ukraine

6.7

0.003

0.004

1.2

UnitedKingdom

7.6

2

0.4

0.4

0.7

0.04

0.2

0.5

0.6

2.6

United States

36.3

19.9

1.8

2.9

1.1

0.9

0.6

1.2

2.1

a

0.8

Empty cell indicates no data available.

cValues as reported; may not equal sum of all categories.

NervoussystemOncology

Pulmonary

Skeletal

Lymphatics

0.1

0.4

0.4

0.1

1.5

0.2

0.03

0.9

0.06

0.02

0.08

1.5

0.3

0.4

5.6
0.06

0.7

Values are rounded; however extended precision has been preserved to illustrate differences.

b

Infection

0.006

0.001

0.4
5.2

UNSCEAR 2020/2021 REPORTCountry

250

Nuclear medicine procedures (frequency per 1 000 population) a,b

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

251

Figure D-I. Annual frequency of diagnostic nuclear medicine procedures per 1,000 population asreported to UNSCEAR Global Survey

D20.
Twenty-nine countries provided information on their PET activities. The annual frequency of
PET procedures per 1,000 population is given in table D3, which clearly shows that oncology remains
the principal use of PET imaging accounting for more than 90% of all PET procedures in mostcountries.
Table D3. Frequency of PET procedures per 1,000 population as reported to UNSCEAR Global Survey
PET: Positron emission tomography
PET procedures (frequency per 1 000 population) a,b
Country

Total cCardiovascular

Argentina

2.1

Australia

3.4

Belgium

4

Brazil0.1

0.02

Bulgaria

1.3

0.001

Croatia

1.8

0.21

Czech Republic

2.6

Denmark

8.2

Estonia1

Infection

NervoussystemOncology

Skeletal

2.1
0.05

3.3
4

0.80

0.1
0.003

0.02

1.3
1.6

0.45

2.6

0.04

0.09

6.6

0.01

0.01

0.9

0.07

252

UNSCEAR 2020/2021 REPORTPET procedures (frequency per 1 000 population) a,b
CountryaTotal cCardiovascular

Infection

NervoussystemOncology

Skeletal

Finland

1.6

0.09

0.14

1.1

0.04

France

3.6

Germany

1.7

Greece

0.5

Japan

4.5

0.03

0.14

4.4

Lithuania

0.6

0.005

0.01

0.6

Luxembourg

4.2

Norway2.3

Philippines

0.02

Poland

1.2

Romania

0.5

Russian Federation

0.2

Spain

1.4

Sweden2.1

Switzerland

5

Thailand0.05

United Arab Emirates

0.3

Ukraine0.1

United Kingdom

2.4

0.04

0.04

2.3

United States

5.8

0.23

0.17

5.4

3.6
0.05

0.16

1.5
0.5

4.2
0.008

0.17

2.1
0.02

0.002

0.001

0.0002

1.2

0.004

0.5
0.01

0.2
1.4

0.02

0.001

0.40

1.6

0.22

5
0.005
0.004

0.04
0.3

0.008

0.08

Values are rounded; however extended precision has been preserved to illustrate differences.

b

Empty cell indicates no data available.

cValues as reported; may not equal sum of all categories.

D21.
The numbers of therapy procedures using radionuclide were reported by 41 countries and arepresented in table D4 and figure D-II as a frequency per 100,000 population. Thirty-three countries
provided detailed numbers for the major procedures of radionuclide therapy. The treatment of thyroid
disease using 131I accounts for an average of 74% of all radionuclide therapy procedures. Proteinreceptor radionuclide therapy using either 90Y or 177Lu-octreotide for neuroendocrine tumours and177
Lu-PSMA for prostate cancer, is now becoming routinely available in many countries and represents
approximately 5% of the reported procedures. Germany reported a very high frequency of radiosynovectomy procedures (87/100,000), more than 10 times higher than any other country.

Table D4. Frequency of radionuclide therapy procedures per 100,000 population as reported to UNSCEAR Global Survey
PRRT: Protein-receptor radionuclide therapy; SIRT: Selective internal radiation therapy; MIBG: Meta-iodobenzylguanidine
Radionuclide therapy procedures (frequency per 100 000 population) a,b
Alltherapy c

Thyroidbenign (131I)

Thyroidcancer (131I)

Bone mets(89Sr, 153Sm,223Ra)

Argentina

39.8

0.7

24.6

2.2

Australia

17.2

13.5

2.5

0.2

0.01

Bangladesh

25

Belgium

49.5

40.3

3.3

3.1

0.18

Brazil

8.6

6.1

1.7

0.06

Bulgaria

3.2

1.5

0.8

0.2

Belarus17.8

Canada

32.2

China

43.4

15.3

3.1

Cyprus

26.8

6.8

20

Czech Republic

18.5

3.8

11.2

Denmark

38.2

30.7

0.8

Estonia

56.3

29.7

32.3

0.2

2.5

Finland

34.2

17.2

10.4

0.2

2

Germany

135.5

25.6

17.1

Greece

27.5

2.8

21.9

1.6

Hungary

15.3

Iceland

32.3

7.6

6.1

18.6

Iran (Islamic Republic of)

3.9

Iraq

4.7

Japan

8.3

3.9

2.9

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

Lebanon

17.1

1.7

0.8

253

Country

PRRT(90Y, 177Lu)

0.1

Polycythaemia
(32P)

0.005

Radiosynovectomy(90Y,153Sm 169Er,186Re)

0.2

SIRT
(90Y)

MIBG
(131I)

2.2

0.7

0.8

2.6
0.5

0.03

3.4

0.02

0.1
4.1

0.9
0.2
4.2

0.2

2.7

87.1

0.3

0.8

2
0.03

a

All
therapy c

Thyroidbenign (131I)

Thyroidcancer (131I)

Bone mets(89Sr, 153Sm,223Ra)

Lithuania

16.2

11.9

Luxembourg

32.7

31.6

Malaysia

2.8

Netherlands

14.5

5.4

5.5

1.7

1.9

0.1

Norway

26.6

12.5

3.5

10.2

0.04

0

Pakistan

2.2

Philippines

0.3

0.1

0.2

Poland

54.4

33.9

7.2

1.9

0.2

Romania

12

2.2

9.9

Russian Federation

20.5

4.8

13.7

2.1

Spain

37.2

18.2

13.6

0.8

1.6

Sudan

4.4

0.7

0.1

Sweden

45.3

16.3

5.7

19.4

0.9

Switzerland

38.1

7.1

10.7

Thailand

21.8

13

8.8

0.002

United Arab Emirates

5.1

2.2

2.8

0.04

Ukraine

5.8

4.3

0.5

0.3

0.1

United Kingdom

13.3

5.6

2.1

3.7

1

0.1

United States

16.7

15

1.7

Empty cell indicates no data available.

cValues as reported; may not equal sum of all categories.

Polycythaemia(32P)

Radiosynovectomy(90Y,153Sm 169Er,186Re)

SIRT
(90Y)

MIBG
(131I)

0.2

0.1

2.1
1.1

Values are rounded; however extended precision has been preserved to illustrate differences.

b

PRRT(90Y, 177Lu)

7.6

0.1

0.1
3

0.8

0.002

0.05

0.08

0.03

1.7

4.3

0.1

0.003

0.01

0.01

0.04
0.5
0.2

0.5

0.1

UNSCEAR 2020/2021 REPORTCountry

254

Radionuclide therapy procedures (frequency per 100 000 population) a,b

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

255

Figure D-II. Frequency of therapeutic nuclear medicine procedures per 100,000 population asreported to UNSCEAR Global Survey

B. Literature review data on nuclear medicine procedures andcontribution to population dose
D22.
The population dose from nuclear medicine examinations was reported in 17 of the reviewed
nuclear medicine articles, corresponding to 15 individual countries and one region (Europe). These
articles are summarized in table D5. Eleven of the articles provided an analysis of the contribution to
the population dose from the major nuclear medicine procedures.
D23.
The frequency of nuclear medicine procedures in relation to the total number of medical
imaging procedures was relatively small, ranging from 0.2% to 6.2% (average 1.9%). However, thecontribution to the collective effective dose was higher (0.7% to 26%, average 8.6%), resulting in an
average effective dose of 0.12 mSv per caput. Although these articles reported on national surveys
which had been conducted over a 13-year period (2002–2015), there was no correlation between per
caput effective dose and year of study. Rather, the wide range of reported doses (0.0025 mSv in
Romania to 0.77 mSv in the United States) reflected both the differences in the frequency of procedures
and also the differences in the type of procedures performed. This was particularly evident in the
Republic of Korea, where PET/CT procedures contributed 56% of the 0.15 mSv per caput effective
dose, with cardiac studies contributing only 12%, and in the United States, where the 0.77 mSv per
caput effective dose was primarily due to the very high proportion of cardiac studies (85%).

256

UNSCEAR 2020/2021 REPORT

D24.
If the six non-European countries are considered separately, the per caput effective dose was
0.23 mSv, compared with the average of 0.07 mSv for the eleven European papers (nine countries).
This latter value is in keeping with the value of 0.05 mSv reported for 36 European countries in theEuropean Commission Dose Data Med 2 project (EC DDM 2) [E5].
D25.
A comparison of the procedure frequency from the literature and from the UNSCEAR Global
Survey is given in table D6 for nine countries included in table D5, which have provided data for thecurrent survey. Countries in which the data was collected in more recent years, such as Croatia and theRussian Federation, showed good agreement with the current survey. While the values from some of
the European countries showed a reduction in nuclear medicine procedures of up to 33%, othercountries, such as Romania (110%) and Bulgaria (42%), reveal a significant increase. Values from
Australia increased by 30% while those from the United States decreased by 32%, reflecting changes intechnology, radiopharmaceuticals and referral patterns in each country.
D26.
The EC DDM 2 project [E5] provided comprehensive information on 36 European countries
regarding frequencies and radiation dose of diagnostic radiological examinations and nuclear medicine
procedures. The information presented in the EC DDM 2 project is based on national surveys carriedout between 2007 and 2010.
D27.
Overall, the total frequency of diagnostic nuclear medicine procedures in Europe was 14 per
1,000 population. Table D7 shows the average European frequencies for the major nuclear medicine
procedures. The total frequencies are somewhat lower than the HCL I countries’ mean frequency of 19
per 1,000 population for 1997–2007, according to the UNSCEAR 2008 Report [U9].
D28.
The frequency of paediatric procedures was reported for France by Étard et al. [E11] for 2010.
Nuclear medicine procedures accounted for 0.3% of all paediatric medical imaging leading to a percaput effective dose of 0.006 mSv. Bone scans (48%) and renal scans (36%) were the main procedures
performed in the children.
D29.
The frequency per 1,000 population of nuclear medicine diagnostic procedures continues tovary widely across the world. In many countries, the annual frequency of procedures remained below
10 per 1,000 population while the highest recorded frequency in the current survey was almost 50 per
1,000 population in Hungary.

Table D5. Frequency of nuclear medicine procedures per 1,000 population and corresponding contribution to collective effective dose from nuclear medicine proceduresin published literature (2006–2018)
CT: Computed tomography; PET: Positron emission tomography
Year
Country or region

Frequency ofprocedures per
1 000 population a,b

Proportion of all
diagnostic
procedures (%)a,b

Contribution tocollective
effective dose(%)a,b

Per caput
effectivedose(mSv) a,b

6.2

10

0.11

Australia

2010

20.2

Bulgaria

2007

2.6

Croatia2015

9.8

Europe (EC DDM 2)

2010

FinlandReferenceContributions to collective effective dose (%)a,b
Bone

Lung

Thyroid33

Cardiac

Renal

PET/CT

42

[H6]

0.01
1.5

[K14]

0.03

28

1.3

12.3

19

14

5

0.06

39

1.6

6.6

28

2009

7.7

6.3

0.03

France

2007

19

10.2

0.13

23

Iran (Islamic Republic of)

2014

22.6

0.12

6.6

Ireland

2010

6.5

32

Italy (Emilia-Romagna region)

2006

Italy (Aosta Valley Region)

2011

Republic of Korea

1.6

2.4

36

2.1

77

6

3

0.3

[K15]

16

[B20, E5]

8

[B19]

31

[E10]

0.5

[T1]

54

[O1]

9

0.05

2

10

0.10

[C12]

10.4

1.8

5.9

0.12

[A2]

2013

12.8

0.3

9.7

0.15

Luxembourg

2002

36

7.6

0.15

Portugal

2010

8

0.08

22

3

48

Romania

2012

0.9

0.3

0.7

0.003

52

9

3

Russian Federation

2015

3.5

0.2

1.7

0.009

Taiwan, China

2008

13.6

1.8

13.6

0.10

36

1

1.7

28

3.7

9.1

[C6]

United States

2006

62.2

4.5

26

0.77

9

1

0.2

85

0.3

1.8

[M10]

Values are rounded; however significant figures have been preserved.

b

Empty cell indicates no data available.

7

12

1

26

1

a

1.5

3

2.1

5.6

56

[L3]
[S12]

2

10

[T3]

33

[G5]
[B6]

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

6

257

258

UNSCEAR 2020/2021 REPORT

Table D6. Comparison of frequency of nuclear medicine procedures per 1,000 population asreported to UNSCEAR Global Survey with published study values
Country

Frequency of procedures per 1 000 population

Study year

Reference

20.2

2010

[H6]

3.7

2.6

2007

[K14]

Croatia

9.9

9.8

2015

[K15]

Finland

7.5

7.7

2009

[B19]

France

16.8

19

2007

[E10]

Luxembourg

24.1

36

2002

[S12]

Romania

1.9

0.9

2012

[G5]

Russian Federation

3.4

3.5

2015

[B6]

United States

42.1

62.2

2006

[M10]

Current evaluation

Study value

Australia

26.2

Bulgaria

Table D7. Average frequency of nuclear medicine procedures per 1,000 population in Europe asreported to the EC DDM 2 project [E5]
PET: Positron emissions tomography
Nuclear medicine procedure

Average frequencies per 1 000 populationfor 36 European countries

Bone scan (99m Tc)

3.5 (N=35)

Heart total

2.6 (N=33)

Lung perfusion (99m Tc)

0.5 (N=35)

Thyroid total

1.8 (N=35)

Renal total

0.8 (N=35)

Brain

0.1 (N=28)PET

0.4 (N=17)

PET and diagnostic computed tomography

0.4 (N=15)

IV. ADMINISTERED ACTIVITY AND EFFECTIVE DOSE FOR
NUCLEAR MEDICINE PROCEDURES
A. UNSCEAR Global Survey data
D30.
Table D8 summarizes the average administered activities for each major nuclear medicine
procedure imaged with a gamma camera and/or a SPECT system as reported to the UNSCEAR Global
Survey, and table D9 presents similar data for PET procedures.

Table D8. Administered activities for nuclear medicine procedures using gamma camera or SPECT as reported to UNSCEAR Global Survey
SPECT: Single-photon emission computed tomography
Administered activities per procedure (MBq) a
Nervous system

Skeletal

Cardiovascular

Lung

Endocrine

Gastrointestinal

Country
99m

Tc

I

123

99m

Tc

99m

Tc

1 140

1 088

925

Australia

775

890

1 202

Belgium

709

765

742

Brazil964

1 008

Bulgaria

642

170

Canada

740

111

99m

Tc

99m

Tc

I

123

99m

Tc

99m

Tc

Oncology

99m

Tc

185

370

189

185

140

132

327

169

376

110

207

165

45

173

838

149

222

373

190

603

680

119

293

105

188

366

925

1 184

400

370

19

300

925

740

833

633

560

666

574

183

786

832

Denmark

170

668

Estonia

228
176

191

China
Croatia

855

111

CyprusCzech Republic

Finland

747

692

France

93

Tc

Ga

99m

211

53

67

636

450
74

74

230

400

194

102

207

189

616

158

164

95

683

417

101

216

99

747

266

591

537

103

299

173

110

99

330

240

150

9

113

370

296

400

75

120

70

Greece

665

195

660

670

105

180

150

Iceland

740

180

680

740

125

326

Japan

611

179

714

848

740

1 500

92

74

488

500

100

336

108

141

186

205

220

723
423

222

100

150

200

145

800
170

248

740

552

370

744

190
100

218

555

74

148

450

200

370

74

259

650

20

Tc

182

140

180

263

200

97

740

690

99m

Lymphatics

1 147

155

Germany

Lithuania

74

I

123

185

680

Lebanon

14

In

111

Infection
inflammation

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

Argentina

Tl

201

Genitourinary

260

Administered activities per procedure (MBq) a
Skeletal

Cardiovascular

Lung

Endocrine

Gastrointestinal

99m

Tc

I

123

Tc

99m

Tc

Tl

201

99m

Tc

99m

Tc

Luxembourg

820

740

99

Malaysia

784

340

375

Niger

700

1 110

691

554

1 037

1 087

740

800

660

Norway771

185

Philippines
Poland740

Romania
Russian Federation

560

225

Saudi Arabia

a

99m

110

I

123

99m

Tc

Genitourinary
99m

Tc

78

209

296

185

110

185

185

198

324

129

88

78

345

403

198

370

80

185

120

850

222

167

689

500

490

150

100

130

130

150

750

1 110

150

370

185

185

222

95

734

186

771

764

208

449

Sweden

812

185

530

486

120

106

Thailand

601

710

647

98

436

243

212

114

United ArabEmirates

740

714

1 076

112

320

323

204

158

Ukraine

740

750

550

550

100

Average

746

730

764

208

232

Empty cell indicates no data available.

183

103

99m

Tc

97

In

111

Infection
inflammation
I

123

153

99m

Tc

Ga

67

Lymphatics
99m

Tc

1 030

38

647

79

67

Spain

196

Oncology

470
370

171

156

79

170

372
196

74

230

846

719
537

100
128

217

171

489

166

239

668

243

64

UNSCEAR 2020/2021 REPORT

Nervous system
Country

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

261

Table D9. Administered activities for nuclear medicine procedures using PET system as reported to
UNSCEAR Global Survey
PET: Positron emission tomography
Administered activities (MBq) a
Country

Oncology
F

18a

Cardiovascular
Ga

68

F

18

O

15

Skeletal

NervoussystemInfection inflammation

F

18

F

18

18

Argentina

344

Australia

262

Belgium

277

Brazil320278

Bulgaria

300

1 036

Canada

444

740

370

China

370

296

296

Croatia230

230

Czech Republic

309

187

Denmark

295

295

Estonia

291

200

181

Finland

311

241

211

France300

Germany

350

250

200

Greece

345

Japan

202

Lithuania

340

Luxembourg

296

Malaysia

327

Norway232

Philippines

280

Poland400

Romania291

Russian Federation

280

Spain

336

Sweden

274

153

408

Thailand

318

187

555

Ukraine350

Average309

Empty cell indicates no data available.

