Diagnostic Reference Levels
Based on Latest Surveys in Japan—Japan DRLs 2015—

Japan Association on Radiological Protection in Medicine
Japan Association of Radiological Technologists
Japan Network for Research and Information on Medical Exposure
Japan Radiological Society
Japan Society of Medical Physics
Japanese Radiation Research Society
Japanese Society for Oral and Maxillofacial Radiology
Japanese Society of Nuclear Medicine
Japanese Society of Nuclear Medicine Technology
Japanese Society of Pediatric Radiology
Japanese Society of Radiological Technology

In collaboration withThe Japan Medical Imaging and Radiological Systems Industries
Association and the National Institute of Radiological Sciences

Preface
In recent years, concern regarding the effects of radiation exposure in medical care has
increased with the rapidly expanding use of medical radiation. Patients exposed to radiation indiagnosis or treatment gain clear benefits because the proper use of radiation can help
overcome potentially life-threatening diseases; therefore, the application of radiologicalprocedures should be judged on a case-by-case basis rather than by applying uniform
standards, such as dose limits. However, in actual practice, the top priority is to solve thehealth problems of the patient, and it is not always easy to optimally minimise the risks ofharmful effects that may occur in the future as a result of radiation exposure.
To cope with the growing issue of medical exposure, international organisations, such as
the United Nations Scientific Committee on the Effects of Atomic Radiation, International
Commission on Radiological Protection, International Atomic Energy Agency and World
Health Organization, have cooperated to achieve evidence-based protection from medical
radiation. One such measure is the application of diagnostic reference levels (DRLs) to
optimise protection. Currently, the establishment of DRLs is an international requirement forprotection from medical radiation.
Japan is facing a unique situation; the use of radiological examinations is rapidly increasing,whereas societal concern regarding the potential adverse radiation effects on human health isextremely high. Accordingly, protective measures should be implemented as rapidly as
possible. To this end, cooperation between academic societies and organisations is required toconcentrate the professional expertise of many experts, to collect and share information on
medical radiation exposure from within and outside of Japan and to establish a framework forprotection from medical exposure that fulfils the needs of the Japanese people. To conduct
such activities, the Japan Network for Research and Information on Medical Exposures(J-RIME) was established in 2010 with the cooperation of related academic societies.
The purpose of the J-RIME is to collect data related to medical exposure (i.e. radiation doseand risks received by radiological procedures), to address the actual state of medical exposurein Japan and to construct a framework within Japan for appropriate protection from medical
exposure based on international trends. As of 2015, the J-RIME has functioned as anationwide network with the participation of academic organisations of radiological sciences,including learned societies, universities, professional associations and medical facilities alongwith cooperation from administrative and related industrial organisations.
The J-RIME has established the first DRLs in Japan as a result of discussions with various
experts, including physicians, radiological technologists and medical physicists, based on the
results of the latest nationwide surveys conducted by liaison organisations of the J-RIME andthe advice from experts belonging to international bodies. This report for DRLs, called Japan
DRLs 2015, was approved for publication by the J-RIME and its liaison organisations in June
2015. The J-RIME will promote better understanding, expanded use and deeper permeation of
DRLs in medical settings while offering advice regarding expanding target modalities,
infrastructure development for the review of DRLs at certain intervals and incorporation into
domestic regulation systems.
Finally, I extend my heartfelt gratitude to all related individuals and parties for the time andeffort devoted to the dose surveys and preparation of this Report.
Yoshiharu Yonekura, MD, PhD
Chair, Japan Network for Research and Information on Medical Exposure;President, National Institute of Radiological Sciences

