ORAU Team

Dose Reconstruction Project for NIOSH

Technical Basis Document for the Mound Site – Occupational 

Medical Dose

Document Number:

ORAUT-TKBS-0016-3 

Effective Date: 07/08/2005 

Revision No.: 01 PC-1 

Controlled Copy No.: ______

Page 1 of 17

Subject Experts: Faisal Algutifan, Vernon E. Shockley and 

Ronald L. Kathren

Document Owner

Approval: Signature on File Date: 09/03/2004

Jeffrey S. Vollmer, TBD Team Leader

Approval: Signature on File Date: 08/30/2004

Judson L. Kenoyer, Task 3 Manager

Concurrence: Signature on File Date: 08/30/2004

Richard E. Toohey, Project Director

Approval: Signature on File Date: 09/09/2004

James W. Neton, Associate Director for Science

Supersedes:

Revision No.: 00

TABLE OF CONTENTS

Section

Record of Issue/Revisions ...................................................................................................................

Page

3

Acronyms and Abbreviations ...............................................................................................................4

3.1 Introduction ..............................................................................................................................5

3.2 Examination Frequency, Equipment, and Techniques.............................................................. 5

3.3 Organ Dose Calculations .........................................................................................................6

3.4 Uncertainty Analysis...............................................................................................................11

3.5 Instruction Guide for Dose Reconstructors............................................................................. 13

References ........................................................................................................................................14

GLOSSARY.......................................................................................................................................15
Effective Date: 09/09/2004 Revision No. 01 Document No. ORAUT-TKBS-0016-3 Page 2 of 17

LIST OF TABLES

Table

3-1 Frequency of required occupational PA chest X-rays ...............................................................

Page

5

3-2 Technique factors used for PA chest X-rays............................................................................. 6

3-3 Technique factors used for lateral chest X-rays........................................................................ 6

3-4 Organ dose estimates for PA chest radiographs before 1970 assuming 

minimal collimation...................................................................................................................7

3-5 Organ dose estimates for PA chest radiographs from 1970 - 1979 .......................................... 7

3-6 Organ dose estimates for PA chest radiographs from 1980 to 1987......................................... 8

3-7 Organ dose estimates for PA chest radiographs from 1988 to 1994......................................... 8

3-8 Organ dose estimates for PA chest radiographs from 1995 to 1996......................................... 9

3-9 Organ dose estimates for PA chest radiographs from 1997 to 1999......................................... 9

3-10 Organ dose estimates for PA chest radiographs from 2000 to 2003....................................... 10

3-11 Organ dose estimates for LAT chest radiographs from 1988 to 2003..................................... 10
Effective Date: 07/08/2005 Revision No. 01 PC-1 Document No. ORAUT-TKBS-0016-3 Page 3 of 17

RECORD OF ISSUE/REVISIONS

ISSUE 

AUTHORIZATION 

DATE

EFFECTIVE 

DATE REV. NO. DESCRIPTION

Draft 03/18/2004 00-A New technical basis document for the Mound 

Site – Occupational Medical Dose. Initiated by 

Jeffrey S. Vollmer.

Draft 05/18/2004 00-B Incorporates NIOSH review comments. 

Initiated by Jeffrey S. Vollmer.

Draft 05/19/2004 00-C Incorporates NIOSH final review comment. 

Initiated by Jeffrey S. Vollmer.

05/28/2004 05/28/2004 00 First approved issue. Initiated by Jeffrey S. 

Vollmer.

Draft 08/26/2004 01-A Incorporates Office of General Counsel 

comments. Initiated by Jeffrey S. Vollmer.

09/09/2004 09/09/2004 01 Approved Issue of Revision 01. Initiated by 

Jeffrey S. Vollmer.

09/09/2004 06/17/2005 01 PC-1-A Page change to correct organ dose estimates 

in Table 3-4 on page 7, in Section 3. Initiated 

by Elyse M. Thomas.

09/09/2004 07/08/2005 01 PC-1 Approved page change revision. No changes 

were needed as a result of NIOSH formal 

review. No retraining is required. Initiated by 

Elyse M. Thomas.