182

370

260

291

410

F

740

240

234
329

304
220

186

300

300

490

360

203

299
296
350

260

399

482

264

279

455

262

UNSCEAR 2020/2021 REPORT

D31.
Table D10 presents DLP values for the computed tomography component of SPECT/CT
studies, and table D12 presents similar data for PET/CT studies. Table D11 shows the percentage of
SPECT procedures that used co-registered computed tomography acquired with a SPECT/CT system.
This latter value varies significantly both between countries and between different procedures. No
country reported using SPECT/CT for renal procedures.
Table D10. Dose length product for nuclear medicine procedures using computed tomography
components as reported to UNSCEAR Global Survey
Dose length product per procedure (mGy cm) a
Country

Cardio-Nervous

Skeletal

Australia

94

210

66

Czech
Republic

220

150

80

Estonia
Finlandvascular

115

Endo-

Gastro-Oncol-

Infection -crine

intestinal

ogy

inflammation

204

213

180

229

628
84

136

30

Iceland

a

Lung

15

11

81

50

73

389

Malaysia

120

30

RussianFederation

210

32

265

270

12

18
130

Thailand

114

242

17

198

225

409

409

Average

128

227

41

132

234

211

175

100

165

Empty cell indicates no data available.

Table D11. Nuclear medicine procedures using computed tomography component as reported to
UNSCEAR Global Survey
CT: Computed tomography; SPECT: Single-photon emission computed tomography
Percentage of nuclear medicine procedures using CT component of SPECT/CT (%) aCountry

Skeletal

Australia

80

66

71

Czech
Republic

50

30

70

Estonia
Finlanda

Cardio-Nervousvascular

Lung
23

Endo-

Gastro-Oncol-

Infection

crine

intestinal

ogy

inflammation

19

6

72

62

95
35

100

8

27

11

40

Iceland

10

100

100

42

RussianFederation

20

5

1

10

10

13
32

Thailand

50

6

55

13

8

1

53

Average

54

34

55

30

24

6

54

Empty cell indicates no data available.

100

81

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

263

Table D12. Dose length product for nuclear medicine procedures using PET/CT system as reported
to UNSCEAR Global Survey
CT: Computed tomography; PET: Positron emission tomography
Dose length product per procedure (mGy cm) a
Country

Oncology

Cardiovascular

Australia

591

Brazil837

838

Bulgaria

365

558

China

715

715

Czech Republic

450

Estonia

570

Finland189

NervoussystemInfection inflammation

152
1 056

715

59
110

LithuaniaaSkeletal

689

542

45

411

Malaysia

1 261

1 114

Russian Federation

800

700

Thailand

479

259

Average

626

555

817

322

542

Empty cell indicates no data available.

D32.
Table D13 presents the effective dose corresponding to those procedures listed in table D8and, similarly, table D14 shows the corresponding effective doses for the PET procedures listed intable D9. Table D15 summarizes the effective dose from the computed tomography component of the
SPECT/CT procedures and table D16 presents the computed tomography dose for the PET/CT
procedures for those countries which recorded this information.
D33.
The effective dose was calculated using the dose coefficients published in the user manual for
the UNSCEAR Global Survey [U11]. The coefficients for the radiopharmaceutical dose (effective dosein mSv per administered activity in MBq) were primarily taken from ICRP publication 128 [I15]. For
the computed tomography dose the E/DLP coefficients (mSv/mGy cm) were adopted from theEuropean guidance on estimating population doses from medical X-ray procedures [E3]. A number ofcountries did not provide the administered activity and/or the DLP, but directly provided an estimate of
the effective dose. These are indicated in italics in tables D13–D16.

Effective dose (mSv) a,b
NervoussystemCountry

99mTc

Skeletal

123I

Cardiovascular

99mTc

99mTc

201Tl

Lung

Endocrine

123I

Gastrointestinal

Genitourinary

99mTc

99mTc

99mTc

99mTc

2

3.3

0.9

1.6

2.9

1.8

0.8

1.2

Oncology

99mTc

Argentina

8.8

5.3

8.3

Australia

7.2

4.4

10.8

19.6

1.5

4.3

Belgium

6.6

3.7

6.7

15.4

2.3

2.1

Brazil

7.4

4.9

7.5

1.6

2.9

3.5

1.7

Bulgaria

6

8.5

3

6.1

1.3

3.8

1.4

1.3

3.3

Canada

6.9

5.6

4.5

10.7

4.4

4.8

0.2

2.1

8.3

3.6

7.5

3.1

5

9.6

China
Croatia8

5.6

CyprusCzech Republic

3.3
6.9

13

3.1

16.3

11In

123I

2.6

1

67Ga

99mTc

10.4

7

21.1

0.06

18.2

4.1

29.6

2.4
1.7

1.3

1

10.4

2.5

5.2

1.4

14.3

2.3

2.5

8.5

3.3

4.3

1.7

2.1

0.7

Estonia

11.4

3.3

3.8

1.1

2.8

0.7

0.4

3.5

8.8

2.9

4.8

1.1

3.9

38.1

0.8

0.9

4.3

3.3

9

2.6

2

2

Finland

6.4

15.9

France

6.9

Germany

5.7

9

3.2

3.6

10.5

1.3

0.9

Greece

6.2

9.8

3.2

4

14.7

2

2

Iceland

6.9

9

3.3

6.7

1.4

4.2

Japan

5.7

8.9

3.5

7.6

3.6

13.5

1

1

2.4

4.5

1.1

4.4

15.1

4.4

2.4

6.1

Denmark

13.2

99mTc

5

7.5

5.3

67Ga

22.2

3.9

Lithuania

131I

0.9

3.8

2.4

1.4

11.9

8

0.7

8.1

1.4

7.8

8.8
17

1.7

8.1

9.4

81.4

8.2

1.3
0.7

1.3

1

7.7

1.4

Lymph
atics

12.6

9.1

LebanonInfection
inflammation

4.8

0.09

UNSCEAR 2020/2021 REPORTSPECT: Single photon emission computed tomography. Reported values are in italics

264

Table D13. Effective dose (mSv) calculated from administered radiopharmaceutical for nuclear medicine procedures using gamma camera or SPECT system as reported to
UNSCEAR Global Survey

Effective dose (mSv) a,b
Country

Nervoussystem99mTc

Cardiovascular

Luxembourg

4

6.7

1.3

Malaysia

3.8

3.1

4.9

Niger

3.4

10

3.4

5

5.1

9.8

3.6

7.2

3.2

9.3

Philippines
Poland6.9

Romania
4.3

11.3

Saudi Arabia

99mTc

Genitourinary

99mTc

99mTc

0.7

1.5

Oncology

99mTc

3.3

2.4

24.2

3.1

1.3

5.9

2.2

4.2

28.3

0.4

0.5

0.9

4.5

6.9

1

4.1

1

1.7

0.6

7.7

2.4

2.2

9

2.5

4.4

1.7

1.3

28.6

3.7

10

1.7

4.8

40.7

15.4

13.3

Spain

6.8

9.3

3.8

6.9

2.3

5.8

Sweden

7.6

9.3

2.6

3.6

1.3

1.4

Thailand

4.6

3.5

4.5

13.7

4.8

United ArabEmirates

6.9

3.5

9.7

15.6

Ukraine

6.9

3.7

5

Average

6.6

3.6

6.8

9.2

123I

Gastrointestinal

14.4

1.2

11In

9.2

3.2

3.6

0.8

3.5

4.2

3.5

1.1

6.1

1.3

2.3

3

Empty cell indicates no data available.

67Ga

99mTc

5

0.09

3.2

0.09

0.09

0.6

Values are rounded; however extended precision has been preserved to illustrate differences.

99mTc

0.7

0.2

b

67Ga

Lymph
atics

0.08

8.4

a

131I

8.3

1.2
2.5

123I

Infection
inflammation

4.1
2.5

6.5

23

9.3
4.8

17.1

9

5.9

0.7
24.5

2.9

1.1

3.7

9

3.1

7.6

19.7

6.8

21.8

0.08

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

RussianFederation

99mTc

Endocrine

99mTc

7.2

201Tl

Lung

99mTc

Norway123I

Skeletal

265

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UNSCEAR 2020/2021 REPORT

Table D14. Effective doses calculated from administered radiopharmaceutical for nuclear medicine
procedures using PET as reported to UNSCEAR Global Survey
PET: Positron emission tomography. Reported values are in italics
Effective dose (mSv) a
Country

Oncology
F

18

Cardiovascular
Ga

68

F

18

O

15

Skeletal

NervoussystemInfection inflammation

F

18

F

18

18

Argentina

6.5

Australia

5

Belgium

5.3

Brazil6.1

5.3

Bulgaria

5.7

19.7

Canada

8.4

14.1

China

7

5.6

Croatia

4.4

4.4

Czech Republic

5.9

3.2

Denmark

5.6

5

Estonia

5.5

3.4

3.4

Finland

5.9

4.1

4

France

5.7

Germany

6.7

4.3

3.8

Greece

6.6

Japan

3.8

Lithuania

6.5

Luxembourg

5.6

Malaysia

6.2

Norway4.4

Philippines

5.3

Poland7.6

Romania

5.5

Russian Federation

5.3

Spain

6.4

Sweden5.2

3.9

Thailand6

3.7

United Arab Emirates

5.4

9.5

Ukraine

6.7

Average

5.9

aEmpty cell indicates no data available.

4.7

2.9

10.5

F

7

5.5

4.4

6.3

14.1
5.6

1

4.6

4.4
5.6

5.2
4.2

3.5

5.7

5.7

9.3

3

0.45

3.5

5.7
5.6

7

0.61

6.3
6.7

5.9

7.6

0.7

4.7

4.7

8.6

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

267

Table D15. Effective dose from computed tomography component for nuclear medicine procedures
using SPECT/CT system as reported to UNSCEAR Global Survey
CT: Computed tomography; SPECT: Single photon emission computed tomography. Reported values are initalics
Effective dose (mSv) a
Country

Nervous

Skeletal

Cardiovascular2

2

Argentina
Australia

0.2

2.9

0.9

Czech Republic

0.5

2.1

1.1

Estonia
FinlandPulmonary

Gastrointestinal

Onco
logy

inflammation

1.6

3.2

3.1

3.4

8.8
0.2

0.4

Iceland

2
0.2

0.2

0.7

1

Malaysia

1.7

0.4

RussianFederation

2.9

0.4

3.7

0.2

0.3
2

Thailand

0.2

3.4

2.3

2.8

6.1

6.1

Average

0.3

3

1

1.9

3.2

2.7

a

Infection -

1.5

2.5

Empty cell indicates no data available.

Table D16. Effective dose from computed tomography component for nuclear medicine procedures
using PET/CT system as reported to UNSCEAR Global Survey
CT: Computed tomography; PET: Positron emission tomography. Reported values in are italics
Effective dose (mSv) a
Country

Oncology
F

18

Cardiovascular
Ga

68

F

18

Argentina

16.3

Australia

8.9

Brazil12.6

11.7

Bulgaria

5.5

7.8

China

10.7

10

Czech Republic

6.8

Estonia

8.5

Finland

2.8

O

15

Nervoussystem

F

18

18

9

F

F

18

15.8
1.5
0.1

3.4

Infection inflammation

0.3

1.5

0.9

Lithuania

10.3

8.1

0.1

6.2

Malaysia

18.9

Russian Federation

12

Thailand

7.2

7.2

Average

10

6.5

a

Skeletal

Empty cell indicates no data available.

16.7
1.5
0.5
7.8

0.9

12.3

0.7

8.1

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UNSCEAR 2020/2021 REPORT

B. Literature review data
D34.
Most estimates of the effective dose in the reviewed literature used the organ absorbed dosecoefficients and effective dose coefficients (mSv/MBq) from ICRP publication 128 [I15]. Thispublication is a compendium comprising ICRP publication 53 [I8] and all subsequent addenda, and
ICRP 60 [I9] for the tissue weighting factors, which were derived using the Medical Internal Radiation
Dosimetry (MIRD) hermaphrodite mathematic phantom originally developed at Oak Ridge National
Laboratory [C15]. The ICRP published revised tissue weighting factors in 2007 [I11] and developed
ICRP computational voxel adult male and female models [I12] and will be publishing a revision of
ICRP 128 [I15] using these voxel models and the updated tissue weighting factors.
D35.
The administered activity for each nuclear medicine procedure varies considerably both withina country and between countries. Table D17 includes the mean activities of published national surveys
from both European [E5] and other countries.

Table D17. Mean activity administered to adult patients per nuclear medicine diagnostic procedures as reported in literature
PET: Positron emissions tomography
Mean activity administered per procedure (MBq) a
Country or region

Year

Bone
99m

Tc

Myocardial
Tl

201

99m

Whole
body PET
Tc

F

Tc

18

99m

1 000

Australia

2010

800

120

1 300

370

Belgium

2015–2017

750

110

1 360

270

Bulgaria

2007

740

1 100

2013

570

925

2013

Cardiac blood
pool

Inflammation
Ga

633

Europe(EC DDM 2)

2010

662

Finland2007

700

Germany

2004

Tc

99m

Tc

67

99m

200

300

200

800

200

200

740

185

Hepatobiliary
99m

Tc

200

Thyroid
99m

99

1 240

230

1 250

351

696

1 100

370

750

Tc

200

[H6]

165

[F2]

150

100

[K14]

158

74

[A13]

77

120

154

855

98

[K15]

177

178

157

704

158

[E5]

300

150

150

[K14]

370

[B32]

661

74

970

Iran (Islamic
Republic of)

2014

628

89

1 324

141

Italy (region)

2011

942

144

1 150

354

Japan

2016

110

1 007

Russian Federation

2013

160

Taiwan, China

2008

888

United Kingdom

2016

800

United States

2006

1 110

185

370
800

400

1 500

740

1 480

352

[B33]

145

740

162

92

[T1]

362

971

210

163

[A2]
[O7]

300
89

Reference[A14]

2007–2008

740

111

235

132

222

296

130
740

205

[Z2]

185

[C6]
[I7]

1 100

150

370

185

740

185

370

[M9]
[D6]

269

Empty cell indicates no data available.

99m

Brain

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

2015

a

Tc

Lung

285

Croatia

2013

Renal

270

UNSCEAR 2020/2021 REPORT

D36.
For all EC DDM 2 [E5] 36 countries, the mean effective dose was 0.054 mSv per caput andnuclear medicine contributed 5% to the total per caput effective dose for all medical imaging
procedures of 1.10 mSv. The total average annual effective dose per caput ranged from 0.002 mSv in
Romania to 0.162 mSv in Greece. Although large national differences in the average population dosefrom nuclear medicine procedures have been observed, the seven procedures (TOP 7) shown intable D18 were identified as being among the highest contributors to the collective effective dose in all
EC DDM 2 [E5] countries, accounting for 91.3% of the total per caput effective dose.
Table D18. Procedures identified as highest contributors to total collective effective dose of nuclear
medicine procedures in EC DDM 2 project (TOP 7) [E5]
CT: Computed tomography; FDG: Fluoro-2-D-deoxyglucose; MIBI: Methoxy isobutyl isonitrile;
MAA: Macroaggregated albumin; PET: Positron emission tomography
Procedures
TOP 7

Nuclear medicine
procedure

Bone

Bone imaging

Heart (201Tl)

Myocardial perfusion

Heart (

99m

Tc)

Tumour imaging PET
and PET/CT

Myocardial perfusion,
exercise and rest

Median (min-max)
contribution to total per
caput effective dose (%)

Tc phosphates/
phosphonates

38.7 (6.4–85.6)

Tl Chloride

3.8 (0.3–55.1)

Tc MIBI14.2 (1.6–50.2)

Tc Tetrofosmin

10.2 (2–37.8)

99m

201

Myocardial perfusion,
exercise and rest

99m

99m

Tumour imaging PET

18

F-FDG

8.1 (0.2–24.6)

Tumour imaging PET anddiagnostic CT

18

F-FDG

8.1 (0.4–33.9)

Tc pertechnetate

3.9 (0.1–51.5)I

2.7 (0.1–75.2)

Tc MAA

1.6 (0.2–24.9)

Thyroid (99mTc)

Thyroid imaging(no blocking)Thyroid (131I)

Thyroid metastases (after
ablation, uptake 0%)

Lung

Lung perfusion

Total median1.

Radiopharmaceutical

99m

131

99m

91.3

Myocardial perfusion imaging

D37.
Myocardial perfusion imaging (MPI) is one of the main contributors, and in some countries
the major contributor, to the nuclear medicine component of the population dose (table D5). Over the
past two decades, its use has grown rapidly worldwide to 15–20 million procedures annually anddiffusion of technology and expertise has led to its continued adoption across the world. A variety of
protocols can be used to perform MPI on SPECT and PET cameras, and a variety of approaches andbest practices have been developed to lower radiation exposure to patients. In 2013, the International
Atomic Energy Agency (IAEA) undertook a study known as IAEA Nuclear Cardiology Protocols
Cross-Sectional Study (INCAPS) to characterize worldwide nuclear cardiology practice and its impact
on radiation exposure to patients and populations, including variation in radiation doses and the use ofbest practices and dose-lowering techniques [E7].

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

271

D38.
The INCAPS [E7] collected data on 7,911 patients undergoing MPI in 308 laboratories in
65 countries, during a specified one-week period between 19 March and 22 April 2013. Mean patientage was 64.1±12 years, and 41% were female. Mean effective dose (E) for all patients was
10.0±4.5 mSv (range 2.2–24.4 mSv). The distribution of patient effective doses showed a slight
positive skew, with 978 patients (12%) receiving an estimated E of >15 mSv. Both mean and median E
differed between laboratories, countries, and world regions (P < 0.001 for each). Worldwide, only 30%
of laboratories had median E ≤9 mSv as recommended in professional society guidelines [C3].
D39.
The burden of radiation to patients undergoing MPI differed between world regions. Europe
had both the lowest mean (7.9 mSv) and median (8.0 mSv) E, and the highest proportion of patientswith E ≤9 mSv (60%). Latin America (11.8 mSv) and Asia (11.4 mSv) had the highest mean effective
doses and the second lowest proportion of patients with E ≤9 mSv (27 and 24%, respectively).
D40.
The acquired data were also used to determine each laboratory’s adherence to eight bestpractices with bearing on radiation exposure, on the basis of current clinical practice guidelines [C3].
These quality indices (QIs) included practices such as avoiding administering too much isotope,
avoiding higher dose isotopes (viz. thallium-201), and using newer technologies that can lower
radiation doses [E7]. The INCAPS found lower E in patients who underwent MPI in laboratories
adhering to more of the specified best practices, thereby providing validation of these practices. The
lowest median E (8.0 mSv) and highest proportion of laboratories with median E ≤9 mSv occurred inEurope, which had the second highest regional best practice adherence (mean laboratory QI 6.2) andwas home to more than three quarters of all laboratories observed worldwide with perfect QI scores ofeight. The highest median radiation dose (12.1 mSv) and lowest proportion of laboratories with medianE ≤9 mSv (11%) occurred in Latin America, which also had the lowest proportion of laboratories with
QI scores of at least 6. North American laboratories also performed poorly in terms of mean E and QIs.
The INCAPS data have been further analysed on a regional basis for Oceania (Australia and New
Zealand) [B18], Europe [L8], Latin America [V7] and the United States [M6].
D41.
Japan was represented by only one laboratory in the INCAPS study. However, a nationwide
survey was conducted there in 2016 with responses from 431 facilities [O7]. The mean effective dose E
was 14.0±5.5 mSv (range: 3.9 to 25.2 mSv), which was higher than that reported in most countries in
the INCAPS probably because more than 50% of the facilities still used 201Tl chloride.