Contributors to drafting, review and performing dose surveys
ABE, Koichiro

ISHIGUCHI, Tsuneo

MEGURO, Yasuhiro

SATO, Kenji

ABE, Shuji

ISHII, Kazunari

MIYAGAWA, Kiyoshi

SATOH, Hiroyuki

AKAHANE, Keiichi

ITAMI, Jun

MIYAZAKI, Osamu

SATOH, Kimihiko

AKAHANE, Masaaki

ITO, Tomohiro

MOROZUMI, Kunihiko

SEI, Tetsuro

ASADA, Yasuki

IWANAGA, Akio

MURAMATSU, Yoshihisa SHIMADA, Yoshiya

AWAI, Kazuo

IZAWA, Maki

NAKAMURA, Kazumasa SHISHIDO, Fumio

AWAI, Kazuo

KAI, Michiaki

NAKAMURA, Yoshihide

SUZUKI, Shoichi

BAN, Nobuhiko

KANDA, Reiko

NEGISHI, ToruSUZUKI, Yoshiaki

DOI, Tsukasa

KATO, Kyoichi

NISHIDE, Hiroko

TAGO, Masao

ENDO, Keigo

KATO, Mamoru

NISHIKAWA, Keiichi

TAKAHASHI, Yasuyuki

FUJIWARA, Rikichi

KAWABE, Atsushi

NIWA, Ohtsura

TAKASE, Tadashi

FUKUSHIMA, Yasuhiro

KIKUCHI, Kei

OGAWA, Kiyoshi

TAKEI, Yasutaka

HANAI, Kozo

KIKUCHI, Toru

OHNO, Kazuko

TANAMI, Yutaka

HARADA, Yasuo

KIMURA, Satoru

OKAMOTO, Takahide

TASHIRO, Satoshi

HOKKEDO, Manabu

KISHIMOTO, Kenjj

OKUDA, Yasuo

WAGATSUMA, Kei

HOSONO, Makoto

KITAMURA, Yoshiaki

OKUMURA, Yasuhiko

WATANABE, Hiroshi

ICHIDA, Takao

KOYAMA, Shuji

ONO, Kinya

YANAGIDA, Sachiko

IDA, Masahiro

KUBOTA, Kazunori

ONO, Koji

YANAGIDA, Yuji

IDA, Yoshihiro

KUDOH, Yasuyuki

SAI, Masahiro

YAMAGUCHI, Ichiro

IGARASHI, Takayuki

KUNUGITA, Naoki

SAITO, Kyoko

YAMASHITA, Shunichi

IKEBUCHI, Shuji

MACHITORI, Akihiro

SASAKAWA, Yasuhiro

YONAI, Shunsuke

IMABAYASHI, Etsuko,

MAGATA, Yasuhiro

SASAKI, Takeshi

YONEKURA, Yoshiharu

INUBUSHI, Masayuki

MAKI, Hiroaki

SASAKI, Yasuhito

YOSHIDA, Kazunori

MATSUO, Ayae

SAKAMOTO, Hajime

The Japan Central Organization on Quality Assurance of Breast Cancer Screening

International advisors
Dr LAU, Lawrence, International Radiology Quality Network (IRQN) and International
Society of Radiology (ISR), Australia
Dr PEREZ, Maria del Rosario, World Health Organization (WHO), Switzerland
Dr REHANI, Madan, International Organization for Medical Physics (IOMP), International
Commission on Radiological Protection (ICRP), Harvard Medical School and
Massachusetts General Hospital, Boston
Dr SHANNOUN, Ferid, UN Scientific Committee on the Effects of Atomic Radiation(UNSCEAR), Austria

Contents
1. Background of Establishment of Diagnostic Reference Levels …………………………….1

2. Purpose of Establishing Diagnostic Reference Levels……………………………………….2
2.1 Features of Diagnostic Reference Levels
2.2 Approaches for Use of Diagnostic Reference Levels in Medical Settings