Approval:

Document Owner:

Jeffrey S. Vollmer, TBD Team Leader

Signature on File______________07/05/2005

Judson Kenoyer, Task 3, Manager

Signature on File_____________ 07/05/2005 

Richard E. Toohey, Project Director

Signature on File______________06/29/2005

James W. Neton, Associate Director for Science

Signature on File______________07/08/2005
Effective Date: 09/09/2004 Revision No. 01 Document No. ORAUT-TKBS-0016-3 Page 4 of 17

ACRONYMS AND ABBREVIATIONS

cGy centigray

cm centimeter

ESE entrance skin exposure

Gy Gray

HVL half-value layer

ICRP International Commission on Radiological Protection

kVp peak kilovoltage

LAT lateral

Lucal Lucite aluminum

mA milliampere

mAs milliampere-second

mGy milligray

mm millimeter

mR milliroentgen

NCRP National Council on Radiation Protection and Measurements

NIOSH National Institute for Occupational Safety and Health

PA posterior–anterior

R roentgen

s second

SID source-to-image distance

SSD source-to-skin distance

U.S.C. United States Code

VCH vertical cassette holder
Effective Date: 09/09/2004 Revision No. 01 Document No. ORAUT-TKBS-0016-3 Page 5 of 17

3.1 INTRODUCTION

Technical Basis Documents and Site Profile Documents are general working documents that provide 

guidance concerning the preparation of dose reconstructions at particular sites or categories of sites. 

They will be revised in the event additional relevant information is obtained about the affected site(s). 

These documents may be used to assist the National Institute for Occupational Safety and Health 

(NIOSH) in the completion of the individual work required for each dose reconstruction.

In this document the word “facility” is used as a general term for an area, building, or group of 

buildings that served a specific purpose at a site. It does not necessarily connote an “atomic weapons 

employer facility” or a “Department of Energy facility” as defined in the Energy Employee 

Occupational Illness Compensation Program Act of 2000 [42 U.S.C. Sections 7384l(5) and (12)]. 

Diagnostic X-ray procedures were a contributor to the occupational radiation exposure of Mound 

workers. In general, the dose from such exposures was not measured, considered, or included as 

part of the overall occupational exposure of the employee, although it clearly was occupationally 

related. Diagnostic medical X-rays administered in conjunction with routine or special physical 

examinations required for employment are a valid source of occupational exposure. Unlike 

occupational exposures incurred during normal work processes, individual diagnostic medical X-ray 

exposures were not monitored, necessitating reconstruction of doses acquired in this manner. This 

section describes the technical aspects of dose reconstruction from medical X-rays administered prior 

to employment and periodically thereafter as a condition of employment. This discussion is based on 

ORAU (2003).

3.2 EXAMINATION FREQUENCY, EQUIPMENT, AND TECHNIQUES

Employees at the Mound site received posterior–anterior (PA) chest X-rays as follows: A baseline at 

hiring, at specified intervals thereafter (Table 3-1), and at termination. In 1983, a policy modification 

required X-rays for terminating employees only if they had not had a chest X-ray within the previous 9 

months (Mound 2002); this changed to a 6 months in 1988. In 1988, a lateral (LAT) view was 

required for women known to have undergone breast augmentations; the frequency of these 

examinations is not known (Mound 2002). Table 3-1 lists examination frequencies over the years for 

different groups based on information obtained from the Mound data files. 

Table 3-1. Frequency of required occupational PA chest X-rays. 

Period Frequency Comment

1946 To 1959 Annually All employees 

1960 To 1979 Annually Certain employees according to job category

Biennially Based on job category

1980 To 1988 Every 6 years Employees under age 35

Every 4 years Employees between age 35 to 44 

Every 2 years Employees age 45 and older

Annually Asbestos workers

Annually Any employee considered at risk in workplace (e.g., welders, etc).