2.

Patient dose from hybrid imaging

D42.
As noted above, whole-body PET imaging is now routinely performed together with a lowdose whole-body CT scan (usually head to mid-thigh) for both attenuation correction of the PET
images and for improved anatomical localization of any observed lesions. 18F-FDG PET imaging has
become the mainstay of nuclear oncology. The effective dose from the computed tomography
component is often of similar magnitude to that from the radiopharmaceutical (table D19), so that a
total procedure dose of 14 mSv is not uncommon. The introduction of time-of-flight PET scanners has
the potential to reduce this dose by allowing images of an equivalent diagnostic quality to be produced
using a lower activity of 18F. In a national survey of French PET units, Étard et al. [E9] found that the
average 18F-FDG administered activity was significantly less in the units with time-of-flight(3.4 MBq/kg) compared with those units without this technology (4.6 MBq/kg).
D43.
PET/CT systems are increasingly being used in the paediatric malignancy care and often
require multiple procedures over a period of time. Chawla et al. [C4] studied 248 PET/CT procedures
performed on 78 patients, aged 1.3 to 18 years. The average number of procedures per patient was 3.2(range 1 to 14) and the average cumulative effective dose was 64.4 mSv (range 2.7 to 326 mSv).

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UNSCEAR 2020/2021 REPORT

Table D19. Effective dose from PET/CT whole-body procedures in adults performed using 18F-FDG
CT: Computed tomography; FDG: Fluoro-2-D-deoxyglucose; PET: Positron emission tomography
CountryaYear/Period

F-FDG
(MBq)

PET dose(mSv)

Low dose
CT (mSv)

Total dose(mSv)

Reference

18

Australia

2010

304

6

8.2

14.2

[W9]

France

2011

300

5.7

8.6

14.3

[E9]

Germany

2004

370

7

2.9

9.9

[B32]

Republic of Korea

2015

370

5.9

6.3

12.2

[K18]

Russian Federation

2011–2013

220–380

4–7

6

10–13

[Z2]

2014–2017

280

5.3

13.3

18.6

[C9]

Taiwan, China

2008

370

6.8

5.9

12.7

[C6]

United Kingdom

2015

400

7.6

6.5

14.1

[I7]

a

Scans were mainly performed as diagnostic scans rather than using a low dose protocol [C9].

D44.
There are few published data on surveys of the effective dose from SPECT/CT procedures.
However, two national surveys have been conducted in Australia [A9] and in the United Kingdom [I7].
Both surveys included the median DLP from the computed tomography component of the SPECT/CT
study, which are presented in table D20 together with the effective dose calculated using the E/DLP
conversion factors published by Shrimpton et al. [S14]. In both studies, the computed tomographyacquisition parameters had been optimized for either attenuation correction only, or for attenuation
correction and lesion localization.
Table D20. Dose length product (mGy cm) and corresponding effective dose components fromcomputed tomography of clinical attenuation correction and anatomical localization examinationsin adults using SPECT/CT in Australia and United Kingdom
CT: Computed tomography; DLP: Dose length product
Country

DLP (mGy cm)
MedianCT component
Effective dose (mSv)

Australia [A10]401United Kingdom [I7]

34

0.8

Australia [A10]

170

3.4

United Kingdom [I7]

114

2.3

Australia [A10]

205

1.2

United Kingdom [I7]

122

0.7

Australia [A10]

115

3.1

United Kingdom [I7]

153

4.1

Brain

Australia [A10]

225

0.5

Pulmonary

Australia [A10]

95

2.6

Metaiodbenzylguanidine

Australia [A10]

161

3.9

United Kingdom [I7]

128

3.5

Examination

Cardiaca

Skeletal (lumbar spine)

Parathyroid

Sentinel node

Post-thyroid ablationaAttenuation correction only.

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

273

V. DISTRIBUTIONS BY AGE AND SEX
A. UNSCEAR Global Survey data
D45.
The age distributions and the percentage of males and females are presented for the two mostcommon SPECT procedures, cardiovascular (99mTc and 201Tl combined) (figure D-III) and skeletal(figure D-IV), and for the PET oncology procedures (figure D-V).
D46.
The age distributions of cardiac studies (figure D-III) are all very similar, peaking between
ages 55 and 74. The exceptions are Iceland, which peaks later, and Poland, which has a significant
paediatric contribution. The sex ratio (table D21) is quite variable, with four countries that examined
more males than females, five countries more females than males, and four countries approximately thesame number of each.
Figure D-III. Age distribution for nuclear medicine SPECT cardiovascular procedures
SPECT: Single photon emission computed tomography

D47.
Figure D-IV shows that most countries have the highest distribution of SPECT skeletal
procedures in the 65–74 age range. The exceptions are Belgium and Luxembourg, which peak in the
45–54 age range. The sex ratio (table D22) is highly variable with five countries that examined moremale patients than females and seven countries more female patients than males, and Poland examined
approximately the same number for both sexes.
D48.
Most of the countries (figure D-V) show a broad peak in the age distribution for PET oncology
procedures between approximately 55–84 years. The Brazilian data include a significant contribution
from paediatric and young adult patients. In most countries more male patients are undergoing PET
oncology procedures with Estonia being an exception examined more females than males (table D23).

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UNSCEAR 2020/2021 REPORT

Table D21. Distribution of male and female patients undergoing SPECT cardiovascular procedures
SPECT: Single photon emission computed tomography
CountryaDistribution (%)
Male

FemaleAustralia

50.4

49.6

Belgium

56.1

43.9

Brazil

44.8

55.2

Croatia

51.7

48.3

Czech Republic

54.3

45.7

Denmark

49.2

50.8

Estonia

40.6

59.4

France59.6

40.4

Iceland a

23.5

76.5

Luxembourg

57.6

42.4

Poland43.7

56.3

Thailand

31.2

68.8

United Kingdom

51.6

48.4

Data are based on only 85 patients in total (20 males and 65 females).

Figure D-IV. Age distribution for nuclear medicine skeletal procedures (gamma camera/SPECT)SPECT: Single photon emission computed tomography

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

Table D22. Distribution of male and female patients undergoing gamma camera and/or SPECT
skeletal procedures by country
SPECT: Single photon emission computed tomography
Country

Distribution (%)
Male

FemaleAustralia

44.2

55.8

Belgium

38.4

61.6

Brazil60.5

39.5

Croatia

44.9

55.1

Czech Republic

46.1

53.9

Denmark

60

40

Estonia

72.9

27.1

France41.5

58.5

Iceland56

44

Luxembourg

38.5

61.5

Poland49.5

50.5

Thailand39

61

United Kingdom

55.5

44.5

Figure D-V. Age distribution for nuclear medicine PET oncology procedures
PET: Positron emission tomography

275

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UNSCEAR 2020/2021 REPORT

Table D23. Distribution of male and female patients undergoing PET oncology procedures
PET: Positron emission tomography
Distribution (%)

Country

Male

FemaleAustralia

57.7

42.3

Belgium

59.1

40.9

Brazil51

49

Croatia

51.1

48.9

Czech Republic

50.5

49.5

Denmark

54

46

Estonia

47.1

52.9

France52.1

47.9

Luxembourg

55.9

44.1

Poland51.5

48.5

Thailand

54.9

45.1

United Kingdom

55.5

44.5

B. Literature review data
D49.
The age distribution of patients undergoing nuclear medicine procedures is rarely reported, but
has been published for the United States [M9], Luxembourg [S12] and Germany [B33] and issummarized in tables D24 and D25. In these countries, most patients are in the 40–75 year age range.
Table D24. Comparison of age distribution of nuclear medicine patients in Luxembourg [S12] andUnited States [M9]Distribution (%) per age group (year)
Country

0–10

11–17

18–24

25–34

35–44

45–54

55–64

65–74

75–84

>85

Luxembourg

1

0.7

4.6

11

15.8

18.8

18.9

19.1

8.8

1.3

United States

1.1

1.2

1.5

5.8

10.5

19.2

22

20.9

14.7

3.2

D50.
The age distribution in the United States in 2003 was virtually identical to the age distribution
found for all nuclear medicine procedures in 1980 [M9]. At that time, 37.8% of procedures were carriedout in patients aged 45 to 64 years and 39% were in patients over the age of 64. These can be comparedwith 41.2 and 38.8%, respectively, found for the same age groups in 2003.
D51.
The age distribution is not the same for all procedures as shown in table D25. In Germany[B33] myocardial studies are rarely performed in patients under the age of 45 years and only 10–15%
were older than 75 years, while the distribution is quite different for lung procedures, where up to 20%
of patients were aged less than 45 and 25% were over 75.

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

277

Table D25. Age distribution for SPECT procedures performed in Germany (2007–2008) [B33]
MAA: Macroaggregated albumin; MIBI: Methoxy isobutyl isonitrile; SPECT: Single photon emission computed
tomography
Distribution (%) per age group (year)

Examination

16–30

31–45

46–60

61–75

>75

Brain

1.7

10.2

22.1

48.6

17.4

Tumour imaging, octreotide

4.2

11.2

32

43.5

9.1

Skeleton, malignant disease, bisphosphonates

1.6

8.2

27.3

46

16.9

Skeleton, benign disease, bisphosphonates

4.2

13.7

29.3

36

16.8

Lung, ventilation

6.4

15.2

19.4

37.3

21.7

Lung, perfusion, 99mTc-MAA

4.2

9.2

20.5

42.5

23.6

Myocardium, ventriculography

2.2

10.8

34.8

42.8

9.4

Myocardium, vitality, 201Tl chloride

0.8

8.4

31

47.6

12.2

Myocardium, vitality, MIBI

0.4

5.2

26.1

52.6

15.7

Parathyroid, MIBI

3.4

14.3

29.5

39.1

13.7

D52.
Zvonova et al. [Z2] reported on the number of nuclear medicine procedures among children in
10 hospitals in the Russian Federation in 2011–2013 (table D26). The authors indicated that 12.7% of
the procedures were performed in children aged 0–2, 23.1% in the 3–7 age range, 31.8% in the 8–12
age range and 32.4% in the 13–17 age range. The majority of all nuclear medicine procedures for eachage group were renal scans. The contribution of bone, lung and heart examinations increased with age,while whole body and liver examinations remained approximately constant.
Table D26. Age distribution of nuclear medicine examinations in children in Russian Federation [Z2]
PET: Positron emissions tomography
Examined organ

Number of procedures per age group (year)
0–2

3–7

8–12

13–17

0–17

Kidney

135

244

368

376

1 123

Bone

1

19

51

61

132

Whole bodya

58

59

52

63

232

Liver

26

25

39

46

136

Brain a

44

105

116

76

341

Lung

1

16

14

24

55

Heart

1

15

12

30

58

Thyroid

1

1

12

6

20

1

4

485

668

Other
Total
a

267

PET procedures were performed in only one specialized hospital.

5
682

2 102

278

UNSCEAR 2020/2021 REPORT

D53.
O’Connor et al. [O2] reviewed computed tomography, MRI, nuclear medicine and ultrasoundstudies in paediatric patients in Ireland in the period 2003–2012 and found a 13% increase in nuclear
medicine procedures. Approximately 70% of these studies were renal examinations. Table D27 shows
the number of procedures by age groups reported in this study, with the percentage of the total.
Table D27. Age distribution of paediatric nuclear medicine procedures in Ireland [O2]
Number of procedures per age group (year)

Parameter

0–3

3–6

6–9

9–12

12–15

15–18

0–18

Number of procedures

7 655

2 938

1 797

1 309

974

548

15 221

Proportion to the total (%)

50

19

12

9

6

4

100

D54.
There are a number of schemes for determining the appropriate activity of a radiopharmaceutical to be administered to a child. These are usually based on either the age or the weight ofthe child. One scheme published by the European Association of Nuclear Medicine can be accessed
online [E1]. Zvonova et al. [Z2] reported on the activities administered to children and thecorresponding range of effective doses from nuclear medicine procedures in the Russian Federation in
2013. These results are presented in tables D28 and D29.
Table D28. Administered activities to children and adults in Russian Federation [Z2]
DTPA: Diethylenetriaminepentaacetic acid; FDG: Fluoro-2-D-deoxyglucose; IDA: Iminodiacetic acid;
MAA: Macroaggregated albumin; MAG3: Mercaptoacetyltriglycine; MIBG: Meta-iodobenzylguanidine
Examined organ
KidneyRadiopharmaceutical

Administered activity (MBq) per age group (year)
0–2

3–7

8–12

13–17

Adults99m

Tc-DTPA

10–40

20–50

20–70

50–20070–40099m

Tc-MAG3

4–40

15–50

4–70

11–12040–250123

I-hippuran

2–10

6–30

8–40

10–70

2–30

123

I-MIBG

25–80

75–120

100–130160

150–300

18

F-FDG

100

150

200

200–250

220–380

Lymphatic system

67

Ga-citrate

30–40

100–250100

100–500

Liver

99m

Tc-IDA

40

50

60

80

60–20099m

Tc-colloids

10–40

25–50

50–70

25–80

60–160Lung

99m

Tc-MAA7

20–80

30–10040–13075–190Brain

11

C-methionine

50–100100–300

300–500

500–700

500–700

18

F-FDG

65

80

120

140

140

Tc-pertechnetate60

7474–300

18–10040–370

I-NaI

5–10

5–10

5–10

5–10

5–10

Whole body

Thyroid99m
123ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

279

Table D29. Effective dose (mSv) from nuclear medicine procedures in Russian Federation [Z2]
CT: Computed tomography; PET: Positron emission tomography; SPECT: Single photon emission computed
tomography
Examined organ

Effective dose (mSv) per age group (year)
0–2

3–7

8–12

13–17

AdultsKidney

0.1–2

0.1–2

0.2–2

0.2–2

0.5–2

Heart

7–8

4–7

3–6

2–5

Liver

2–4

1–2

1–2

1–2

1–4

Lung

0.5

2–3

1–2

1–2

1–2

Bone

~2

3–9

1–2

1–2

2–3

8–14

5–6

5–6

4–5

1–2

~2

~2

~1

1–2

2–5

2–6

3–8

3–9

2–4 a

~12

~50

~12

10–40

Bone (SPECT/CT)
Thyroid (99m

Tc and123

I)

Whole body (99mTc and 123I)
Lymphatic system
Whole body PET ( F-FDG)

~10

~8

~7

5–6

2–7

Whole body PET/CT (18F-FDG)

~20

~18

~17

13–14

8–13

Brain PET ( F and C)

2–6

4–8

4–8

4–8

1–8

Brain PET/CT (18F and 11C)

3–7

5–9

5–9

5–9

2–9

18

18

a

11

Adult patients obtain the greatest doses from examinations with 111In-octreotide (with effective doses up to 13 mSv).

D55.
Bartlett et al. [B10] examined the paediatric nuclear medicine procedures performed inAustralia between 1985 and 2005. Although the number of procedures increased by a factor of four
during that period, peaking around the year 2000, the age distribution of the patients remained fairly
constant. Most services were either bone scans (45%) or renal scans (29%), with renal scans
predominating at younger ages and bone scans at older ages. For example, in the 0–3 age group, renal
and bone scans accounted for 71% and 10% of all scans performed while in the 17–19 age group, thefigures were 5 and 58%, respectively. The median effective dose per patient ranged from 1.3 mSv (4–7
years old) to 2.8 mSv (13–16 years old).

VI. STAFF AND DEVICES
D56.
Table D30 demonstrates the wide disparity in the availability of trained nuclear medicine
professionals across the world as reported in the UNSCEAR Global Survey. The number of physicians
practicing nuclear medicine in the United States is almost ten times higher than most other countries
although the rate of nuclear medicine procedures is comparable to that of many European countries(table D1) reflecting the differences in the health care delivery models in the different countries. The
data provided by Belgium did not differentiate between radiation technologists working in nuclear
medicine from those working in radiology so has not been included. The data from the United Kingdom
are unusual, with approximately two medical physicists and seven radiation technologists per nuclear
medicine physician.

280

UNSCEAR 2020/2021 REPORT

D57.
Table D31 presents the staff of nuclear medicine departments in Latin American countries[P1]. The data were obtained from the IAEA Nuclear Medicine Database (NUMDAB), and also fromthe several ongoing IAEA regional projects. Similarly, table D32 shows information on nuclear
medicine staffing in countries of the Middle East [P2]. These data were also obtained from the IAEA
NUMDAB database.
D58.
Tables D33, D34 and D35 show the nuclear medicine equipment reported to the current
UNSCEAR Global Survey, the IAEA NUMDAB data from Latin America and the Middle East,
respectively. In a number of countries SPECT/CT systems are slowly replacing SPECT systems. For
example, table D33 shows that in Switzerland all 52 SPECT systems are now hybrid systems, while
two thirds of the SPECT systems in Australia incorporate a computed tomography scanner. The
availability of PET systems is highly variable with some countries having more than 5 per million
population (e.g., Denmark 7.4, United States 5.2), while Brazil is the only country in Latin American,
and Kuwait, Lebanon and Turkey the only Middle Eastern countries, to have more than one PET
system per million population.

Table D30. Number of nuclear medicine staff by country in absolute number and per million population as reported to UNSCEAR Global SurveyCountry

Nuclear medicine
physicians

Nuclear medicine
medical physicists a

Nuclear medicine
technologists a

Per million
population

Number

Per million
population

Number

Per million
population

Argentina

374

9.3

13

0.3

208

5.2

Australia

247

10.4

20

0.8

1 015

42.8

Bangladesh

126

0.8

Belarus

43

4.5

50

5.3

Belgium

308

27.5

35

3.1

Brazil

792

3.9

196

1

518

Brunei Darussalam

1

2.4

1

2.4

Bulgaria

57

7.7

13

Canada

280

7.6

China

3 904

Croatia

Nurses in nuclear medicine a

Number

Per million
population

Number

Per million
population

25

11

50

2.1

50

5.3

4.3

2.5

393

1.9

2 350

11.5

3

7.2

5

12

2

4.8

1.8

34

4.6

18

2.4

30

4.1

26

0.7

668

18.2

3.2

87

0.1

2 777

2.3

174

0.1

1 736

1.4

74

18

9

2.2

41

10

41

10

65

15.8

Cyprus

7

7.4

4

4.2

7

7.4

Czech Republic

199

18.8

34

3.2

75

7.1

57

5.4

314

29.7

Denmark

110

19.3

25

4.4

27

4.7

Estonia

11

8.4

5

3.8

18

13.7

2

1.5

3

2.3

Finland

104

19

France

648

9.9

74

1.1

1 470

22.4

126

1.9

Germany

1 000

12.3

Greece

296

27

277

25.3

114

10.4

86

7.8

133

12.1

Iceland3

8.7

Indonesia

45

0.2

13

0.1

13

0.1

4

0.02

26

0.1

Japan

1 393

11

281

48

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

NumberRadiopharmacists/
radiochemists aNumber

Per million
population

Number

Per million
population

Lebanon15

3.1

Lithuania

22

7.6

7

Luxembourg

12

21.1

Malaysia

37

Montenegro

Per million
population

25

5.2

2.4

20

1

1.8

1.1

75

4

6.7

Netherlands

190

11.3

Niger

4

North Macedonia

Radiopharmacists/
radiochemists a
Number

Per million
population

6.9

15

5.2

30

52.7

2

3.5

2.3

226

6.9

184

5.6

1

1.7

6

10

0.2

1

0.1

2

0.1

1

0.1

27

13

6

2.9

17

8.2

8

3.9

4

1.9

Philippines

159

1.6

17

0.2

122

1.2

4

0.04

Poland

296

7.7

63

1.6

Romania

71

3.6

26

1.3

Russian Federation

400

2.7

40

0.3

650

4.4

150

1

Spain

630

13.5

77

1.6

Sudan

12

0.3

20

0.6

25

0.7

Sweden

220

22

80

8

Switzerland

150

17.8

40

4.8

500

59.4

33

3.9

Thailand

66

1

25

0.4

93

1.4

29

0.4

60

0.9

Ukraine

95

2.2

6

0.1

470

11.1

United Arab Emirates

21

60

Per million
population

Nurses in nuclear medicine a
Numbera

NumberNuclear medicine
technologists a

1.8

2.3

13

1.4

39

4.2

4

0.4

17

1.8

United Kingdom

160

b

2.4

300

4.6

1 150

17.5

30

0.5

75

1.1

United States

27 522 c

85.2

9 217

28.5

16 30750.5

11 34435.1

14 88946.1

Empty cell indicates no data available.

b

Malaysia reported an additional 50 other physicians conducting nuclear medicine procedures.

c

Nuclear medicine physicians in the United Kingdom includes 85 radiologists.

d

The numbers reported for the United States reflect the number of clinicians and other professionals whose work involves nuclear medicine. They are not all nuclear medicine physicians, nurses, etc.