3. National Diagnostic Reference Levels Established in 2015 (Japan DRLs 2015)……………5
3.1

Japan DRLs 2015 for Computed Tomography

3.1.1 Japan DRLs 2015 for Adult Computed Tomography
3.1.2 Japan DRLs 2015 for Paediatric Computed Tomography
3.2

Japan DRLs 2015 for General Radiography

3.3

Japan DRL 2015 for Mammography

3.4

Japan DRLs 2015 for Dental Intraoral Radiography

3.5Japan DRL 2015 for Fluoroscopically Guided Interventional Procedures

3.6

Japan DRLs 2015 for Nuclear Medicine

1. Background of Establishment of Diagnostic Reference Levels
International guidelines, such as the recommendations and guidance published by theInternational Commission on Radiological Protection (ICRP) and International Basic Safety
Standards published by the International Atomic Energy Agency (IAEA), state that diagnostic
reference levels (DRLs) are important tools for optimisation of image quality and the radiationdose delivered to patients in diagnostic fields. The approach to establish DRLs includes not only
setting radiation dose levels but also determining dose quantities and units used to set DRLs,
standardising methodology for dose measurements, collecting data and determining the application
methods of DRLs. These processes are closely related to quality control of equipment and protocol.
Thus, DRLs are important in the optimisation process.
Overseas, the European Union (EU) issued the Council Directive 97/43/Euratom (June 1997),
which required all member states to establish DRLs for controlling diagnostic radiation, and DRLs
have subsequently been introduced in each country of EU. In the United States, DRLs presented byorganisations such as the American College of Radiology (ACR), American Association of
Physicists in Medicine (AAPM) and National Council on Radiation Protection and Measurements(NCRP) have been adopted as actual standards.
In Japan, various societies, researchers and organisations, including the J-RIME liaisonorganisations, have performed the radiation dose surveys associated with imaging examinations
and have independently proposed values as reference dose levels. However, these activities havenot been performed with sufficient cooperation among all organisations concerned with thescientific and related aspects of medical radiation protection; thus, no ‘Japan DRLs’ have been
widely recognised or actually implemented in medical care settings in Japan.
In March 2010, the J-RIME was established to enable related organisations to coordinate andshare research information related to medical exposure. Among the activities of the J-RIME, a
DRL working group (DRL-WG), comprising members recommended by each the J-RIME liaisonorganisation, was established in August 2014 to first establish Japan DRLs. Following acollaboration of liaison organisations on a single platform and detailed discussions on dosequantities and units used to set DRLs and survey design, some liaison organisations performed
large-scale nationwide surveys. Committee members of DRL-WG discussed all survey data
available from liaison organisations in consideration of comments from experts within and outsideof Japan. All activities for establishing DRLs were performed with transparency and objectivity;
this was required for accepting the proposed Japan DRLs 2015 as reasonable standards andsupporting their wide use throughout Japan.

12. Purpose of Establishing Diagnostic Reference Levels
2.1 Features of Diagnostic Reference Levels
ICRP defines DRLs as ‘a form of investigation level, applied to an easily measured
quantity, usually the absorbed dose in air or tissue-equivalent material at the surface of asimple standard phantom or a representative patient’.1 This definition strongly emphasisesthat DRLs are not dose limits and do not help distinguish between good and poor medical
practice.2 Although dose limits must not be exceeded, DRLs may be exceeded if clinicallynecessary.1 DRLs also differ from dose limits for occupational exposure because they are notused to constrain individual patient exposures; this is because a dose higher than the standard
dose may be required depending on the patient’s body size and weight. DRLs are a tool for
identifying facilities with unusually high doses and for promoting the optimisation process.
Separate DRLs have been established for each country and/or region because equipment andprocedure protocols can vary between different facilities in countries or regions. DRLs are set
for patients with standard sizes or for standard phantoms in easily measurable and highly
reproducible dose metrics; they should not be set as effective doses.2 Image quality is
considered when setting DRLs.
When setting DRLs, dose measurements are first performed using a previously
standardised method for each type of radiation examination. DRLs are generally set as the75th percentile of the typical dose distribution for a patient or phantom measurement.
However, this does not necessarily apply to examinations with narrower dose distributions
because of the effect of optimisation.
DRLs that have been established in certain countries or regions are also periodicallyreviewed in accordance with changes in clinical practice and equipment. The Japan DRLs
2015 also should be reviewed at certain time intervals in response to changes in the state ofradiation-based medical care and to advances in devices or methods. Accordingly, periodicalcollection of data regarding diagnostic radiology doses throughout Japan will be needed, andtechnological progress for these dose surveys are being promoted. Currently, the use of
DICOM (PS3.16)-standardised Radiation Dose Structured Reports for electronicallygathering information related to medical exposure is being investigated using radiation
diagnostic equipment.4-7
In addition to DRLs, achievable dose (AD) and diagnostic reference range (DRR) are also
tools for optimisation of patient protection. ADs are set at approximately 50th percentile of thedose distribution. DRLs will provide incentives for optimisation for the 25% of facilities thatuse dose over the DRLs for a particular examination. Then, NCRP recommends the use of ADs
to encourage optimisation for the 75% of facilities that already use dose within the current
DRLs.3 The use of DRRs has also been proposed as a useful approach for quality improvement.
DRR can indicate investigation or action levels ranging from the lower value, below which
reduced image quality may not be diagnostic, to the upper values, above which the dose may bein excess.8