1989 To 2003 Every 5 years Employees under age 35 

Every 4 years Employees between age 35 and 44

Every 2 years Employees age 45 and older

Annually Smoker, any age

Since at least 1980, the X-ray apparatus at Mound was a stationary enclosed unit with the control 

panel separated from the tube head by a wall. For the period before 1980, details about the X-ray 

apparatus and technique parameters are not known, and default values from ORAU (2003) were used 

for entrance kerma. From 1980 through 2003, the equipment consisted of a single-phase, TWX-325 
Effective Date: 09/09/2004 Revision No. 01 Document No. ORAUT-TKBS-0016-3 Page 6 of 17

control unit with a Eureka Emerald 125 X-ray tube, Eureka Linear II automatic collimator, and S&S 

1417B vertical cassette holder (VCH) used with no grid and 14- by 17-in. Kodak X-O-Matic Regular 

film. Actual measurement data obtained by the Ohio Department of Health were used. Tables 3-2 

and 3-3 summarize technique parameters and entrance kerma for PA and LAT views, respectively. 

For the period before 1980, no external collimation was assumed when converting entrance kerma to 

organ doses. 

Table 3-2. Technique factors used for PA chest X-rays. 

Period

Total filtration

(mm Al)

Half-value 

layer (mm Al)

Current

(mA)

Voltage

(kVp)

Exposure 

time (s)

Entrance 

kerma (mGy)

Pre-1970 Unknown Unknown Unknown Unknown Unknown 2.0a

1970-1979 Unknown Unknown Unknown Unknown Unknown 1.0a

1980-1987 3.0 2.5 Unknown Unknown Unknown 0.5a

1988-1994 3.3 3.0 200 84 1/20 0.5a

1995-1996 3.3 3.0 200 84 1/20 0.164

1997-1999 3.3 3.0 200 84 1/20 0.159

2000-2003 3.3 3.0 200 82 1/20 0.149

a. Default values from ORAU (2003). 

Table 3-3. Technique factors used for lateral chest X-rays. 

Period

Total filtration 

(mm Al)

Half-value 

layer

Current

(mA)

Voltage

(kVp)

Exposure 

time(s)

Entrance kerma 

(mGy)

9/1988 to 2003 3.3 4.0 200 110 1/20 0.40a

a. Entrance kerma 2.5 times the PA entrance kerma for same period. 2.5 × 0.159 mGy = 0.4 mGy.

Although there is no specific evidence in the history data file (Mound 2002) to indicate the use of 

photofluorography at Mound, evidence suggests that General Electric mobile X-ray units might have 

been used at various U.S. Atomic Energy Commission, Energy Research and Development 

Administrations, or U.S. Department of Energy sites (NCRP 1989). A review of files from the 1940s 

and 1950s reveals that when photofluorography was used, an unusually large number of X-ray 

examinations would be performed in a given day. Thus, a larger than normal number of X-ray records 

for a given day might be a positive indicator of the use of photofluorography. However, in the 

absence of specific data on the use of photofluorography at Mound, or even that such equipment was 

present on site, this analysis assumes that photofluorography did not occur at Mound. 

3.3 ORGAN DOSE CALCULATIONS

Organ doses are calculated by multiplying the entrance kerma listed in Table 3-2 by the appropriate 

organ dose conversion factor obtained from Tables A.2 to A.8 in International Commission on 

Radiological Protection (ICRP) Publication 34 (ICRP 1982). The specific organ doses are shown in 

Tables 3-4 through 3-10 for PA X-ray procedures and Table 3-11 for LAT procedures. As noted 

above, the conservative default values from ORAU (2003) were used for the period before 1988 for 

entrance kerma [entrance skin exposure (ESE)]. For the period from 1988 to 2003, data obtained by 

measurement by the State of Ohio were used. 

The Ohio Department of Health made measurements during radiation safety and compliance surveys 

in 1995, 1997, and 2000. The analysis determined ESE values using a Lucite-aluminum (Lucal) chest 

phantom, representing a 23-cm-thick chest at a 183-cm source-to-image distance (SID). The values 

for 1995, 1997, and 2000 are 16.4 mR, 15.9 mR, and 14.9 mR, respectively. The 1995 measured 

value was used for 1995 and 1996; the 1997 value is used for 1997 to 1999, and the 2000 value was 

used for 2000 to 2003. Entrance kerma and doses are assumed to be numerically equal to the ESE 

(that is, 1 cGy is equal to 1 R is equal to 1 rem, which are claimant-favorable assumptions). 
Effective Date: 07/08/2005 Revision No. 01 PC-1 Document No. ORAUT-TKBS-0016-3 Page 7 of 17

Table 3-4. Organ dose estimates for PA chest radiographs before 

1970 assuming minimal collimation. 