UNSCEAR 2020/2021 REPORTa

Nuclear medicine
medical physicists a

282

Country

Nuclear medicine
physiciansTable D31. Staff of nuclear medicine departments in Latin American countries [P1], excluding those reported to UNSCEAR Global Survey
Nuclear medicine
physicians

Nuclear medicine
medical physicists a

Nuclear medicine
technologists a

Radiopharmacists/
radiochemists a

Number

Per million
population

Number

Per million
population

Number

Per million
population

Number

Per million
population

Bolivia

9.9

13

1.3

1

0.1

10

1.0

11

1.1

Chile

17

44

2.6

2

0.1

61

3.6

9

0.5

Colombia

45.7

82

1.8

12

0.3

86

1.9

24

0.5

Costa Rica

4.6

5

1.2

1.2

0.3

20

4.3

8

1.8

Cuba

11.2

35

3.1

24

2.1

65

5.8

13

1.1

Dominican Republic

10

13

1.3

1

0.1

16

1.6

Ecuador

13.6

10

0.7

14

1.0

El Salvador

6.1

2

0.3

5

0.8

Guatemala

14

4

0.3

12

0.9

Haiti

10

0

0.0

0

Honduras

7.5

1

0.1

2

Jamaica

2.7

1

0.4

0

Mexico

116

242

2.1

Nicaragua

5.7

2

0.4

1

0.2

Panama

3.4

5

1.5

Paraguay

6.3

3

0.5

Peru

29.1

47

1.6

Uruguay

3.4

32

9.7

Venezuela

28.6

23

0.8

31

Total

571.8

1 265

2.2

129

a

Empty cell indicates no data available.

6

1

5

0.1

0.3

128

1.1

2

0.4

8

2.4

6

1

59

2

4

0.1

44

13

16

4.8

1.1

40

1.4

3

0.1

0.2

2 205

3.9

146

0.3

0.3

0.2

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

Population(in millions)

Country283

284

Country or region

Population(in millions)

Nuclear medicine
physicians a

Nuclear medicine medical
physicists a

Nuclear medicine
technologists a

Radiopharmacists/
radiochemists a

Number

Per million
population

Number

Per million
population

Number

Per million
population

Number

Per million
population

Bahrain

1.3

5

3.7

2

1.5

5

3.7

2

1.5

Egypt

83.4

105

1.3

32

0.4

95

1.1

12

0.1

Iran (Islamic Republic of)

78.5

200

2.5

123

1.6

400

5.1

23

0.3

Iraq

34.3

11

0.3

21

0.6

10

0.3

5

0.1

Israel

8.2

75

9.1

7

0.9

85

10.3

5

0.6

Jordan

6.6

29

4.4

20

3

34

5.1

5

0.8

Kuwait

3.5

50

14.4

10

2.9

150

43.1

10

2.9

Oman

3.9

9

2.3

14

3.6

17

4.3

0

0

Palestine, State of

4.4

1

0.2

0

0

1

0.2

0

0

Qatar

2.3

5

2.2

3

1.3

13

5.7

3

1.3

Saudi Arabia

29.4

79

2.7

60

2

172

5.9

25

0.9

Syria

23.3

10

0.4

25

1.1

10

0.4

5

0.2

Turkey

75.8

535

7.1

250

3.3

850

11.2

70

0.9

Yemen

25

6

0.2

3

0.1

6

0.2

2

0.1

Total

390.6

1 157

3

586

1.5

1 953

5

173

0.4

a

Zero values are indicated when available; otherwise, cells have been kept empty.

UNSCEAR 2020/2021 REPORT

Table D32. Staff of nuclear medicine departments in Middle East countries [P2], excluding those reported to UNSCEAR Global Survey

Table D33. Equipment used in nuclear medicine reported to UNSCEAR Global Survey
CT: Computed tomography; PET: Positron emission tomography; SPECT: Single photon emission computed tomography
Total SPECT a,b
Country

SPECT/CT a,b

Total PET a,b

PET/CT a,b

Single channel
spectrometer a,b

Gamma cameras (Planar) a,b

Per million
population

Number

Per million
population

Number

Per million
population

Number

Per million
population

Number

Per million
population

Number

Per million
population

Argentina

287

7.2

8

0.2

28

0.7

10

0.2

40

1

274

6.8

Australia

400

16.8

260

11

44

1.9

40

1.7

40

1.7

12

0.5

Bangladesh

13

0.1

4

0.03

72

0.5

35

0.2

Belarus

18

1.9

1

0.1

7

0.7

Belgium

205

18.3

129

11.5

26

2.3

24

2.1

130

11.6

Brazil

784

3.8

10

0.05

130

0.6

130

0.6

138

0.7

Brunei Darussalam

1

2.4

1

2.4

1

2.4

1

2.4

2

4.8

Bulgaria

15

2

5

0.67

7

1

7

1

1

0.1

Canada

330

9

261

7.1

51

1.4

51

1.4

China

555

0.5

215

0.2

198

0.2

Croatia

7

1.7

7

1.7

5

1.2

5

Cyprus

10

10.5

1

1.1

Czech Republic

131

12.4

46

4.3

35

3.3

45

4.3

Denmark

55

9.6

41

7.2

42

7.4

Estonia

3

2.3

3

2.3

3

2.3

3

2.3

4

3

Finland

35

6.4

35

6.4

29

5.3

13

2.4

France

474

7.1

298

4.4

162 c

2.4

158

2.4

150

1.8

5

0.5

5

0.5

Germany

2

0.3

17

0.01

1.2

12

2.9

15

1.4

30

2.8

39

6.8

42

7.4

147

13.4

7

0.6

5

0.5

Iceland

4

11.6

1

2.9

Japan

1 432

11.3

346

2.7

536 d

4.2

489

3.9

Lebanon

17

3.5

2

0.4

28

5.8

14

2.9

1

0.2

Lithuania

1

0.3

1

0.3

2

0.7

2

0.7

8

2.8

Luxembourg

7

12.3

1

1.8

2

3.5

1

1.8

2

3.5

285

GreeceANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

NumberTotal PET a,b

Per million
population

Number

Per million
population

Number

Per million
population

Number

Per million
population

Number

Per million
population

Malaysia

10

0.3

10

0.3

21

0.6

21

0.6

4

0.1

Montenegro

1

1.7

1

1.7

1

1.7

160

9.5

58

3.4

Single channel
spectrometer a,b

Gamma cameras (Planar) a,b

NumberNetherlandsa

PET/CT a,b

Number

Per million
population

1

0.1

Niger

2

0.1

North Macedonia

6

2.9

2

1

6

2.9

3

1.4

2

1

Philippines

4

0.04

4

0.04

6

0.06

6

0.06

55

0.5

Poland

76

2

42

1.1

26

0.7

26

0.7

18

0.5

Romania

14

0.7

7

0.4

12

0.6

12

0.6

32

1.6

2

0.1

Russian Federation

168

1.1

80

0.5

19

0.1

19

0.1

60

0.4

94

0.6

Spain

78

1.7

78

1.7

92

2

75

1.6

Sudan

5

0.1

2

0.06

Sweden

61

6.1

50

5

20

2

17

1.7

5

0.5

25

2.5

Switzerland

52

6.2

52

6.2

41

4.9

39

4.6

15

1.8

10

1.2

Thailand

26

0.4

19

0.3

14

0.2

14

0.2

23

0.3

Turkey

359

4.5

39

0.5

136

1.7

133

1.7

Ukraine

19

0.4

4

0.1

3

0.1

3

0.1

21

0.5

29

0.7

United Arab Emirates

21

2.3

6

0.6

4

United Kingdom

460

7

240

United States

12 931

40

1 967

0.4

4

0.4

1

0.1

3.7

77

e

1.2

70

1.1

40

0.6

6.1

1 680

5.2

1 596

4.9

1 124

3.5

Empty cell indicates no data available.

b

Values are rounded; however extended precision has been preserved to illustrate differences.

c

Includes 4 PET/MRI systems.

dIncludes 9 PET/MRI systems.

eIncludes 7 PET/MRI systems.

UNSCEAR 2020/2021 REPORTCountry

SPECT/CT a,b

286

Total SPECT a,b

Table D34. Equipment used in nuclear medicine centres in Latin American countries [P1], excluding those in UNSCEAR Global Survey
CT: Computed tomography; PET: Positron emission tomography; SPECT: Single photon emission computed tomography
SPECT/CT a,b

SPECT a,bCountry

Population(in millions) a

Total gamma
cameras a,b

Gamma cameras(Planar) a,b

PET a,b

Number

Per million
population

Number

Per million
population

Number

Per million
population

Number

Per million
population

Number

Per million
population

9.9

8

0.8

0

0.0

3

0.3

11

1.1

0

0.0

Chile

17

45

2.6

6

0.4

4

0.2

55

3.2

10

0.6

Colombia

45.7

78

1.7

4

0.1

0

0.0

82

1.8

9

0.2

Costa Rica

4.6

7

1.5

0

0.0

2

0.4

9

2

1

0.2

Cuba

11.2

13

1.2

1

0.1

1

0.1

15

1.3

1

0.1

Dominican Republic

10

12

1.2

0

0.0

1

0.1

13

1.3

1

0.1

Ecuador

13.6

3

0.2

3

0.2

1

0.1

7

0.5

2

0.1

El Salvador

6.1

2

0.3

0

0.0

0

0.0

2

0.3

0

0.0

Guatemala

14

3

0.2

0

0.0

4

0.3

7

0.5

0

0.0

Haiti

10

0

0.0

0

0.0

0

0.0

0

0.0

0

0.0

Honduras

7.5

2

0.3

0

0.0

0

0.0

2

0.3

0

0.0

Jamaica

2.7

1

0.4

0

0.0

1

0.4

2

0.7

0

0.0

Mexico

116

260

2.2

25

0.2

0

0.0

285

2.5

35

0.3

Nicaragua

5.7

1

0.2

0

0.0

0

0.0

1

0.2

0

0.0

Panama

3.4

3

0.9

4

1.2

0

0.0

7

2.1

1

0.3

Paraguay

6.3

5

0.8

0

0.0

0

0.0

5

0.8

1

0.2

Peru

29.1

35

1.2

2

0.1

2

0.1

39

1.3

3

0.1

Uruguay

3.4

14

4.2

3

0.9

0

0.0

17

5.1

2

0.6

Venezuela

28.6

28

1

1

0.0

13

0.5

42

1.5

6

0.2

Total

571.8

1 064

1.9

87

0.2

80

0.1

1 231

2.2

161

0.3

a

c

Values are rounded; however extended precision has been preserved to illustrate differences.
Zero values are indicated when reported.

c

Total values as reported in [P2], including countries that reported data to the UNSCEAR Global Survey.

287b

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Bolivia288

Table D35. Equipment used in nuclear medicine centres in Middle East countries [P2], excluding those reported to UNSCEAR Global SurveyCountry

Population(millions) a

Gamma cameras and SPECT a,b

SPECT/CT a,b

Gamma cameras a,b

PET a,b

Number

Per million
population

Number

Per million
population

Number

Per million
population

Number

Per million
population

Bahrain

1.3

3

2.2

1

0.7

4

0.7

1

0.7

Egypt

83.4

65

0.8

9

0.1

74

0.1

15

0.2

Iran (Islamic Republic of)

78.5

200

2.5

8

0.1

208

0.1

3

0.04

Iraq

34.3

5

0.1

0

0.0

5

0.0

0

0

Israel

8.2

63

7.7

26

3.2

89

3.2

9

1.1

Jordan

6.6

13

2

0

0.0

13

0.0

6

0.9

Kuwait

3.5

30

8.6

6

1.7

36

1.7

6

1.7

Oman

3.9

3

0.8

2

0.5

5

0.5

2

0.5

Palestine, State of

4.4

1

0.2

0

0.0

1

0.0

0

0

Qatar

2.3

3

1.3

1

0.4

4

0.4

1

0.4

Saudi Arabia

29.4

49

1.7

34

1.2

83

1.2

13

0.4

Syria

23.3

2

0.1

2

0.1

4

0.1

2

0.1

Yemen

25

5

0.2

0

0.0

5

0.0

0

0

Total

390.6

803

2.1

107

0.3

910

0.3

194

0.5

a

c

Values are rounded; however extended precision has been preserved to illustrate differences.

b

Zero values are indicated when reported.

c

Total values as reported in [P2], including countries that reported data to the UNSCEAR Global Survey.

UNSCEAR 2020/2021 REPORT

CT: Computed tomography; PET: Positron emission tomography; SPECT: Single photon emission computed tomography

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

289

VII. TRENDS
A. Frequency of nuclear medicine procedures
D59.
Eleven articles presented data on trends in exposure from nuclear medicine. The biggest
change in the past decade has been the steady increase in the number of PET procedures. For example,
in Finland PET procedures increased by 70% between 2006 and 2009 even though there was a slightdecrease in the overall number of nuclear medicine procedures [B19]. In Japan, while single-photon
studies decreased by 19% between 2007 and 2012, PET studies increased by 25% during the same
period [K10]. Similarly, a 3% annual decline in nuclear medicine procedures between 1996 and 2010
was reported in the United States while PET studies simultaneously increased by 57% annually [S18].
In the United States, there have also been significant changes in the type of nuclear medicine
procedures performed. Between 1980 and 2006, cardiac procedures increased by 450% while lungprocedures decreased by 38% compared to 1982 [M10].
D60.
In other countries the number of nuclear medicine procedures continued to increase. In France
they increased by 40% between 2002 and 2007 [E10], in Taiwan, China they increased by 42%
between 1997 and 2008 [C6], while in the Republic of Korea they increased by 90% between 2006 and2013 with PET/CT increasing by 30% [L3] (table D36).
Table D36. Trends of nuclear medicine procedure frequencies and related collective effective doses
in Republic of Korea for the period (2006-2013) [L3]
Parameter

Year
2006

2007

2008

2009

2010

2011

2012

2013

Frequency per 1 000
population

336

431

489

532

578

603

618

640

Collective effective dose(man Sv)

3 590

4 838

5 662

6 212

6 791

7 065

7 299

7 606

Annual per caput effective
dose (mSv)

0.07

0.10

0.11

0.12

0.13

0.14

0.14

0.15

D61.
Mettler et al. [M9] reported on the change in nuclear medicine procedures in the United States
between 1973, 1982 and 2005, in terms of both the absolute number of procedures and the percentageof the total of procedures (table D37). Although PET scans were available in the United States in 2005
these were not included in the number of examinations reported, although Mettler et al. estimated thenumber to be approximately 5% of all nuclear medicine procedures. The most significant change noted
was the rapid rise in the number of cardiac procedures which increased by a factor of 10 between 1982
and 2005 so that they accounted for 57% of all procedures in 2005. During the same period, the use of201
Tl chloride for many of the myocardial perfusion studies was replaced by 99mTc radiopharmaceuticals(sestamibi or tetrofosmin), which resulted in substantially lower patient doses per procedure. The
current UNSCEAR Global Survey indicates that this trend has reversed in the past decade with cardiac
procedures declining. There have been similar trends for some other procedures, notably bone scans.
PET tumour imaging has increased, now accounting for 14.6% of all nuclear medicine procedures.

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Table D37. Comparison of diagnostic nuclear medicine procedures in the United States since 1973
[M9] and reported to UNSCEAR Global Survey
PET: Positron emission tomography. Empty cell indicates no data available
Procedure

1973

1982

2005

Current evaluation

Number(1 000)

Proportion(%)

Number(1 000)

Proportion(%)

Number(1 000)

Proportion(%)

Number(1 000)

Proportion
(%)

Bone

125

3.6

1 811

24.5

3 450

20

1 670

12.3

Cardiac

33

1

950

12.8

9 800

57

6 440

47.6

Lung

417

11.9

1 191

16.1

740

4

690

5.1

Thyroid

460

13.1

677

9.1

339

2

590

4.4

Renal

122

3.5

236

3.2

470

3

360

2.7

Gastro

535

15.2

1 603

21.7

1 210

7

930

6.9

Brain

1 510

43

812

11

<2

200

1.5

380

2

280

2.1

340

2

400

3

1 970

14.6

13 530100

Infection
Tumour

14

0.4

121

1.6

PET
Other

294

8.4

Total

3 510

100

<2
7 400

100

17 200100

D62.
The EC DDM 1 project [E3] included studies conducted within the period 1998–2005, and EC
DDM 2 project [E5], included studies for the period 2007–2011. The EC DDM 1 project included eight
European countries, one of which, Belgium, did not provide data for the EC DDM 2, leaving sevencountries for which a comparison of the frequency of nuclear medicine procedures is presented intable D38. Overall, the frequency of these procedures decreased between the two surveys although thechanges were not consistent across the seven countries.
Table D38. Comparison of averaged frequency per 1,000 population between EC DDM 1 [E3] and EC
DDM 2 [E5] projects for specific nuclear medicine proceduresCountryHeart

Bone scan(99mTc)Thyroid

Lung perfusion(99mTc)

Renal

DDM 1

DDM 2

DDM 1

DDM 2

DDM 1

DDM 2

DDM 1

DDM 2

DDM 1

DDM 2

Germany

11

10

5

5

17

15

3

0.7

3

1

Luxembourg

13

14

6

4

11

10

2

1

1

0.5

Netherlands

6

6

4

3

1

0.5

3

0.4

1

0.8

Norway

4

3

3

2

1

0.7

1

0.2

1

0.9

Sweden

3

2

2

3

1

0.7

1

0.6

2

0.6

Switzerland

5

4

3

2

1

0.6

1

0.3

1

0.2

UnitedKingdom

3

3

2

2

0.3

0.3

3

2

2

1

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

291

D63.
The Japan Radioisotope Association has performed a nationwide survey of in vivo and in vitro
nuclear medicine practice every five years since 1982. The most recently reported survey was in 2017
[J9]. In 2017, there were 1,249 institutes performing nuclear medicine procedures, with 1,156
performing single photon imaging and radionuclide therapy. There were 389 institutes with PET
imaging facilities, which represented an increase of 32% over 5 years. Although the number of gamma
cameras in Japan fell from 1,425 in 2012 to 1,332 in 2017, this now included 314 SPECT/CT systems,
more than double the number in 2012 (149). Table D39 presents the annual estimates of nuclear
medicine procedures in Japan from 1992 to 2017. During that 25-year period, the number of singlephoton procedures has decreased by 34% while the number of PET procedures has increased by a factorof 120. The number of therapy procedures remained relatively constant from 1992 to 2007, but has
increased by 117% in the past decade due to a continued increase in the treatment of thyroid disorders(both hyperthyroidism and thyroid cancer) and the introduction of 89Sr therapy for bone pain palliation
and 90Y-ibritumomab tiuxetan (Zevalin) for lymphoma.
Table D39. Annual number of nuclear medicine procedures in Japan [J9]
PET: Positron emission tomography
Modality category

Year
1992

1997

2002

2007

2012

2017

1 650 000

1 860 000

1 621 200

1 417 700

1 149 900

1 083 800

PET procedures

5 900

11 20026 100414 300

575 800

711 800

Radionuclide therapies

4 000

3 100

5 000

6 500

10 50014 100Diagnostic nuclear
medicine procedures

D64.
The trends reported in the literature are supported by the changes observed between the
UNSCEAR 2008 Report [U9] and the current survey. As shown previously in table D1, the frequencyof nuclear medicine procedures per 1,000 population has fallen significantly in a number of European
countries, while increasing significantly in others. The average change in frequency of nuclear
medicine procedures since the UNSCEAR 2008 Report [U9] was +14%, with a population-weighted
average change of +3% (excluding the very high percentage change recorded in Belarus).
D65.
Table D40 examines the changes between the UNSCEAR 2008 Report [U9] and UNSCEAR
Global Survey for those countries which reported radionuclide therapy data in both surveys. Six
countries showed reductions in the frequency of radionuclide therapy, while others showed substantial
increases. Overall, for the 14 countries there was an average increase of 33%, with a populationweighted increase of 10%, since the UNSCEAR 2008 Report [U9].