2

2.2 Approaches for Use of Diagnostic Reference Levels in Medical Settings
When the typical dose used at a facility exceeds DRLs without clinical needs, a review
should be performed to determine whether the dose has been optimised. In general, theequipment performance and protocols (procedures) are investigated, the reason for higher doses
is found and optimisation actions are implemented. After implementing such measures, thetypical dose at the facility is again evaluated to ensure that it is below DRL. NCRP recommends
that protocols and practice be periodically reviewed (e.g. at least annually) to ensure that the
protocols and techniques have not inadvertently changed periodically.3 Protocols for new
equipment should be initially assessed before the equipment is used for patient examinations
and reassessed after a longer (i.e. at 3–6 months) experience has been obtained.3 During allthese steps, the need for adequate image quality, but not the highest image quality, should beconsidered.
The purpose of DRLs is not dose reduction but optimisation. If a justified examination does
not provide the necessary clinical information because of too low dose resulting in an
inadequate image quality, then the patient has been exposed needlessly to radiation. In practice,
it is assumed that the necessary dosage, including to the margins, will be used.
In medical settings, it is necessary to first compare an institution’s doses with DRLs in the
optimisation process. However, in medical settings where a dosimeter is not available, thedose comparison may be difficult. A possible countermeasure for this problem is the use ofvalues calculated using Non Dosimeter Dosimetry9 or conventional software for calculatingradiation exposure dose or values displayed on equipment as a substitute. In addition, systems
should be constructed in which dosimeters or phantoms owned by the affiliated organisation orother facility can be used.
DRLs may also be used for international comparisons.10 DRLs based on standard phantoms
can be compared with those of other countries. However, when considering DRLs based on‘standard’ patients, caution is necessary, because the sizes of Western and Japanese patientsclearly differ.

References
1) International Commission on Radiological Protection, 1996. Radiological protection andsafety in medicine. ICRP Publication 73. Ann. ICRP 26 (2)2) Vassileva J, Rehani M, 2015. Diagnostic reference levels, American Journal of
Roentgenology 204, W1-W3.
3) National Council on Radiation Protection and Measurements, 2012. NCRP report 172.
Reference Levels and Achievable Doses in Medical and Dental Imaging: Recommendations
for the United States.
4) The Association of Electrical Equipment and Medical Imaging Manufacturers, 2015.
DICOM Standard, http://medical.nema.org/standard.htm.
5) International Electrotechnical Commission, IEC 61910-1 ed.1.0, 2014. Medical electrical3