Organ

Dose conversion factor 

(mGy/Gy air kerma) (beam 

quality for 2.5 mm Al HVL)a

Organ dose 

(rem)

Thyroid 174 3.48E-02

Eye/brain 32 6.40E-03

Ovaries 168 3.36E-02

Urinary/bladder 168 3.36E-02

Colon/rectum 168 3.36E-02

Testes 9.1 1.82E-03

Lungs 451 9.02E-02

Thymus 451 9.02E-02

Esophagus 451 9.02E-02

Stomach 451 9.02E-02

Bone surface 451 9.02E-02

Liver/gall bladder/spleen 451 9.02E-02

Remainder 451 9.02E-02

Breast 49 9.80E-03

Uterus(embryo) 149 2.98E-02

Bone marrow 92 1.84E-02

Skinb 2.70E-01

a. Dose conversion factors from ORAU (2003), p. 18, p.21, and ICRP 34 (1982, 

Tables A.2 to-A.8). 

b. Skin dose was determined by multiplying ESE by backscatter factors of 1.35., 

1.39, and 1.4 for half-value layers (HVLs) of 2.5, 3.0, and 4.0 mm, Al 

respectively. From NCRP (1989, Table B-8). 

Table 3-5. Organ dose estimates for PA chest radiographs from 

1970 to 1979. 

Organ

Dose conversion factor 

(mGy/Gy air kerma) 

(beam quality for 2.5 mm 

Al HVL)a

Organ dose 

(rem)

Thyroid 32 3.20E-03

Eye/brain 32 3.20E-03

Ovaries 1 1.00E-04

Urinary/bladder 1 1.00E-04

Colon/rectum 1 1.00E-04

Testes 0.01 1.00E-06

Lungs 451 4.51E-02

Thymus 451 4.51E-02

Esophagus 451 4.51E-02

Stomach 451 4.51E-02

Bone surface 451 4.51E-02

Liver/gall bladder/spleen 451 4.51E-02

Remainder 451 4.51E-02

Breast 49 4.90E-03

Uterus(embryo) 1.3 1.30E-04

Bone marrow 92 9.20E-03

Skinb 1.35E-01

a. Dose conversion factors from ICRP (1982, Tables A.2 to A.8).
Effective Date: 09/09/2004 Revision No. 01 Document No. ORAUT-TKBS-0016-3 Page 8 of 17

b. Skin dose was determined by multiplying ESE by backscatter factor of 1.35 

from NCRP (1989, Table B-8). 

Table 3-6. Organ dose estimates for PA chest radiographs from 1980 

to 1987. 

Organ

Dose conversion factor 

(mGy/Gy air kerma) (beam 

quality for 2.5 mm Al HVL)a Organ dose (rem)

Thyroid 32 1.60E-03

Eye/brain 32 1.60E-03

Ovaries 1 5.00E-05

Urinary/bladder 1 5.00E-05

Colon/rectum 1 5.00E-05

Testes 0.01 5.00E-07

Lungs 451 2.26E-02

Thymus 451 2.26E-02

Esophagus 451 2.26E-02

Stomach 451 2.26E-02

Bone surface 451 2.26E-02

Liver/gall bladder/spleen 451 2.26E-02

Remainder 451 2.26E-02

Breast 49 2.45E-03

Uterus(embryo) 1.3 6.50E-05

Bone marrow 92 4.60E-03

Skinb 6.45E-02

a. Dose conversion factors from ICRP (1982) Tables A.2 through A.8.

b. Skin dose was determined by multiplying ESE by backscatter factor of 1.35. From 

NCRP Report No. 102 (1989, Table B-8). 

Table 3-7. Organ dose estimates for PA chest radiographs from 

1988 to 1994. 