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UNSCEAR 2020/2021 REPORT

Table D40. Comparison of averaged radionuclide therapy frequencies per 100,000 population
between UNSCEAR 2008 Report [U9] and UNSCEAR Global SurveyCountry

UNSCEAR 2008 Report [U9]Current evaluation

Variation (%)

Czech Republic

27.2

18.5

–32

Estonia

41.4

65.5

58

Finland

44

34.2

–22

Greece

12

27.5

129

Hungary

32.9

15.3

–54

Iceland

34.7

32.3

–7

Japan

3.5

8.3

139

Luxembourg

10.8

32.7

202

Netherlands

38.4

14.5

–62

Norway

20.9

26.6

27

Poland

33.6

54.4

62

Sweden

34.5

45.3

31

Switzerland

30.9

38.1

23

United Kingdom

24.4

13.3

–46

B. Trends in nuclear medicine imaging systems
D66.
Throughout the world, PET/CT systems have now largely replaced stand-alone PET
systems. Commercial SPECT/CT systems have been available since about 2005, however
information on their distribution is very limited. A nationwide survey was conducted in the United
Kingdom in 2014 and found 193 SPECT/CT systems at 135 sites compared to 57 sites with PET/CT[I7]. In Belgium, the Federal Public Service provides regularly updated online maps of the
distribution of PET/CT and SPECT/CT systems [S21]. In the Republic of Korea, PET/CT procedures
ranked the highest average annual increasing rate of 49.4% and have rapidly increased by 800%
between 2006 and 2013 in tandem with an increase in the number of PET-CT scanners of over 200%
during the same period [L3].
D67.
The European Coordination Committee of the Radiological, Electromedical and Healthcare IT
Industry published age and density (number of systems in use per million population) data of computed
tomography, angiography equipment, MRI and molecular PET equipment. The density profile for PET
equipment installed in Europe from 2015 is shown in figure D-VI [C11].

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

293

Figure D-VI. Density of installed PET systems per million population in Europe in 2015 [C11]
PET: Positron emission tomography

D68.
Table D33 presents a detailed analysis on the use of hybrid systems across the world as foundin the UNSCEAR Global Survey. Thirty-three countries provided data on PET and PET/CT systems.
Of these, 16 used PET/CT systems exclusively while in a further eight countries PET/CT accounted formore than 90% of installations. Although data on PET/MRI systems were not requested in the current
survey, Japan reported that nine of the 536 PET systems were combined PET/MRI units. Forty
countries reported on SPECT and SPECT/CT systems. Globally, SPECT/CT accounted for 22% of all
SPECT installations and this number is likely to rise as older SPECT systems are replaced.
D69.
It is important to note that in many cases performed on a SPECT/CT system, the computed
tomography component is not used. This is highlighted in table D11 which presents the percentage ofstudies that included a computed tomography scan. Finland, which has only SPECT/CT systems, usedthe computed tomography in a maximum of 40% of cases. Usually, the SPECT study is performed first,
and computed tomography is performed only if the SPECT scan was abnormal, and the anatomical
localization of the abnormality is in doubt.

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VIII. SUMMARY
D70.
The UNSCEAR Global Survey included a detailed questionnaire on nuclear medicine practiceacross the world and the submitted data were analysed to estimate the frequency of nuclear medicine
procedures, the administered activity of each radiopharmaceutical, and the resulting effective dose foreach country. For hybrid systems, the frequency of computed tomography examinations together withthe corresponding dose-length product and effective dose were calculated.
D71.
The effective dose from the administered radiopharmaceutical has been calculated from dosecoefficients (mSv/MBq) from ICRP publication 128 [I15], which uses a mathematical human phantom
and ICRP 60 tissue weighting factors [I9]. A revised publication by the ICRP is expected to beavailable soon, which will use anthropomorphic models derived from whole body computed
tomography and tissue weighting factors from ICRP 103 [I11].
D72.
The frequency of radionuclide therapy was found to have increased by 33% since the
UNSCEAR 2008 Report [U9]. In the past decade, a number of new therapies have been introduced
clinically and are now available in many countries. These include 90Y-microspheres for the treatment ofliver tumours, 177Lu-octreotide for neuroendocrine tumours and 177Lu-PSMA for prostate cancer.
Statistics on the use of these newer therapies are often limited, so the frequencies estimated in thecurrent evaluation are likely to be an underestimate. There is considerable research activity underway
into “theranostics”, in which the same chemical vector is used for both diagnosis and treatment, using
different radionuclides. This is likely to lead to the establishment of these new procedures in routine
clinical practice in many countries.
D73.
The uncertainty in each of these estimations arises from several sources. Firstly, a number ofcountries conducted a survey of a limited number of nuclear medicine practices and then extrapolated
the data to the whole country. This can lead to an over- or underestimate, depending on how
representative of the whole country the sample sites were. Secondly, often a number of different
radiopharmaceuticals are available for any one procedure and the particular one used may vary fromsite to site and also from patient to patient, depending on their clinical history. Thirdly, while computed
tomography is now used in almost all PET procedures, this is not the case with SPECT. Although thenumber of SPECT/CT installations has increased markedly in the past decade, the survey showed(table D11) that the computed tomography component is usually used in less than 55% of cases. It is acommon practice to perform the SPECT study first, and then perform the computed tomography only if
the study is abnormal and the anatomical localization of the abnormality cannot be clearly identified
from the SPECT images. This level of detail is often not available in national surveys but needs to beconsidered for future surveys.
D74.
Despite the limitations of the UNSCEAR Global Survey, the results indicate that the frequencyof nuclear medicine procedures, while declining in a number of European countries and United States,
has increased globally by about 16% since the UNSCEAR 2008 Report [U9]. The frequency of
diagnostic nuclear medicine procedures was found to average 12.4 per 1,000 population contributing toabout 7% to the global collective effective dose. PET procedures continue to increase in number and
now represent 17% of all nuclear medicine procedures. The use of PET is likely to increase further with
their growing role in cancer care and the initiation of new radiopharmaceuticals that are currently underclinical development.

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295

APPENDIX E. TRENDS IN USE OF RADIATION THERAPY

I. INTRODUCTION
E1.
Radiation therapy for cancer treatment, unlike most other cancer treatment modalities, is a
precise and extremely quantitative modality. In contrast to surgery, where the target tissue must often
be exposed so as to be visible to the surgeon, radiation therapy is largely non-invasive and requires
means other than the physician’s vision to guide the radiation beam. The identification of the target
tissue is critical because, as was stated by the Harold Johns, “if you can’t see it, you can’t hit it, and if
you can’t hit it, you can’t cure it” [N5]. Early radiation therapy treatments, therefore, relied on thephysician’s best estimate of tumour location, and skin markings made through the use of X-ray imaging
systems [H8, T6].
E2.
Today, radiation therapy is delivered through external beams of radiation (teletherapy) or byplacing radioactive sources into or near the tumour tissue (brachytherapy). External radiation beams
may consist of high-energy X- or gamma rays, electrons, protons, neutrons, or heavier charged
particles. Gamma-ray beams are most often produced by high-activity sources of 60Co, while all otherexternal radiation beams are produced by linear accelerators.
E3.
Early radiation therapy treatment guidance consisted of X-ray imaging prior to treatment using
conventional X-ray imaging equipment. A major step forward came with the introduction of electronic
portal imaging equipment. Early devices generally consisted of two-dimensional arrays ofsemiconductor detectors that captured a portal image electronically, replacing radiographic film and theneed for a film developer. These devices became available in the 1990s, but the technology improved
substantially in the early 2000s, yielding to images of higher quality than the portal films they replaced.
Manufacturers began producing linear accelerators equipped with this technology as a standard. Two
key features were (a) the availability of images almost instantly after exposure, and (b) the ability tocompare images digitally with digitally reconstructed radiographs produced by treatment-planningsystems based on images acquired at computed tomography simulators. This milestone allowed true
adaptive therapy, meaning that the treatment could potentially be modified to account for variations in
the patient’s position on a daily basis. Today, this technique is used to adjust the patient’s position
following a comparison of 3D-images with 2D-images from the planning system [M13, M14].
E4.
Around the year 2000, linear accelerators manufacturers began to mount on-board kilovoltage(kV) imagers on the gantries of the systems, or elsewhere in the treatment rooms, so that almost
diagnostic-quality orthogonal patient radiographs could be obtained in the treatment position byrotating the gantry. These imaging systems facilitated the comparison of projection radiographs fromthe on-board imaging system, leading to vastly-improved 2D/3D matching [M1]. The 3D-images arecompared with reconstructed 2D-images from the planning computed tomography, and displacementsthat can be detected by software.
E5.
With the introduction of kV on-board imaging systems, there was a revival of a proposal fromyears earlier to create computed tomography images by acquiring transmission data from a portal
imaging system, but instead using the kV on-board imaging system. Rather than obtaining a single sliceof information, the device could use the entire area of the flat-panel image receptor [J1, J2]. Computed

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UNSCEAR 2020/2021 REPORT

tomography volumetric image data sets obtained from the projection beam of a kV source are known ascone beam computed tomography (CBCT) and their use has enhanced image-guided radiation therapy(IGRT) considerably [M13, T5, W6].
E6.
The use of kV (or MV) imaging for treatment guidance carries a potential for deleterious
effects resulting from additional radiation exposure. Cheng et al. [C7] have estimated the dose fromimaging, which can vary from a few milligray to as much as 16 centigray. While it is recognized that, ingeneral, the dose from imaging is far smaller than the dose from the radiation therapy itself, the volume
irradiated by imaging systems is generally far larger and likely to include sensitive normal tissues suchas the lens of the eye or breast tissue. Even though the dose from individual kV planar images or CBCT
scans is relatively low, the use of daily image guidance can result in the dose over a course of treatment
being significant in terms of biological effects [H1]. Consequently, the benefits of X-ray-based IGRT
should be weighed against possible detriment to the patient.
E7.
Techniques for cranial fixation and for delivering radiation through smaller field sizes thanthose previously used led to the introduction in the late 1980s of brain stereotactic radiosurgery, or theuse of radiation as a surgical tool to obliterate small (~1 cm or smaller) intracranial targets [L11]. In thelate 1990s and early 2000s, the aforementioned increase in the use of imaging, and also improvements
in delivery systems and developments by individual researchers, contributed to the ability to target
tumours using stereotactic radiosurgery even more precisely. Later, stereotactic radiosurgery techniques
were extended to extracranial targets in what today is called stereotactic body radiation therapy orstereotactic ablative body radiation therapy [B13]. These techniques required modification of patient
fixation techniques to allow repeat and reproducible fixation for multiple fractions, typically 3–5, to bedelivered to targets in the spine, thorax or pelvis.
E8.
Until the late 1990s, radiation dose was delivered through external beams of uniform intensity.
Exceptions to this included the use of wedged fields, and when missing-tissue compensating filters anddose-compensating filters were employed. In both cases, the intent was to compensate for overlapping
treatment fields, irregularities in the patient surface, or non-uniformities in tissue density. In 1988,
Brahme published a description of an optimization technique that delivered extremely conformal dose
distributions through the use of non-uniform radiation beams [B29]. Once computer-controlled
technology became available, and treatment machines were delivered equipped with multi-leaf
collimators, Brahme’s optimization technique was capitalized upon by Webb [W4], who quickly
developed intensity-modulated radiation therapy (IMRT) into a successful and valuable clinical tool.
Within a few years, IMRT had been adopted by a large number of clinics and today it and several
variants are used extensively by most advanced radiation therapy centres. One of the variants of IMRT
is volumetric modulated arc therapy (VMAT), in which the radiation beam intensity is modulated while
the treatment unit gantry is rotated around the patient [O8]. VMAT requires customized optimization
software and can often speed the delivery process substantially.
E9.
Particle-beam therapy allows highly precise radiation delivery, as the range of the beam can becontrolled, and little dose is scattered out of the beam. Particle-beam therapy might permit delivery ofhigher doses to tumours situated close to critical organs. From its introduction until the early 2000s,
particle-beam therapy (with protons or heavier charged particles) was most often administered using
passive scattering techniques, in which the particle beam is spread laterally by inserting material in the
beam upstream from the patient. Beams of different energies are delivered so that the individual Bragg
peaks are positioned at depths distributed through the target volume, which creates a “spread-out Bragg
Peak”. Beginning in the early 2000s, “spot scanning” techniques were introduced to spread the beam
laterally; the dose is delivered by individual pencil beams. The beams are steered electromagnetically todeliver dose in an array that spans the cross-section of the tumour as projected perpendicular to thebeam axis. To control the dose distribution in the depth direction, the energy of each “spot” is adjusted

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so that the spots are distributed. A key advantage is that the operator has control over the modulation ofbeam intensity from one part of the target volume to another [L9]. Such intensity modulation can be
exploited in a manner similar to IMRT, as described earlier.

II. RECAPITULATION OF PREVIOUS UNSCEAR REPORTS
E10.
Radiation therapy involves the delivery of high absorbed doses to carefully delineated target
volumes for the treatment of malignant or benign conditions. Resources for radiation therapy are
distributed unevenly around the world, with significant variation in radiation therapy practice both
among and often within individual countries. In the 1990s, many cancer patients had little or no accessto radiation therapy services. Global annual numbers of complete treatments by the two mainmodalities, teletherapy and brachytherapy, were estimated from the scarce national survey data
available, supplemented using a global model, although the uncertainties in this approach were likely to
be significant. The world annual total number of treatments for 1991–1996 was estimated to be about
4.7 million, with teletherapy accounting for over 90% of the treatments [U6]. The corresponding
average annual frequency of 0.9 treatment per 1,000 population was similar to the level quoted for
1985–1990 on the basis of an estimated total number of 4 million treatments [U5].
E11.
Cancer is likely to be an increasingly important disease in populations with extending lifespan,
and this will probably cause radiation therapy practice to grow in most countries. The World HealthOrganization (WHO) estimated that by 2015, the annual number of new cancer cases worldwide would
rise to about 15 million, from nine million in 1995, with about two thirds of these cases occurring in
low-income countries. If half of these cases patients were treated with radiation, at least 10,000 externalbeam therapy machines would be required in addition to a large number of brachytherapy units.
E12.
In the period 1997–2007, the global use of radiation therapy increased to 5.1 million treatment
courses, from 4.7 million treatment courses in 1991–1996. About 4.7 million patients were treated withexternal beam radiation therapy, while 0.4 million were treated with brachytherapy. The number oflinear accelerator treatment units increased to about 10,000 worldwide, mainly in health-care level(HCL) I countries. HCL II countries appeared to show a decrease, but this was probably due to the lackdata. At the same time, the number of brachytherapy treatments and the number of after loadingbrachytherapy units appeared to have changed only very little [U9].
E13.
Radiation therapy involves the delivery of high doses to patients, hence with an attendantpotential for accidents with serious patient health consequences (arising from over- or underexposure
relative to prescription). Quality assurance programmes helped to ensure high and consistent standardsof practice so as to minimize the risks of accidents. Effective programmes comprehensively address all
aspects of radiation therapy, including (a) the evaluation of patients during and after treatment; (b) the
education and training of physicians, technologists and medical physicists; (c) the commissioning,calibration and maintenance of equipment; (d) the independent audits for dosimetry and the treatment
planning; and (e) the protocols for treatment procedures and the supervision of delivery.

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E14.
This section presents information on trends in the frequencies of radiation therapy courses
resulting from the submissions to the UNSCEAR Global Survey (2009-2018) also summarized inelectronic attachment E-1. Furthermore, the data presented here were supplemented with informationfrom reviews of the published literature.

A. UNSCEAR Global Survey data
E15.
Radiation therapy data were received from 49 countries, most of which provided “essential”
data, however, some of the data appeared to be unrealistic, possibly due to misunderstandings regarding
the data requested. The questionable data were highlighted in the evaluation. In several cases, the“essential” data provided were inconsistent with the “detailed” data provided. These data were also
identified in the sections below. In the “essential” questionnaire, the distinction was not made between
benign and malignant diseases, although this distinction was made in the “detailed” questionnaire. Only
10 countries provided detailed data on patient treatment frequencies although 34 provided total values.
The data provided by Member States were regrouped into 10-year intervals.
E16.
This evaluation also requested information on uncertainties, which was addressed by several
countries. Some countries reported large uncertainties in their data for the detailed frequency data:
Argentina 40%; Brazil, 50%; Finland, 35%; Lebanon, 60%; Philippines, 75%; Romania, 50%; andSwitzerland, 95%.
E17.
The figures and tables in this section illustrate the variations in availability of radiation therapy
services in different countries. While the data are relatively sparse, a number of conclusions have beendrawn that indicate differences among regions and countries and help to highlight those areas where thesmaller numbers of facilities and staff contribute to limitations in access to radiation therapy services.
Some data are also provided to illustrate differences in numbers of patients treated by country, which
also support conclusions drawn regarding access to radiation therapy in these countries. The quantity“courses of treatment” (or “treatment courses”) has been used rather than number of patients. A courseof treatment may consist of a single delivery of radiation, but it more often refers to a series of 20 or 30
individual treatments, called “fractions”. The quantity “courses of treatment” is used as an indicator of
the volume of work performed in radiation therapy centres and the availability of radiation therapy
resources in a country. In many cases, data on the numbers of courses of radiation therapy are reported
in relation to the population of each country, e.g., radiation therapy treatment courses per 100,000
population. However, the denominator chosen for radiation therapy is two orders of magnitude larger
than that for diagnostic radiology, due to the generally smaller numbers of radiation therapy patients.
E18.
In the figures and tables below, the data reported were used directly and without modificationfrom the results of the UNSCEAR Global Survey, with a few exceptions. Cancer incidence data werecited from the GLOBOCAN online database [I5] as of 2018. In a few cases, the total numbers oftreatment courses were inconsistent between the “essential” and the “detailed” data. In such cases, thevalue from the “detailed” spreadsheet was usually chosen, provided it was also consistent with theindividual values from which it was presumably summed. In a few cases, countries provided data for
specific parameters such as treatment site but did not provide the total number of treatments. In thesecases, the individual country data were summed to determine the total value. Some data provided by
Chile, Pakistan and the Russian Federation were not reported as they may have reflected the number oftreatment fractions rather than the number of patients treated.