equipment - Radiation dose documentation - Part 1: Radiation dose structured reports forradiography and radioscopy.
6) International Electrotechnical Commission, IEC 60601-2-44 ed.3.0, 2009. Medical electricalequipment - Part 2-44: Particular requirements for the basic safety and essential
performance of X-ray equipment for computed tomography.
7) International Electrotechnical Commission, IEC 60601-2-43 ed.2.0, 2010. Medical electricalequipment - Part 2-43: Particular requirements for the basic safety and essential
performance of X-ray equipment for interventional procedures.
8) Goske M, Strauss K, Coombs L, et al., 2013. Diagnostic reference ranges for pediatricabdominal CT. Radiology 268, 208-218.
9) Mori T, Suzuki M, et al., 1997. A Study of creating guidance level in medical exposure,
Research Reports of Suzuka University of Medical Science and Technology, 4, 109-129. (inJapanese)10) Australian Radiation Protection and Nuclear Safety Agency, last revision 2013. National
Diagnostic Reference Level Fact Sheet
http://www.arpansa.gov.au/services/ndrl/ndrlFactsheet.cfm (accessed 17 March 2015).

4

3. National Diagnostic Reference Levels Established in 2015 (Japan
DRLs 2015)
The following are recommended as national DRLs in Japan.
3.1

Japan DRLs 2015 for Computed Tomography

3.1.1 Japan DRLs 2015 for Adult Computed Tomography
CTDIvol (mGy)

DLP (mGy·cm)

Routine brain

85

1350

Routine chest

15

550

Chest to pelvis

18

1300

Abdomen to pelvis CT

20

1000

Liver, multi-phase

15

1800

Coronary CTA
9014001) Standard patient weight: 50–60 kg or 50–70 kg for coronary CTA.
2) Liver, multiphase does not include the chest region or pelvis.

3.1.2 Japan DRLs 2015 for Paediatric Computed Tomography
Younger than 1 year

1–5 years

6–10 years

CTDIvol(mGy)

DLP
CTDIvol(mGy·cm) (mGy)

DLP
CTDIvol(mGy·cm) (mGy)

DLP(mGy·cm)

Head CT

38

500

47

660

60

850

Chest CT

11 (5.5)210 (105)

14 (7)

300 (150)

15 (7.5)410 (205)

Abdomen CT
11 (5.5)220 (110) 16 (8)400 (200) 17 (8.5)
530 (265)
1) Values for a 16-cm diameter phantom along with values for a 32-cm diameter phantom inparentheses.

53.2 Japan DRLs 2015 for General Radiography
Examinations

Entrance surface
Examinations
dose (mGy)

Entrance surface
dose (mGy)

Skull

3.0

Pelvis3.0

Lateral of the skull

2.0

Femur

2.0

Cervical spine

0.9

Ankle joint

0.2

Thoracic spine

3.0

Forearm

0.2

Lateral of the thoracic spine

6.0

Guthmanna)

6.0

b)

Chest P→A

0.3

Martius

Abdomen

3.0

Infant chest

0.2

Lumbar spine

4.0Child chest

0.2

Lateral of the lumbar spine
11.0
Infant hip jointa) Lateral pelviography for pregnant womenb) Superior–interior pelviography for pregnant women

6

7.0

0.2

3.3 Japan DRL 2015 for Mammography
 Mean glandular dose: 2.4 mGy (95th percentiles)

73.4 Japan DRLs 2015 for Dental Intraoral Radiography*Standard intraoral radiography using the bisecting or paralleling technique was subject tothis survey. Bitewing radiography, occlusal radiography (bisecting technique and axial
projection technique) and others were not included.
Examination site

PED (mGy)a)
Adultb)Childc)MaxillaIncisor
1.3
0.9
Canine1.6
1.0
Premolar
1.7
1.1
Molar
2.3
1.3
Mandible
Incisor
1.1
0.7
Canine1.1
0.9
Premolar
1.2
0.9
Molar
1.8
1.1
a) Patient entrance dose (PED) is the air kerma in cone-tip free air not including the patient’s
backscattering.
b) Adult patient with standard sizec) Ten-year-old paediatric patient8

3.5 Japan DRL 2015 for Fluoroscopically Guided Interventional Procedures
 Fluoroscopic radiation dose rate: 20 mGy/min (interventional reference point dose rate)