Organ

Dose conversion factor 

(mGy/Gy air kerma) (beam 

quality for 3.0 mm Al HVL)a

Organ dose 

(rem)

Thyroid 46 1.60E-03

Eye/brain 46 1.60E-03

Ovaries 1.8 5.00E-05

Urinary/bladder 1.8 5.00E-05

Colon/rectum 1.8 5.00E-05

Testes 0.01 5.00E-07

Lungs 535 2.26E-02

Thymus 535 2.26E-02

Esophagus 535 2.26E-02

Stomach 535 2.26E-02

Bone surface 535 2.26E-02

Liver/gall bladder/spleen 535 2.26E-02

Remainder 535 2.26E-02

Breast 69 2.45E-03

Uterus(embryo) 2.3 6.50E-05

Bone marrow 117 4.60E-03

Skinb 6.95E-02

a. Dose conversion factors from ICRP (1982, Tables A.2 to A.8).

b. Skin dose was determined by multiplying ESE by backscatter factor of 1.39 from 

NCRP (1989, Table B-8). 
Effective Date: 09/09/2004 Revision No. 01 Document No. ORAUT-TKBS-0016-3 Page 9 of 17

Table 3-8. Organ dose estimates for PA chest radiographs from 

1995 to 1996. 

Organ

Dose conversion factor 

(mGy/Gy air kerma) (beam 

quality for 3.0 mm Al HVL)a

Organ dose 

(rem)

Thyroid 46 7.54E-04

Eye/brain 46 7.54E-04

Ovaries 1.8 2.95E-05

Urinary/bladder 1.8 2.95E-05

Colon/rectum 1.8 2.95E-05

Testes 0.01 1.64E-07

Lungs 535 8.77E-03

Thymus 535 8.77E-03

Esophagus 535 8.77E-03

Stomach 535 8.77E-03

Bone surface 535 8.77E-03

Liver/gall bladder/spleen 535 8.77E-03

Remainder 535 8.77E-03

Breast 69 1.13E-03

Uterus(embryo) 2.3 3.77E-05

Bone marrow 117 1.92E-03

Skinb 2.35E-02

a. Dose Conversion Factors from ICRP 34 (1982, Tables A.2 to A.8).

b. Skin dose was determined by multiplying ESE by backscatter factor of 1.39 

from NCRP (1989, Table B-8). 

Table 3-9. Organ dose estimates for PA chest radiographs from 

1997 to 1999. 

Organ

Dose conversion factor 

(mGy/Gy air kerma) (beam 

quality for 3.0 mm Al HVL)a

Organ dose 

(rem)

Thyroid 46 7.31E-04

Eye/brain 46 7.31E-04

Ovaries 1.8 2.86E-05

Urinary/bladder 1.8 2.86E-05

Colon/rectum 1.8 2.86E-05

Testes 0.01 1.59E-07

Lungs 535 8.51E-03

Thymus 535 8.51E-03

Esophagus 535 8.51E-03

Stomach 535 8.51E-03

Bone surface 535 8.51E-03

Liver/gall 

bladder/spleen

535 8.51E-03

Remainder 535 8.51E-03

Breast 69 1.10E-03

Uterus(embryo) 2.3 3.66E-05

Bone marrow 117 1.86E-03

Skinb 2.21E-02

a. Dose conversion factors from ICRP (1982, Tables A.2 to A.8).

b. Skin dose was determined by multiplying ESE by backscatter factor of 1.39 

from NCRP (1989, Table B-8). 
Effective Date: 09/09/2004 Revision No. 01 Document No. ORAUT-TKBS-0016-3 Page 10 of 17

Table 3-10. Organ dose estimates for PA chest radiographs from 

2000 to 2003. 

Organ

Dose conversion factor 

(mGy/Gy air kerma) (beam 

quality for 3.0 mm Al HVL)a

Organ dose 

(rem)

Thyroid 46 6.85E-04

Eye/brain 46 6.85E-04

Ovaries 1.8 2.68E-05

Urinary/bladder 1.8 2.68E-05

Colon/rectum 1.8 2.68E-05

Testes 0.01 1.49E-07

Lungs 535 7.97E-03

Thymus 535 7.97E-03

Esophagus 535 7.97E-03

Stomach 535 7.97E-03

Bone surface 535 7.97E-03

Liver/gall 

bladder/spleen

535 7.97E-03

Remainder 535 7.97E-03

Breast 69 1.03E-03

Uterus(embryo) 2.3 3.43E-05

Bone marrow 117 1.74E-03

Skinb 2.07E-02

a. Dose conversion factors from ICRP (1982, Tables A.2 to A.8).

b. Skin dose was determined by multiplying ESE by backscatter factor of 1.39 

from NCRP (1989, Table B-8). 