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299

E19.
The annual number of courses of radiation therapy per population is an indication of acountry’s infrastructure, the access patients have to radiation therapy services, and the prevalence of
certain cancer types. However, it might also indicate societal philosophies regarding the treatment ofcancer or the recognition of radiation therapy as a viable modality for cancer therapy (table E1).
Table E1. Courses of treatment with brachytherapy or external beam therapy per year per 100,000
population
Brachytherapy treatment courses
per 100 000 population aExternal beam treatment courses
per 100 000 population

Argentina

3.8

52

Australia

11.6

263.7

Bangladesh

5.2

16.5

Belarus28.1

153

Belgium

18

309.7

Brazil9.2

118.4

Brunei Darussalam

0.0

60.3

Bulgaria

5.6

241.6

Canada

13.5

263.5

Country

China

66

Cyprus10

150.5

Czech Republic

9.3

160.7

Denmark

4.6

362.2

Estonia

11.6

163.6

Finland

3.7

296.1

France9.9

239.2

Germany437.2bGreece3.6

51

Hungary

25.7

175.2

Iceland

4.4

236.4

Iran (Islamic Republic of)

5.2

78.5

Italy

16.5

363.1

Japan

9.2

188.3

Lebanon

2.9

89.8

Lithuania

21.7

181

Luxembourg

5.7

244.8

Madagascar

0.0

0.6

Malaysia

5.5

38.1

Montenegro

12.7

183.2

Norway

5.1

245.1

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UNSCEAR 2020/2021 REPORT

Brachytherapy treatment courses
per 100 000 population aExternal beam treatment courses
per 100 000 population

Pakistan

1.4

5.3

Philippines

1.3

33.2

Poland

28.1

196.4

Romania

8.1

158.8

Russian Federation

10.6

289.9

Saudi Arabia

2.4

25.2

Spain

19.4

243

Country

Sudan

8.4b

Suriname

10.2

57.8

Sweden16.5

235

Switzerland

23.8

368.2

Thailand

25.2

63.4

Ukraine

0.4

12.8

United Arab Emirates

0.7

11

United Kingdom

8.6

222.9

United States

10.4

308.5

a

Zero values are indicated when available; otherwise, cells have been kept empty.

b

The country reported only the total number of radiation therapy patients, which includes patients treated for benign conditions

as well as those treated for malignancies. The reported number has been placed in the column for external beam patients.

E20.
While the number of treatment courses in a country is of interest, a better indication of theavailability of and access to radiation therapy may be the number of courses of treatment relative to theincidence of cancer in the country. Table E2 shows a comparison of these two parameters. The data forcancer incidence are taken from the WHO GLOBOCAN [I5] database as of 2018. The data arepresented as a percentage of cancer incidence. Figure E-I summarizes the countries participated in the
UNSCEAR Global Survey. When comparing some of the countries in the same regions, the numbers ofpatients treated were considerably higher. It is possible that these countries reported the number oftreatment fractions delivered, rather than the number of courses of treatment, which might increase thevalue by a factor of approximately 18, on the basis of the data provided by countries for numbers offractions delivered. However, several other countries (e.g., Indonesia, Madagascar and Ukraine)
reported very low numbers of treatments.

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301

Table E2. Number of courses of radiation therapy treatments delivered scaled by cancer incidence ineach country
Country

Cancer incidence(GLOBOCAN 2018) [I5]External beam and brachytherapy
treatment courses/cancer incidence (%)

Argentina

129 047

17.3

Australia

197 876

33

Bangladesh

150 78123

Belarus42 287

40.6

Belgium

79 931

46

Brazil559 371

46.6

Brunei Darussalam

908

28

Bulgaria

35 37848.9

Canada249 077

40.8

China

4 285 033

21.5a

Cyprus

4 829

31.6

Czech Republic

65 456

27.5

Denmark

40 79651.3

Estonia

7 664

29.9

Finland33 271

49.3

France455 618

36.1

Germany

608 742

58.3a

Greece67 401

8.9

Hungary

70 45428.2

Iceland

1 510

54

Indonesia

348 809

0.02

Iran (Islamic Republic of)

110 115

57.1

Iraq

25 320

11.3

Italy

409 808

56.1

Japan

883 395

28.4

Lebanon

17 294

10.5

Lithuania

16 35135.8

Luxembourg

3 271

41.9

Madagascar

18 0740.9

Montenegro

2 366

49.7

Norway34 29938.6

Pakistan

173 937

8.1

Philippines

141 021

24.7

302

UNSCEAR 2020/2021 REPORTCountryaCancer incidence(GLOBOCAN 2018) [I5]External beam and brachytherapy
treatment courses/cancer incidence (%)

Poland185 630

46.5

Romania

83 461

39.3

Saudi Arabia

24 485

43.6

Spain

270 363

45.3

Sudan

25 746

13.5aSuriname

1 042

36.4

Sweden60 853

41.3

Switzerland

56 506

58.4

Thailand170 495

34.5

Ukraine169 817

3.3

United Arab Emirates

4 707

23

United Kingdom

446 942

33.7

United States

2 129 118

48.4

Data provided include radiation therapy patients treated for benign as well as for malignancy conditions.

Figure E-I. Percentage of patients treated with radiation therapy per cancer incidence (GLOBOCAN
2018 data [I5])E21.
The UNSCEAR Global Survey data provided an opportunity to evaluate the frequency withwhich different cancers were treated with radiation therapy, in terms of the global population. Table E3
and figure E-II show these data for treatments with brachytherapy and external beam radiation. Not
surprisingly, patients treated for gynaecological cancer account for more than 60% of all patientstreated with brachytherapy, while prostate cancer accounts for more than another 15%. Breast, head andneck, lung and prostate are the sites most often treated with external beam radiation therapy.

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Table E3. Most frequently treated cancer sites and percentage of annual treatments withbrachytherapy or external beam therapy worldwide
Modality category

Brachytherapy

External beam

Cancer site

Percentage of treatments
worldwide (%)

Breast12.4

Colorectal

0.6

Eye

1.4

Gynaecological

64.3

Head/neck

0.8

Lung

0.6

Prostate

16.4

Skin

3.2

Bladder

0.9

Bone and soft tissue sarcomas

0.6

Bone metastases

3.5

Brain metastases

2

Breast27.2

Colon and rectum

4.4

Gynaecological tumour

5.9

Head/neck

9.9

Kidney (including Wilms' tumour)

1.2

Lung/thorax (including oesophagus)

15.2

Lymphoma/Hodgkin

0.7

Lymphoma/Non-Hodgkin

1.5

Primary brain

3

Prostate

14.2

Skin (local therapy)

2.3

Total body irradiation

0.1

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UNSCEAR 2020/2021 REPORT

Figure E-II. Percentage of diseases accounting for most radiation therapy treatments worldwide
The ordinate is expanded for clarity. Gynaecological disease accounts for 64% of all brachytherapy treatments

B. Literature review data
E22.
The incidence of cancer worldwide, in terms of absolute numbers, has been growing steadily
and is continuing to grow. In 2012, 14.1 million new cases of cancer were reported, and 8.2 million
deaths were caused by cancer. These numbers are expected to rise to 24.6 and 13 million, respectively
by 2030 [A12]. Except in high-income countries, the access to radiation therapy is extremely limited,
and for much of the world’s population, non-existent. This situation has developed because, according
to Atun et al. [A12] radiation therapy is rarely considered first when governments plan and build
treatment capacity for cancer. Instead, surgery and chemotherapy were addressed first, and radiation
therapy is too often relegated to last place. In low- and middle-income countries 80% of the cancer
burden occurs, however, have only 5% of the world’s resources. Consequently, more than 90% of the
population of low-income countries have no access to radiation therapy.
E23.
The Atun et al. study [A12] presented useful information based on the International Atomic
Energy Agency (IAEA) Directory of Radiotherapy Centres (DIRAC) database. DIRAC includes data of
the numbers of radiation therapy departments; and total numbers of megavoltage machines, linear
accelerators and 60Co units [P11]. Atun et al. [A12] modelled estimates of capacity (fractions per year),describing the estimated radiation therapy utilization rate, mean number of fractions per course oftreatment, and outcome benefits (absolute/proportional) for the top ten cancers globally by incidence.
Atun et al. [A12] also presented estimates of radiation therapy resources and modelled capacity andANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

305

estimated the cost and substantial benefits to the global community of expanding radiation therapy
resources. Some of these conclusions are echoed by Jaffray et al. [J3, J4] and Rodin et al. [R10].
E24.
Abdel-Wahab et al. [A1] published a comprehensive review of the IAEA activities in supportof radiation therapy worldwide. They quote a recent IAEA analysis of future needs for radiation
therapy, which determined that more than 50% of patients requiring radiation therapy in low- andmiddle-income countries do not have access to such treatments. As indicated by Atun et al. [A12], thesituation is even more drastic in low-income countries, where the proportion of patients requiringradiation therapy is higher than 90%. In terms of teletherapy equipment, an IAEA analysis showed that
4,300 machines are available in low- and middle-income countries but that 7,000 additional units areneeded to provide sufficient radiation therapy treatments. This situation is expected to improve in the
coming years however, a large proportion of patients needing radiation therapy will not have access tosuch treatments in the near future. The IAEA provides support for expansion of radiation therapy
services through the supply of equipment, provision of expert services, and fellowships for training ofhealth-care professionals.
E25.
Pan et al. [P3] published information regarding patient treatments in the United States basedon survey information conducted by the National Cancer Institute (NCI) in its Surveillance,
Epidemiology and End Results Program [S25]. The authors extrapolated on the basis of estimates of thefraction of the total number of radiation therapy patients in the United States covered by the surveys.
The authors emphasized that the NCI data reported only the frequency of each patient’s first course ofradiation therapy for a specific malignancy. However, as many patients have second (or more) courses,
this led to an underestimate of the number of courses of radiation therapy.
E26.
The NCI data excluded patients under palliative therapy rather than cancer cure treatments. As
a result, Pan et al. [P3] reported annual utilization rates of about half those reported to the UNSCEAR
Global Survey. The UNSCEAR data for the number of patients treated with external beam radiation
therapy in 2017 was 996,313, while Pan et al. reported only 490,000 in 2015. Pan et al. also reported
the number of patients by disease sites; however, which is also about half of the number reported to the
UNSCEAR Global Survey. Pan et al. [P3] summarized the utilization rate of radiation therapy to be
26%; about half the rate reported to the UNSCEAR Global Survey (48.4%).

IV. DOSES IN RADIATION THERAPY
A. UNSCEAR Global Survey data
E27.
Forty-nine countries provided data regarding patient doses to the UNSCEAR Global Survey.
In radiation therapy, parameters of great interest are the site treated, the total dose delivered, thenumber of treatment fractions delivered, and the treatment technique used.
E28.
The current survey data enabled examination of the therapeutic doses delivered to patientstreated for a number of different cancers, using the major treatment modalities. Unfortunately, too few
countries submitted data to make the analysis very expressive. Note that the UNSCEAR Global Survey
did not request information about imaging doses although they are increasingly being viewed as ofinterest in long-term.

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B. Literature review data
E29.
Comprehensive data regarding prescribed doses in radiation therapy are available in many
publications. A valuable source of information regarding doses from radiation therapy in the UnitedStates has been published by the NCRP [N1]. The report identifies some of the difficulties encounteredwhen trying to summarize doses from radiation therapy procedures. These include the wide variety inprescribed tumour doses, which are tailored to each individual patient, and may vary by an order ofmagnitude or more depending on the stage of the patient’s disease or the fractionation scheme chosen.
The doses to healthy organs also vary widely as the ability to protect these organs is profoundly
influenced by the extent of the cancer and the goals of the treatment. Further, the evolving technologyof radiation therapy has greatly affected the doses to normal structures and enabled the delivery ofgreater tumour doses. However, the NCRP [N1] estimated equivalent doses delivered to organs andtissues for ten broad categories of treatment site and from these derived estimates of collective effective
dose for external beam radiation therapy.

V. DISTRIBUTIONS BY AGE AND SEX

A. UNSCEAR Global Survey data
E30.
Figures E-III to E-VIII illustrate the variations in age of diagnosis for cancer patients treatedwith radiation therapy. Only a small number of countries reported such data. Figure E-III also shows
the age distribution for males treated for all cancers reported in the UNSCEAR Global Survey, for ninecountries. Large similarity is observed, with the exception of the Philippines, for which the numbers
reported did not seem to reflect the totals. Figure E-IV displays the age distribution data for female
patients, where the age distribution data are shown as a proportion of the total number of patients (maleand female) in each group.
E31.
Figures E-V and E-VI present the age distribution for male and female lung cancer patients,
respectively. Figure E-VII displays the age distribution data for male prostate cancer patients, while
figure E-VIII displays these data for female breast cancer patients. Due to the lack of the data, it is notpossible to draw firm conclusions, however, some differences were identified, such as the difference inage distribution for both male and female lung cancer patients among countries, and similar differences
for prostate and breast cancer patients.

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307

Figure E-III. Age distribution of male radiation therapy patients reported to UNSCEAR Global Survey

Figure E-IV. Age distribution of female radiation therapy patients reported to UNSCEAR Global
Survey308

UNSCEAR 2020/2021 REPORT

Figure E-V. Age distribution of male lung cancer patients reported to UNSCEAR Global Survey

Figure E-VI. Age distribution of female lung cancer patients reported to UNSCEAR Global Survey

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

309

Figure E-VII. Age distribution of male prostate cancer patients reported to UNSCEAR Global Survey

Figure E-VIII. Age distribution of female breast cancer patients reported to UNSCEAR Global Survey

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B. Literature review data
E32.
Relatively little data are available from the literature describing the distribution of radiation
therapy patients by age and sex. Where such data were published, the results do not indicate unusual
variations suggesting prevailing treatment of a specific age group or sex. Instead, variations reflect
differences in the incidence of specific cancers.

VI. STAFF AND DEVICES

A. UNSCEAR Global Survey data
E33.
Most countries provided the number of physicians registered in the country, including generalpractitioners, radiation oncologists and doctors, who use radiation but are not radiation oncologists(e.g., dermatologists or surgeons). In some countries, the number of registered physicians might belarger than the number who practice regularly; moreover, physicians who were identified as radiation
oncologists might also practice in other specialties such as medical oncology or general practice.
E34.
Table E4 presents the numbers of physicians per 100,000 population for all countries thatprovided data to the UNSCEAR Global Survey. Table E4 also shows the data for radiation oncologists
per 100,000 population. The numbers of radiation oncologists, where reported, are generally small incomparison with the total numbers of physicians, and the numbers of general practitioners. However,this is not surprising as radiation oncology is a relatively small specialty. Of more interest is thevariation in proportion of radiation oncologists between the countries reporting data.
E35.
The numbers provided showed a quite large variations, with Indonesia, Iraq, Madagascar,
Pakistan and Sudan reporting fewer than 0.1 radiation oncologists per 100,000 population, far less thanmost other countries. Chile reported very small numbers of both, but a smaller number of physicians
than of radiation oncologists. The United Arab Emirates indicated a small number of radiation
oncologists (0.1 per 100,000 population), but an overall number of physicians within a factor of 2
higher than most HCL I countries. Italy reported a number of total physicians per population that isabout double the average in Western Europe and North America (table E4). In contrast, Denmark
reported considerably more radiation oncologists per population than other Western European
countries. While some of these data might be debatable, they support the observation that populationsof high-income countries have more access to radiation therapy services than other parts of the world.
E36.
Variations in the numbers of radiation oncologists per population are not surprising. It is
common that these professionals have additional hospital roles in some countries other than the provisionof radiation therapy services. For example, radiation oncologists are involved in research, which might bemore prevalent for countries in Western Europe and North America than in other parts of the world. In
Asia, radiation oncologists sometimes also provide medical oncology services.

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311

Table E4. Physicians per 100,000 population reported to UNSCEAR Global SurveyCountry

Number of physicians per 100 000 population a
All physicians

General practitioners

Radiation oncologists

Argentina

388.9

0.5

Australia

347.5

Bangladesh

47.2

Belarus

481.8

481.8

1.4

Belgium

392.8

136.4

1.6

Brazil

217

20

0.4

108.2

1.5
0.2

Brunei Darussalam

0.2

Bulgaria

412.9

Canada

226.5

0.8
117.6

Chile

1.5
0.5

China

217.9

13.5

1.1

Cyprus

309.3

Czech Republic

393.2

49.2

1.5

Denmark

403.5

78.9

3.9

Estonia

361.8

69.8

1.5

Finland

493.4

32.2

0.8

France

333.7

154.9

1.3

Germany

369.5

Greece

276.8

62.5

1.8

Hungary

309

65.3

0.4

Iceland

401.7

Indonesia

81.3

Iran (Islamic Republic of)

110

Italy

654.7

Japan

244.9

Lebanon

285.8

285.6

0.3

Lithuania

442.5

72.9

0.9

Luxembourg

316.7

95

1.1

1.9

1.4

0.6
1.3

0.03
0.2

74.6

1.5
0.9

Madagascar

0.03

Malaysia

0.4

Montenegro

1.5

Norway2.6

Pakistan

94.6

0.07

Philippines

128.7

0.2

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UNSCEAR 2020/2021 REPORT

Number of physicians per 100 000 population aCountry

All physicians

General practitioners

Radiation oncologists

Poland

371.6

29.2

2

Romania

275.4

83.3

0.8

Russian Federation

371.6

47.9

0.1

Saudi Arabia

0.2

Spain

241.4

1.5

Sudan

10.6

0.05

Suriname

0.4

Sweden450

0.8

Switzerland

429.7

98.7

1.4

Thailand

87.4

33.7

0.2

United Arab Emirates

204.2

0.02

0.1

United Kingdom

59

57

2.1

United States

266.5

34.5

1.5

Population weighted
worldwide averagea

0.85

Empty cell indicates no data available.