93.6 Japan DRLs 2015 for Nuclear Medicine
Diagnostic Nuclear Medicine

DRLs (MBq)a)

Bone: 99mTc-MDP

950

99m

950

Bone:

Tc-HMDP

Bone marrow:

111

In-Cl

120

Cerebral blood flow:

99m

800

Cerebral blood flow:

99m

1200

Cerebral blood flow: 99mTc-ECD (rest or stress)

800

99m

1100

Cerebral blood flow: 123I-IMP (rest or stress)

200

123

I-IMP (rest and stress)

300

123

Cerebral blood flow: Iomazenil ( I)

200

123

190

Tc-HM-PAO (rest or stress)
Tc-HM-PAO (rest and stress)

Cerebral blood flow:

Tc-ECD (rest and stress)

Cerebral blood flow:

Dopamine transporter: Ioflupane ( I)111

Cisternography:

In-DTPA70

Thyroid imaging:

123

10

Thyroid imaging:

99m

300

Parathyroid : 201Tl-Cl

120

Parathyroid :99m

Parathyroid :

99m

I-NaI
Tc-pertechnetate

Tc-pertechnetate300

Tc-MIBI

800

Lung ventilation:

81m

Kr-gas200

Lung ventilation:

133

Xe-gas

48099m

Tc-MAA

260

99m

Tc-MAA

500

Liver and spleen: 99mTc-phytate

200

Lung perfusion:
Venography:

Liver function:

99m

Tc-GSA260

Hepatobiliary: 99mTc-PMT

260

Liver and spleen:

99m

Tc-Sn colloid

Myocardial perfusion:
Myocardial perfusion

201

180

Tl-Cl

180

Tc-tetrofosmin (rest or stress)

900

99m

Myocardial perfusion:

99m

1200

Myocardial perfusion:

99m

900

Myocardial perfusion:

99m

1200

Tc-tetrofosmin (rest and stress)
Tc-MIBI (rest or stress)
Tc-MIBI (rest and stress)

Myocardial fatty acid metabolism: 123I-BMIPP
Cardiac sympathetic nerve imaging:

123

I-MIBG

130
130

Cardiac blood pool:

99m

1000

Cardiac blood pool:

99m

1000

Tc-HSA
Tc-HSA-D

10

Myocardial infarction: 99mTc-PYP

800

99m

370

Salivary gland:

Tc-pertechnetate

Meckel's diverticulum:99m

Tc-pertechnetate

500

Gastrointestinal bleeding: 99mTc-HSA-D
Renal imaging (static):

1040

99m

Tc-DMSA

210

Renal imaging (dynamic):

99m

400

Renal imaging (dynamic):

99m

400

Adrenal cortex:

131

Adrenal medulla:

Tc-DTPA

I-Adosterol

44

131

I-MIBG

45

I-MIBG

130

123

Adrenal medulla

Tc-MAG3

Tumour: 201Tl-Cl

180
67

Tumour and inflammation: Ga-citrate

200

Lymphatic system: 99mTc-HSA-D (not covered with health insurance)

950

Sentinel lymph node:

99m

120

Sentinel lymph node:

99m

120

Tc-Sn colloid
Tc-phytate

99 m

1000

18

Tumour: F-FDG (in-house-produced)

240

18

240

RI angiography:

Tc-HSA-D

Tumour : F-FDG (delivery)
18

Brain : F-FDG (in-house-produced)

240

Brain: 18F-FDG (delivery)

240

15

8000

15

6000

15

3000

15

2900

15

7000

15

7500

O-CO2 gas: 2D
O-O2 gas: 2D
O-CO gas: 2D
O-CO2 gas: 3D
O-O2 gas: 3D
O-CO gas: 3D

Myocardiac metabolism: 18F-FDG (in-house-produced)
18

Myocardiac metabolism: F-FDG (delivery)
Myocardiac perfusion: 13N-NH3a) Adult dosage (MBq)

240
240
720

11