Table 3-11. Organ dose estimates for LAT chest radiographs from 

1988 to 2003. 

Organ

Dose conversion factor 

(mGy/Gy air kerma) (beam 

quality for 4.0 mm Al HVL)a Organ dose (rem)

Thyroid 164 6.56E-03

Eye/brain 164 6.56E-03

Ovaries 2.5 1.00E-04

Urinary/bladder 2.5 1.00E-04

Colon/rectum 2.5 1.00E-04

Testes 0.1 4.00E-06

Lungs 351 1.40E-02

Thymus 351 1.40E-02

Esophagus 351 1.40E-02

Stomach 351 1.40E-02

Bone surface 351 1.40E-02

Liver/gall bladder/spleen 351 1.40E-02

Remainder 351 1.40E-02

Breast 343 1.37E-02

Uterus(embryo) 2.1 8.40E-05

Bone marrow (male) 76 3.04E-03

Skin b 5.60E-02

a. Dose conversion factors from ICRP (1982, Tables A.2 to A.8).

b. Skin dose was determined by multiplying ESE by backscatter factor of 1.40 

from NCRP (1989, Table B-8). 
Effective Date: 09/09/2004 Revision No. 01 Document No. ORAUT-TKBS-0016-3 Page 11 of 17

The mean air kerma for a chest LAT view is calculated at a distance of 144 cm, which is the source to 

skin distance (SSD). The SSD is calculated using the following equation: 

SSD = SID - Chest thickness – VCHd

SSD = SID - CT - 5 = 183 - 34 - 5 = 144 cm

where

SID = 183 cm;

VCHd = 5.0 cm; the distance between the VCH and the worker

CT = 34 cm; lateral chest thickness for a typical worker

The average air kerma is obtained from Figure 10.1 of the Handbook of Health Physics and 

Radiological Health (Shleien, Slaback, and Birky 1998) for a single-phase unit at 3.3-mm Al total 

filtration at 100 cm from the source per 100 mAs using the corresponding lateral technique factors 

listed in Table 3-3. Use of a 3.3-mm Al total filtration is based on data provided by beam quality 

analyses performed by the Ohio Department of Health and Human Services (Mound 2002). The air 

kerma value was 0.082 cGy. The analysis applied a geometric correction using the inverse square 

distance law to calculate air kerma at 144 cm. The calculated geometric correction factor was 0.48. 

The mean air kerma for the LAT view was 0.04 cGy. All values are listed in Table 3-3. 

Organ doses were calculated by multiplying entrance kerma by the corresponding dose conversion 

factor. Tables 3-4 through 3-11 list organ doses.

3.4 UNCERTAINTY ANALYSIS

Error (deviation from the correct, true, or conventionally accepted value of a quantity) and uncertainty 

(defined in terms of the potential range of a stated, measured, assumed, or otherwise determined 

value of a quantity) provide an indication of the confidence of the dose estimates. Error implies 

knowledge of the correct or actual value, which in this case is, of course, not known. Therefore, the 

more appropriate factor is uncertainty, which is expressed in terms of a confidence level (e.g., a 99% 

confidence level indicates that the correct or true value, although not actually known, has a 99% 

probability of falling within the range cited). Uncertainty includes both precision and reproducibility of 

the measurement and accuracy, or how close the measurement or estimate of dose comes to the 

actual or correct value.

In theory, a large number of factors can introduce uncertainties or affect X-ray machine output 

intensity and dose to the worker. In practice, however, only five factors can reasonably have an 

impact on dose uncertainty: 

1. Measurement error

2. Variation in applied kilovoltage (kVp)

3. Variation in beam current (mA)

4. Variation in exposure time

5. Distance from the worker to the source of the X-rays [source-to-skin distance (SSD)]

The influence of such other factors as the use of screens, grids, reciprocity failure, film speed, and 

development, while potentially variable, would not affect the beam output intensity.