E37.
In addition to the number of physicians, an indicator of the availability of radiation therapy
services in a country is the number of radiation therapy centres. This is shown for the countries
participated in the UNSCEAR Global Survey in table E5. Data are also extracted from the DIRAC
database [P11]. In many cases, there are differences between national data and the DIRAC database,and some of the differences are quite large. For this evaluation, the national data have been used whencountries reported more updated data than the DIRAC database.
Table E5. Radiation therapy centres as reported to UNSCEAR Global Survey and to DIRAC [P11]
Number of centres per 100,000 population are calculated from UNSCEAR Global Survey data
Country

Radiation therapy centres a
Current evaluation

DIRAC [P11]Per 100 000 population

Argentina

154

81

0.38

Armenia

2

2

0.07

Australia

76

98

0.32

Bangladesh

12

17

0.01

Belarus

18

12

0.19

Belgium

37

36

0.33

Brazil

259

213

0.13

Brunei Darussalam

1

1

0.24

Bulgaria

17

18

0.24

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATIONCountry

313

Radiation therapy centres a
Current evaluation

DIRAC [P11]Per 100 000 population

Canada

51

51

0.14

Chile

20

26

0.11

China

1 413

1 075

0.10

Cyprus1

2

0.11

Czech Republic

63

30

0.60

Denmark

7

8

0.12

Estonia

2

2

0.15

Finland

13

13

0.24

France

172

179

0.26

Germany

360

286

0.44

Greece

32

27

0.29

Hungary

12

13

0.12

Iceland

1

1

0.30

Indonesia

33

35

0.01

Iran (Islamic Republic of)

44

79

0.06

Iraq

12

11

0.04

Italy

193

191

0.32

Japan

788

766

0.62

Lebanon

12

13

0.25

Lithuania

4

5

0.14

Luxembourg

1

1

0.18

Madagascar

34

1

0.14

Malaysia

34

28

0.11

Montenegro

1

1

0.17

Norway

9

10

0.17

Pakistan

29

26

0.01

Philippines

36

36

0.04

Poland

44

41

0.11

Romania

21

25

0.11

Russian Federation

65

140

0.04

Saudi Arabia

13

14

0.04

Spain

149

127

0.32

Sudan

3

3

0.01

Suriname

1

1

0.18

Sweden

17

18

0.17

314

UNSCEAR 2020/2021 REPORTCountry

Radiation therapy centres a
Current evaluation

DIRAC [P11]Per 100 000 population

Switzerland

35

36

0.42

Thailand

35

33

0.05

TurkeyUkraine

51

51

0.12

United Arab Emirates

4

3

0.04

United Kingdom

59

70

0.09

United States

2 270

2 153

0.70

Population weighted
worldwide average
a

132

0.17

Empty cell indicates no data available.

E38.
While the number of centres in a country relative to its population is an indicator of access toradiation therapy, the UNSCEAR Global Survey did not provide information about distribution ofradiation therapy centres. Countries such as Canada and the United Kingdom have a small number ofcentres, but they are generally large and located in major population regions/cities. The United States
have a large number of very small centres, but these are typically located in large population areas andthere are regions with populations that are quite remote from the nearest radiation therapy centre.
E39.
Another indication of access to radiation therapy is the number of radiation therapy treatment
equipment. As part of the UNSCEAR Global Survey countries were asked to report the number of
specific therapy treatment equipment and the total number of radiation therapy systems and figure E-IX
presents the total number of equipment per 100,000 population by country. Western Europe and North
America generally report larger amounts of equipment than do other parts of the world. Smaller
numbers are seen in Latin America and Asia. It should be noted that countries may have interpreted theterm used in the questionnaire “all radiation therapy systems” differently. Some countries included lowenergy treatment systems and imaging systems dedicated to radiation therapy, while others did not. In
addition, the term “imaging systems” may have been interpreted to mean the on-board kV imaging
systems now included with many modern linear accelerators, in addition to conventional X-ray
simulators and computed tomography scanners.

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

315

Figure E-IX. Radiation therapy systems per 100,000 population

E40.
A relevant measure of radiation therapy quality may be drawn from the staffing at radiation
therapy centres. Considerable variation is seen and there is somewhat of an inverse correlation with thenumber of centres. For example, the number of radiation oncologists per centre is large in Western
Europe and Canada where are few, generally large, centres. In contrast, in the United States, the numberof radiation oncologists per centre is very small, consistent with the high number of small centres.
E41.
The trends are similar for radiation therapy medical physicists, with large numbers per centre
seen in Western Europe and Canada and small numbers in the United States. The small numbers seen insome countries in Eastern Europe, Latin America, and Asia may not be an indication of small facility
size but a reflection of the lower staffing levels in these countries. The relationship between staffing
and the size of a centre is examined in more detail below.
E42.
The type of equipment at radiation therapy centres is addressed in table E6 where the numbersof linear accelerators per 100,000 population are shown. Table E6 also shows the total number oftreatment and imaging systems per 100,000 population per country. This may be an indication not onlyof the amount of equipment, and therefore the access to treatment the population would have, but also
an indication of the modernity of the equipment, which could correlate with the quality of treatment.
Table E6. Linear accelerators and treatment and imaging systems in radiation therapy reported to
UNSCEAR Global SurveyCountry

Linear accelerators
per 100 000 population

Treatment and imaging systems
per 100 000 population

Argentina

0.25

0.39

Armenia

0.03

0.10

Australia

0.76

1.02

Bangladesh

0.01

0.02

Belarus

0.15

0.55

Belgium

0.85

1.09

316

UNSCEAR 2020/2021 REPORTCountry

Linear accelerators
per 100 000 population

Treatment and imaging systems
per 100 000 population

Brazil0.18

0.27

Brunei Darussalam

0.47

0.71

Bulgaria

0.41

0.75

Canada

0.76

0.78

Chile

0.21

0.32

China

0.14

0.19

Cyprus0.32

0.53

Czech Republic

0.44

1.06

Denmark

0.93

1.21

Estonia

0.45

0.61

Finland

0.82

1.02

France0.64

0.76

Germany

0.74

1.35

Greece0.35

0.59

Hungary

0.27

0.64

Iceland

0.59

0.59

Indonesia

0.02

0.03

Iran (Islamic Republic of)

0.03

0.08

Iraq

0.08

0.08

Italy

0.71

0.89

Japan

0.68

0.96

Lebanon

0.33

0.42

Lithuania

0.42

0.73

Luxembourg

0.73

1.10

Madagascar

0.01

0.01

Malaysia

0.17

0.28

Montenegro

0.17

0.50

Norway0.81

0.93

Pakistan

0.01

0.03

Philippines

0.04

0.07

Poland0.42

0.57

Romania

0.12

0.30

Russian Federation

0.14

0.63

Saudi Arabia

0.09

0.10

Spain

0.53

0.74

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATIONCountry

317

Linear accelerators
per 100 000 population

Treatment and imaging systems
per 100 000 population

Sudan

0.01

0.04

Suriname

0.36

0.54

Sweden0.73

0.97

Switzerland

0.84

1.75

Thailand

0.11

0.19

Turkey0.27

0.39

Ukraine

0.05

0.23

United Arab Emirates

0.08

0.12

United Kingdom

0.45

0.45

United States

1.11

1.11

Population weighted worldwide average

0.29

0.37

E43.
An indication of treatment quality (and availability of medical professionals) is the level ofstaffing per radiation therapy unit. Figure E-X compares the average numbers of radiation oncologists
and medical physicists per treatment system by country. All devices considered here were cobalt units,brachytherapy systems and simulators in order to assess the work volume per staff member.
Figure E-X. Radiation oncologists and medical physicists per radiation therapy centre

E44.
A different measure of patient access to radiation therapy is obtained by comparing the annual
number of patients treated per centre, taken as an average by country (figure E-XI). Several countries,
including Chile, Pakistan and the Russian Federation have been removed from the figure. These
countries reported data that yielded extremely high annual values of patients per centre, several inexcess of 10,000. In contrast, Indonesia reported an extremely small number of patients, which mightreflect a misunderstanding of the type of data requested but could also reflect the functional status of318

UNSCEAR 2020/2021 REPORT

equipment in the country. For comparison, and assuming an average of 18 treatment sessions per
patient (a figure calculated from UNSCEAR Global Survey data) delivered in five sessions per week, apatient volume of 1,000 patients per centre suggests roughly 70 patients on treatment each day.
Figure E-XI. Annual number of patients treated per radiation therapy centre reported to UNSCEAR
Global SurveyCountries with inconsistent data have been removed

E45.
Using the information in figure E-XI one step further, the annual number of patients treated
per radiation therapy machine is shown in figure E-XII. Even when several countries were excluded,
these values vary by more than an order of magnitude. Indonesia reported only annually 1.2 patients pertreatment machine, which probably indicates a misinterpretation of the data requested. Several othercountries reported small numbers, which might be an indication that some of the equipment reported to
be installed was not being used or was non-functional. In contrast, the Islamic Republic of Iran reported
706 patients per treatment machine, which corresponds to a patient load of roughly 50 patients treated
per day and machine. This is certainly conceivable but is large for an average value. The annual
average across countries (excluding some countries) is approximately 300 patients per machine. Chile,
Pakistan and the Russian Federation reported more than 2,000 patients per machine annually.
E46.
Another, even better, measure of workload is conveyed by the annual number of patients perradiation oncologist. These data are shown in figure E-XIII, where a country’s annual number ofradiation therapy patients is divided by the number of registered radiation oncologists. To put the datain perspective, and assuming that patients receive an average of 18 treatment courses, five days per
week, a volume of 100 patients per year would suggest that a radiation oncologist is supervisingtreatment of an average of seven patients per day. This is a very small number; one would expect aradiation oncologist in a busy practice to supervise up to 30 patients per day. In an academic practice,
the number might be reduced by half. The results suggested discrepancies in interpretation or reportingof data. In particular, Chile and the Russian Federation reported data to the UNSCEAR Global Survey
suggesting that the average annual number of patients per radiation oncologist is extremely high.

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

319

Figure E-XII. Annual number of patients treated per radiation therapy machine reported to UNSCEAR
Global SurveyCountries with inconsistent data have been removed

Figure E-XIII. Annual number of patients treated per radiation oncologists reported to UNSCEAR
Global SurveyCountries with inconsistent data have been removed

320

UNSCEAR 2020/2021 REPORT

B. Literature review data
E47.
The UNSCEAR Global Survey requested data on the number of staff working in radiation
therapy per country. In table E7, these data are compared with data from another survey conducted byInternational Organization for Medical Physics (IOMP) [T9]. It should be noted that IOMP reported
numbers of all medical physicists, not only radiation therapy physicists. The differences are quite
notable; in many cases, the value reported by IOMP is double or more than that supplied to the
UNSCEAR Global Survey. One explanation is that IOMP counted medical physicists working inradiology and nuclear medicine in addition to those in radiation therapy. Further explanation for thesedifferences might be that the UNSCEAR Global Survey asked government officials, or professionals
having access to national databases, to complete the survey and the source of national data in many
countries is most likely an official registry of licensed or otherwise credentialed individuals. On theother hand, IOMP contacted professional societies (in most cases, those affiliated with it), who may
have referred to membership databases.
E48.
Dad et al. [D2] discussed education and its role in improving cancer care worldwide. The
American Society for Radiation Oncology formed an international education subcommittee toencourage a movement towards a more region-speciﬁc, needs-based approach to closing the gap inradiation therapy services to low- and middle-income countries. These efforts are intended tosupplement ongoing global health initiatives with a focus on enhancing education and training in lowand middle-income countries through the use of modern information and communication technologies.
Areas that require special attention include encouraging trainees interested in global health as a future
career, addressing ethical issues that may arise in consideration of global health outreach, and using
political advocacy as a vehicle for change. The authors encouraged collaboration with the industry tohelp achieve the goals established by United Nations Political Declaration of the High-Level Meetingof the General Assembly on the Prevention and Control of Non-Communicable Diseases in 2011
[G18]. There is an increased need for educational resources for medical physicists in many low- andmiddle-income countries, which contributes to the scarcity of radiation therapy in these countries [V1].
Collaboration between high income and low- and middle-income countries is therefore necessary [W8].
Table E7. Number of medical physicists reported to UNSCEAR Global Survey and IOMP [T9]
Data from UNSCEAR Global Survey includes radiation therapy physicists only while data from IOMP [T9]includes all registered medical physicists in a country
Country

Current evaluation

IOMP [T9]Argentina

133

167

Australia

450

717

Belarus88

Belgium

145

215

Brazil303

732

Brunei Darussalam

43Bulgaria

68

84

Canada

411

726

China

3 294

1 600

Cyprus6

60

Czech Republic

89

147

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATIONCountryaCurrent evaluation

IOMP [T9]Denmark

82

178

Estonia

13

Finland

47

127

France556

520

Greece86459

Hungary

64

96

Indonesia

58

Italy

600

1 016

Japan

388

958

Lebanon19

20

Lithuania

1220

Luxembourg

5

Norway74

186

Philippines

60

110

Poland425

210

Romania

48

134

Russian Federation

270

600

Spain

513

837

Sudan

12

28

Sweden148

300

Switzerland

80

216

Thailand

134

150

United Arab Emirates

1235

United Kingdom

698

1 700

United States

3 405

8 849

Totala12 89429 179321

Not necessarily the sum of all columns.

E49.
Several authors have addressed specific needs in low- and middle-income countries, such as
the scarcity of modern treatment planning and treatment delivery techniques. Falahatpour et al. [F1] has
investigated the use of 2D planning systems in comparison to 3D planning. The use of 2D planningsystems could allow both high and low dose regions to occur in the treated volume as compared with
3D planning. The significance of low dose regions within the treated volume cannot be overstated as it
causes a measurable reduction in tumour control probability. Retrospective studies have indicated that a
reduction in breast dose from 50 to 45 Gy can lead to a reduction in local control from 95 to 85% whendifferences in fractionation and tumour size are considered [A11].
E50.
Redmond et al. [R2] pointed out that as cancer survival increases with improvement insystemic therapy, localized treatment such as radiation therapy, and immunotherapy, achieving durable
local control of metastatic spinal disease will become increasingly important. In addition, as patients

322

UNSCEAR 2020/2021 REPORT

live longer, the risks of treatment will need to be mitigated as the opportunity for toxicity to present
during a patient’s lifetime will be greater. Continued advances in technology in the near future willallow increasingly precise treatment delivery.
E51.
Grover et al. [G15] reviewed the role of brachytherapy and the barriers to providing both lowdose rate (LDR) and high dose rate (HDR) brachytherapy in low- and middle-income countries.
Cervical cancer is the fourth most common cancer affecting women worldwide. However, 90% ofcervical cancer deaths occur in low- and middle-income countries, making it the leading cause ofcancer-related deaths in women in these countries.
E52.
Data are available for some specific regions and countries. For example, data on cancer andaccess to radiation therapy in South America have been described by Amendola et al. [A4, A5]. They
conducted surveys in each country and reported the results in several publications. South Americancountries have different issues with access that depend on their economies, geography and social
system. With a population of about 44 million in 2016, Argentina is the third most populous country inSouth America. According to Amendola et al., the country has 150 radiation oncologists and
60 medical physicists, falling short of IAEA recommendations [I2] for 180 radiation oncologists and
120 medical physicists. According to the DIRAC database [P11], there are currently 81 radiation
therapy centres in the country, which together have 87 linear accelerators and 31 cobalt units.
Radiosurgery, IMRT and brachytherapy are available in only a few centres. There are currently twocyberknife facilities. Even given the number of centres available, access for much of the population isrestricted because the majority of the centres are private not accessible to everyone [A5].
Approximately 90% of the population have either no health insurance at all, or are covered by one ofseveral public programmes, meaning that they have access to only 20% of radiation therapy centres(roughly 17) that are publicly owned. The government has recently implemented a plan to improvecancer care, and in 2015 signed an agreement to install a proton therapy centre.
E53.
Brazil is the largest country in South America in terms of both geographic area and population.
According to Amendola et al. [A5], in 2013 only about 28% of the population had health insurance.
The remaining population relied on the public health care services. The government’s goals of universal
health care access have not been met. Cancer, requiring high-complexity treatment, is to be handled at
the federal level. But the mechanisms to refer patients to centres where they can receive treatment are
not developed. Amendola et al. [A5] estimated that, according to WHO guidelines for radiation therapy,
more than 100,000 patients did not receive treatment in 2010 due to the lack of infrastructure. A federal
initiative in 2014 was intended to fund the purchase of 80 linear accelerators but, according toAmendola et al., many of those units were yet to be installed in 2017, and the training and education to
support the services were going to depend heavily on industry support. As of 2012, there were
314 linear accelerators and 62 cobalt units registered as operational in Brazil, or roughly one per557,000 population. Most of these, and also many of the radiation oncology professionals, are locatedin the major population centres, leaving much of the sparsely populated regions with limited services.
E54.
Chile is one of Latin America’s more prosperous countries, with a relatively high per caput
income, and a large governmental health care expenditure. About 80% of the population is covered by
the public health care system, while those with higher incomes mostly have a private insurance.
According to the DIRAC database [P11], there are 18 radiation therapy centres in the country with
34 linear accelerators. Amendola et al. [A5] reported that the country has an uneven geographic andeconomic distribution of radiation therapy centres, most of which are in populated urban centres, suchas Santiago de Chile, and are mostly private.
E55.
Colombia is second only to Brazil in the size of its population, with nearly 49 million as of2016 [A5]. However, it has only 51 radiation therapy centres, with a total of 68 linear accelerators

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

323[P11]. More importantly, its economy is less buoyant, resulting in limitations on access to health carefor most of the population.
E56.
According to Amendola et al. [A5], Peru has the third largest geographic area and the fourthlargest population with about 32 million inhabitants. It is a relatively prosperous country, with 77% of
the population living in urban areas. In 2007, the country had only two radiation therapy centres, butthat number has increased recently and there are presently 19 centres, with 34 linear accelerators.
E57.
Despite a quite advanced economy and an educated population, Uruguay has a high rate ofcancer deaths, second only to the death rate from heart disease [A5]. In 2005, the Uruguayan
government created a National Program for Cancer Control with the goal of improving cancer care andintegrating the existing resources for care. Consequently, most of the radiation oncology centres arepart of a government network, leaving only a few that are privately operated. Several centres specialize
in cancers of a few clinical sites. According to a recent survey, 59.6% of the Uruguayan population
have private, commercially available insurance with different plans; 30.5% use public health services;and 7.2% qualify for government assistance on the basis of income level. The remaining 2.5% have noinsurance coverage, even though public health services are provided. In 2015, there were reported to be
14 linear accelerators, of which eight were in the private sector. Uruguay has one linear accelerator for
every 239,000 population, ranking high among high-income countries.
E58.
Goss et al. [G10] studied the status of radiation therapy and the access of cancer patients in
Latin America. The South American countries, for the most part, are quite underserved in terms ofradiation therapy services. In most cases, this stems from economic difficulties and low educationlevels. According to the study, the Latin American countries are currently overwhelmed by thechallenge of cancer control. The authors reported that the annual incidence of new cancers is estimatedto increase by 33.3%, to around 16.8 million cases by 2020. Without proactive planning, the increasing
cancer incidence will severely tax the resources of the region. Goss et al. [G10] encourage prompt
action to avoid dire human and economic consequences. Nicaragua, for example, has only two cobalt
units to serve its population of 6.2 million, while El Salvador has a slightly larger population of
6.4 million with access to four linear accelerators and four cobalt units.
E59.
A study of the cancer care provided to children in Mexico was undertaken to evaluate whether
a government programme to provide funding resulted in increased coverage for cancer care (including
radiation therapy) for children and adolescents [P6]. This population was adversely affected by a lackof support for treatment, especially among those not covered by the government social security healthprogramme. This publication reported that after four years, funding had been made available to support
cancer treatment for approximately 50% of the paediatric cancer cases without social security. The
report was not able to determine if there was an increase in the provision of cancer care (i.e., thenumber of paediatric cancer units). However, it was presumed that hospitals increased their capability
to be certiﬁed for this programme and receive the available funds. While the actual number of children
treated may not have increased, it was clear that the cost of care shifted from the parents or otherfunders to the government programme, thus reducing the number of out-of-pocket payers.
E60.
In Africa, in particular, there are very challenging issues regarding access to radiation therapy[B5]. As Atun et al. [A12] and Abdel-Wahab et al. [A1] have indicated, Africa faces an impending
cancer crisis. Many countries lack the resources to fund equipment and maintenance or deﬁcits ininfrastructure, human resources and training. Addressing these issues will be crucial to tackling theincreasing burden of cancer on the continent. There is a need for sustained government involvement
and consistent funding. As one example, among African countries, Nigeria boasts the continent’s
largest population (191 million) and the largest economy, although the gross domestic product per
caput ranks lower than other African countries [I19]. But, perhaps due to communication difficulties,

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UNSCEAR 2020/2021 REPORT

the DIRAC database lists only two radiation therapy centres, one with a single operational cobalt unit,
and one with a single operational linear accelerator [P11]. According to Irabor et al. [I19], the situation
may be slightly better, as the authors list nine cancer centres having a total of five linear accelerators,
two cobalt units and a few other pieces of radiation therapy equipment.
E61.
In most parts of Europe, as in North America, radiation therapy facilities are sufficient in
number and quality to address the needs of most of the population [R11]. However, there are regions inwhich the availability is limited, or the quality is inadequate. In Europe, a number of publications haveattempted to analyse the current and future demand for radiation therapy. For instance, Borras et al.
[B23] have evaluated the “optimum utilization proportion” of patients who should receive radiation
therapy in four European countries. In addition, Borras et al. [B24] have estimated the number ofpatients who will need radiation therapy in Europe in 2025. Grau et al. [G12, G13] have reviewed
radiation therapy services in Western European countries and claim that centralized cancer centres are
more efficient and of higher quality in Europe than the decentralized centres found in some othercountries, including the United States.
E62.
The Health Economics in Radiation Oncology (HERO) project of the European Society forRadiotherapy and Oncology have the overall aim of developing a knowledge base of the provision ofradiation therapy in Europe and building a model for health economic evaluation of radiation treatments[P9]. Lievens et al. reported on the personnel data collected in the HERO database [L4], on theavailability of equipment and staffing [L5], and on evidence from the existing expense literature [L7].
The papers discuss how such data can be used to support reimbursement setting and investment cases
for new radiation therapy equipment and infrastructure in Europe [L6]. It is noteworthy that the HERO
project collected data from national professional organizations and not governments.
E63.
Dunscombe et al. also reported on the equipment and staffing in European countries, where
people generally have good access to radiation therapy [D12]. The paper offers an estimate of thenumber of patients treated per machine based on the HERO Consortium survey. In Europe, the numberof courses of treatment per treatment machine varies from high values of 610 in Poland and 580 in the
Czech Republic, to low values of 330 in Denmark and 320 in Switzerland. Among the nine countries
providing data for the HERO project, the average value was 450 courses (patients) per machine per
year. According to the DIRAC database [P11], the approximate number of treatment machines (linear
accelerators plus cobalt-60 units) available worldwide is 14,285. Therefore, the worldwide capacity forradiation therapy patients can be estimated crudely as about 6.4 million courses of treatment per year.
E64.
This figure for capacity can be compared with an estimate of demand for radiation therapy
services. The global cancer burden has been estimated by WHO as 18 million new cancer cases in 2018
[I5]. Atun and others have estimated that 50% of cancer cases can benefit from radiation therapy; afigure that is supported by UNSCEAR Global Survey data for countries in Western Europe and theUnited States (table E2). Thus, in 2018, approximately nine million cancer patients could have been
expected to benefit from radiation therapy while, as of 2017, the worldwide capacity appears to havebeen approximately 6.4 million. There are many reasons for the observed differences: (a) while the
DIRAC database reflects the number of operational treatment units installed, the data do not indicate
the availability of service or the downtime experiences with the equipment; therefore, the treatment
capacity might be overstated; and (b) as can be seen from the UNSCEAR Global Survey, theutilization rates for radiation therapy equipment can vary considerably (figure E-XII). Moreover,while the distribution of treatment equipment is important, the availability of trained and qualified staff
is also relevant.
E65.
The situation in Eastern Europe is very challenging. Esiashvili [E8] has described progress inEastern European countries to update their facilities. The cancer burden in Eastern Europe is affected

ANNEX A: EVALUATION OF MEDICAL EXPOSURE TO IONIZING RADIATION

325

mainly by the population density, which is becoming increasingly heterogeneous. Cancer mortality
varies between countries and is influenced by multiple factors, including socioeconomic conditions,organization of health-care services, lifestyle and cultural differences. Overall, there is paucity ofradiation therapy services in Eastern Europe, and a severe lack of trained and qualified staff. Atun et al.
[A12] pointed out that low- and middle-income countries that wish to improve their radiation therapy
access for patients need to consider cost effectiveness as it applies to the health care system.
E66.
The HERO project asked participating organizations to report on staffing of radiation therapy
departments [D12]. A comparison between the HERO data and the UNSCEAR Global Survey reveals
quite similar results, as shown in table E8, with some notable exceptions. The data for physicists inseveral Eastern European countries are very different and might reflect the differences in the ways
medical physicists are counted by different surveys. For several countries, the ratios of patients perradiation oncologist are quite different in the HERO and the UNSCEAR surveys, possibly reflecting
differences in recording time spent in other activities such as academic work or treating patients withmodalities other than radiation therapy.
Table E8. Numbers of radiation oncologists and medical physicists expressed in relation to thenumbers of patients (courses of radiation therapy treatment)
Country

Number of patients per radiation oncologist
Current evaluation

HEROa

Current evaluation

Belgium

220

204

300

253

Czech Republic

130

115

580

202

88

210

176

Estonia
France

280

197

360

296

Hungary

220

496

330

310

Lithuania

170

225

200

488

Luxembourg

240

228

290

274

110

770

203

230

412

Polanda

Number of patients per medical physicist

HERO

a

Switzerland

170

275

United Kingdom

210

113

216

Values indicated as from the HERO project published by Dunscombe et al. [D12].

E67.
Countries in Southeast Asia face unique challenges. In the Philippines, Calaguas and Gubat[C1] have published data on issues limiting the population’s access to radiation therapy. Calaguas andGubat noted that external beam radiation therapy can be delivered safely and accurately using cobalt
and simple accelerators in most places where there currently are no radiation therapy facilities. The
authors argue that there is still a place for cobalt units, as their demands on resources are smaller andthey are more resistant to issues that cripple linear accelerators, such as unreliable water and electricity
supply. According to the DIRAC database [P11], there are currently 34 linear accelerators and four
cobalt units in the Philippines. Moreover, radiation therapy needs skilled and qualiﬁed humanresources. There appears to be a need for more educational and training activities in the Philippines.

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UNSCEAR 2020/2021 REPORT

E68.
Gondhowiardjo et al. [G8] published a review of status of radiation therapy and access tocancer patients in Indonesia. Much has been achieved in its 80-year history of radiation therapy, and theachievements in the last four years have been substantial. In a recent report, Gondhowiardjo et al. [G9]stated that as of 2019, there were a total of 66 megavoltage machines installed. The DIRAC databaselists 33 linear accelerators and 14 cobalt units in Indonesia, suggesting that recent installations might
not yet have been reported to the IAEA [P11]. Even with the recent increase in megavoltage equipment,
this number is insufficient for Indonesia’s population of more than 260 million. Shortages in radiation
therapy services, such as in brachytherapy, indicate that further improvements are needed.
E69.
In contrast, Singapore offers its population of 5.7 million 24 modern linear accelerators and anumber of advanced technologies including IMRT [T4]. Japan is considered an advanced country witha robust economy and a well-educated population. Its 127 million inhabitants have very good access to
798 radiation therapy centres with a total of 860 linear accelerators and 66 cobalt units, according to the
DIRAC database [P11]. Very advanced equipment is available, including proton therapy and carbonion therapy, as described by Kamada et al. [K2].
E70.
In Asian countries, Coburn et al. [C10] identified a correlation between survival of gastriccancer with lower stage, lower grade, positive marital status, Asian ethnicity, younger age, lower
T-stage, distal gastrectomy, female sex, and larger number of lymph nodes retrieved. There are clear
implications for low- and middle-income countries in which staging, lymph node dissection and othergood pathology practices are likely to be inadequate.
E71.
The utilization of radiation therapy in the Republic of Korea has been analysed recently by
Kim et al. [K9]. In the Republic Korea were 90 radiation therapy centres in 2015, containing 213
megavoltage treatment machines, including 196 linear accelerators, one proton accelerator, and 19
radionuclide units; and 31 remote brachytherapy afterloading devices. In 2016, 72,563 patients weretreated with radiation therapy. The most frequent cancers treated were breast, lung, colorectal, liver andprostate. In 2015, the country’s resources allowed a workload of an average of 310 patients per
megavoltage radiation therapy unit. Korea’s centres were relatively well staffed meaning that the
average radiation oncologist treated 246 patients while each physicist was responsible on average for501 patients.
E72.
Goss et al. reviewed the status of cancer care and access to radiation therapy in China, India
and the Russian Federation [G11]. They reported that cancer control in these countries must be
addressed to avoid increases in human suﬀering and future economic eﬀects. With its enormous
population, China has 1,131 linear accelerators and 538 cobalt units, roughly one treatment unit forevery 850,000 people [W3]. Clearly, more development and investment are needed here [W5]. India,
with one billion inhabitants, has only 260 linear accelerators and 346 cobalt units, mostly in a few
major population centres. And according to the DIRAC database [P11], the Russian Federation has 194
linear accelerators and 245 cobalt units for a population of 144 million. Further data and review
regarding the likelihood of improvement in the public health system in the Russian Federation has been
discussed by Jakab et al. [J5] and by Jargin [J7].
E73.
In India, more than 1.5 million new cancer cases occur each year [A12, G14]. Following
contemporary standards, more than 60% of these patients would benefit from radiation therapy, but thecountry is severely under-equipped and is likely to remain so well into the foreseeable future. There areseveral challenges in delivery of quality radiation therapy in India, which include lack of adequate
infrastructure and availability of adequate radiation therapy professionals. Despite these challenges,
there are ongoing efforts geared towards improvement of radiation therapy. These include increased
investment in health and cancer care by the government, initiatives by cancer centres in India to acquire
and improve their facilities, commitment by the government bodies to promote research and expansion

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327

of cancer centres, and efforts by national and international cancer societies to promote education andtraining of radiation professionals. Such changes are necessary to ensure that access to health care isavailable to all people in India, irrespective of their socioeconomic status [M5, P10]. Nepal has fivelinear accelerators and two cobalt units to serve a population of 29 million [G17].
E74.
An effort to address the status and resources for staffing in the Asia-Pacific region was
conducted by Kron et al. [K16]. The authors focused on the education, staffing levels and working
conditions of medical physicists in the region. While there were similarities, there were also starkdifferences between countries. For example, according to the survey described in this annex, thenumber of megavoltage treatment machines varied from 0.13 in Indonesia to 7 per million population in
Japan. Similarly, the number of radiation therapy patients per radiation oncology medical physicist
varied from 2,000 in Sri Lanka to 250 in Taiwan, China.
E75.
The United States is considered to have excellent resources for health care. According to the
DIRAC [P11] and the Imaging and Radiation Oncology Core databases [I21], there are at least 3,600
linear accelerators and a few (128) cobalt units, for approximately one megavoltage unit per 88,000
population. However, as reported by Guadagnolo et al. [G16], the provision of cancer care in general,and particularly radiation therapy, for native American and Alaskan populations, falls below that foundelsewhere in the country. In contrast, the use of advanced technologies has grown rapidly in most areasof the United States, and most Americans have access to these technologies. The growth of the use of
IMRT has been described [M4], and also its use for treatment of lung cancer [S13] and for breast
cancer [S20].
E76.
Still, there is evidence that the type of cancer treatment offered to some populations in the
United States, depends on their distance from a radiation therapy centre [S10]. The distance from thepatient’s home to the nearest radiation therapy facility was independently associated with breast cancer
surgical therapy in the state of Virginia, which is characterized by a diverse rural and urban population.
The relationship between longer distance to the nearest radiation therapy facility and higher
mastectomy use was independent of tumour size, year of diagnosis, and patient age and race.
E77.
In Canada, radiation therapy services are centralized at a few large and well-equipped centres.
This implies large distances between rural populations and cancer care services. Lower radiation
therapy utilization rates among elderly and out-of-area patients were determined by Wu et al. [W12].
The authors concluded that a simple referral pathway such as a community liaison provided by apalliative care nurse, and the judicious use of single-fraction therapy might increase the use of palliative
radiation therapy.

VII. TRENDS
E78.
Kilburn et al. [K7] identified a trend towards greater sparing of normal tissues and improved
conformity with the target volume. This trend is made possible by the increase in technologicalsophistication of treatment delivery; specifically, in the use of image guidance and delivery techniquessuch as IMRT, VMAT, particle beams and stereotactic techniques.
E79.
The trends in improved geometrical targeting have been accompanied by one towards higher
tumour doses, or higher dose per fraction combined with a smaller number of fractions [M15]. Thesechanges recognize the reduced doses delivered to normal tissues, enabling an escalation of tumour dose.
Kilburn et al. demonstrated that the use of image guidance has allowed radiation oncologists to become

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UNSCEAR 2020/2021 REPORT

more comfortable delivering higher doses, thus achieving greater tumour control without an increase innormal tissue toxicity [K7].
E80.
In brachytherapy, there is a trend away from LDR implants towards HDR single-fraction or
fractionated implants. For many diseases, HDR allows better conformity of the high-dose region withthe target volume as the treatment planner can optimize the locations and dwell time of the source.
E81.
Another trend involves the increase in multidisciplinary cancer therapy. While the use of
combined therapies such as surgery or chemotherapy with radiation has been in place for decades,
improvements, especially in drugs, have led to greater use of combination therapy. Data from clinical
trials continue to inform the use of radiation therapy. Today, there is a greater emphasis on evidencebased medicine bringing the expectation that treatment techniques will be used outside research studies
only if previously such studies have demonstrated value.
E82.
A major challenge in radiation therapy is to avoid delivering radiation doses to healthy tissues
that could create second malignancies in those tissues. Estimating the risk of second malignancies incancer patients is confounded because cancer patients have an increased risk of a second cancer due togenetic predisposition, environmental or lifestyle factors. It is known that chemotherapy increases risk,
especially of bone marrow related malignancies. The Committee recognizes the importance of second
malignancies following radiation therapy and has commenced an evaluation which will address thedosimetric, biological and epidemiological aspects pertaining to the risk of second primary cancer afterradiation therapy.

VIII. SUMMARY
E83.
In the period 1997–2007, the global use of radiation therapy increased to 5.1 million treatment
courses, from 4.7 million treatment courses in 1991–1996. In the period 2008–2018, a further increasein global use of radiation therapy was seen to approximately 6.2 million treatment courses. More than
5.8 million patients were treated with external beam radiation therapy, while about 0.4 million weretreated with brachytherapy. The number of linear accelerators increased to more than 12,000 worldwide
from about 10,000 in the previous period, and 5,000 in 1997–2007. A large increase was seen in HCL I
countries. At the same time, the number of brachytherapy treatments and the number of after loadingbrachytherapy units appeared to have changed very little, as was the case during 1997–2007. Particlebeam therapy facilities have been developed worldwide, with the result that today there are 104 particle
beam facilities in operation (carbon-ion facilities are counted independently of proton beam facilities).
Another 41 centres are under construction, while 27 are believed to be in the planning stages [P11].
E84.
Radiation therapy has undergone an evolution in the past several decades, with radical changes
in available treatment equipment and radiation beam modalities. Treatment techniques also haveadvanced considerably. In the past two decades, stereotactic treatment has progressed from being an
exceptional procedure available at only a few highly-specialized centres to widespread use in many
locations, due to the availability of immobilization and positioning devices. IMRT is used today for atleast half of the patients treated in centres in high-income countries and is being introduced in low- andmiddle-income countries.
E85.
Image-guided radiation therapy has similarly undergone a rapid increase in use, due to theavailability of kV imaging equipment on virtually all new medical linear accelerators. In high-income
countries, it is rare for a patient to be positioned for treatment without the use of orthogonal kV X-ray

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329

images, or cone-beam computed tomography scans. Image-guided radiation therapy is also being
introduced in low- and middle-income countries when equipment is replaced or upgraded. The use of
MRI for treatment guidance is currently being introduced at a few centres with possibly a dozen MRIlinear accelerators installed and undergoing testing or clinical use.
E86.
In many parts of the world, however, access to radiation therapy is extremely limited, and formany cancer patients who could benefit from treatment, it is unavailable. Low- and middle-income
countries rarely consider radiation therapy when planning cancer treatment facilities, instead focusing
on surgery and chemotherapy. Even in many high-income countries, poorer outcomes are seen inlocations where patients must travel great distances to the nearest radiation therapy centre. In most lowand middle-income countries, radiation therapy is available to very few patients, in most cases simply
because there are too few facilities to treat the patients. In some countries, there are no facilities. Evenin the more prosperous low- and middle-income countries, radiation therapy is unavailable to many
cancer patients who rely on social programmes because government funding for public services isrestricted and, for the most part, radiation therapy services are available only at private hospitals.

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This publication contains:
VOLUME I
Report of the United Nations Scientific Committee on the Effects of Atomic Radiation to
the General Assembly
Annex A: Evaluation of medical exposure to ionizing radiation

E VA L U AT I N G R A D I AT I O N S C I E N C E F O R I N F O R M E D D E C I S I O N - M A K I N G
In 1955 the United Nations General Assembly established the Scientific Committee on the Effectsof Atomic Radiation (UNSCEAR) in response to concerns about the effects of ionizing radiation
on human health and the environment. At that time fallout from atmospheric nuclear weapons
tests was reaching people through air, water and food. UNSCEAR was to collect and evaluate
information on the levels and effects of ionizing radiation. Its first reports laid the scientific grounds
on which the Partial Test Ban Treaty prohibiting atmospheric nuclear weapons testing was
negotiated in 1963.
Over the decades, UNSCEAR has evolved to become the world authority on the global levels
and effects of exposure to ionizing radiation. UNSCEAR’s independent and objective evaluationsof the science are to provide for—but not address—informed policymaking and decision-making
related to radiation risks and protection.

V. 21-09154

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