Medical X-ray doses, when measured, were derived largely from actual measurements of X-ray 

machine output with R-meters or similar ionization chamber devices designed for measurement of 

photons in the medical X-ray energy range. If properly calibrated and used, R-meters and similar 

instruments typically and historically have had an uncertainty of ±2% for photon energies below 400 
Effective Date: 09/09/2004 Revision No. 01 Document No. ORAUT-TKBS-0016-3 Page 12 of 17

keV (Kathren and Larson 1969). Although more recent versions of these instruments might provide a 

somewhat smaller uncertainly, perhaps on the order of ±1% (NBS 1985, 1988), for conservatism, 

dose reconstructors should apply the uncertainty range of ±2% to measurements of X-ray intensity.

Theoretically, for a given set of machine settings and parameters, X-ray output is constant and 

unvarying. In practice however, output is essentially constant unless focal spot loading occurs, as 

could be the case when the power rating of the machine is exceeded. It is unlikely that power ratings 

were ever exceeded because such an event would be difficult to achieve in practice and could result 

in damage to the X-ray tube. However, even with the use of constant voltage transformers to control 

line voltages, slight variations can occur in line voltage input or other internal voltages, which in turn 

can alter the kVp of the output beam. In general, for a given kVp setting, variation in kVp falls within 

+5% of the machine setting. Beam intensity is approximately proportional to the 1.7 power of the 

kilovoltage; this translates to an uncertainty of approximately ±8.6% with respect to output beam 

intensity in the 80 to 100 kVp used for diagnostic radiographs. For conservatism, this is rounded up to 

+9%.

Similarly, slight variations in tube current are normal; as a tube ages, or heats from use, current can 

change and typically drops. With all other factors constant, beam intensity is reduced in direct 

proportion to the change in tube current. Typically, the reduction in beam output from current 

variation is not more than a few percent under normal operating conditions; large decreases are 

readily detectable and result in maintenance on the machine to restore the output or, as a temporary 

measure, an increase in the current or kVp to provide the necessary intensity for proper radiography. 

There is no evidence to suggest that such temporary measures were ever used at Mound. For a 

given kVp setting, the output of the beam is a function of the tube current, which in turn is measured 

by an ammeter, which measures average tube current. The measurement is subject to uncertainties; 

there might be minor changes in output as the tube heats from normal use. Because these variations 

are typically small, the estimated uncertainty in beam output attributable to current variation is +5%. 

Another parameter that has potential to affect the dose from a diagnostic radiograph, perhaps 

significantly, relates to the time of exposure. A full-wave rectified machine produces 120 pulses per 

second of X-rays. In an exposure time of 1/20 of a second, only six pulses would result. A small error 

in the timer that resulted in a change of only +1 pulse would correspondingly affect the output by 

+17%. For an exposure time of 1/30 of a second, the change in output corresponding to a deviation 

of +1 pulse is +25%. Early mechanical timers were notoriously inaccurate; accuracy improved 

significantly with the introduction of electronic timers. Other than measurements of reproducibility 

made by the State of Ohio, there are no data on which to base an evaluation of the accuracy and 

precision of the timers on the Mound X-ray apparatus. The measurements made by the State 

suggest that the timers, and indeed the entire X-ray output from 1995 on, were reasonably constant. 

In addition, because the same apparatus was used since 1980, it is reasonable to conclude that timer 

errors since then were small. However, for conservatism, the assumed uncertainty in beam output 

attributable to timers is +25%. 

The final factor likely to affect worker dose is the SSD, which is a determinant of the ESE. For a given 

individual, the SSD will be determined largely by the body thickness of the worker and the accuracy of 

the positioning. For a typical worker, the estimated variation in SSD is no more than a few 

centimeters, with an upper limit of perhaps 7.5 cm. Using inverse square, this indicates an 

uncertainty of +10% from this source.

There are two approaches to determine the combined uncertainty from the five listed, potential 

sources of uncertainty. The first, and most conservative in that it gives the greatest range, is to 

assume that the uncertainties are additive, which yields an uncertainty range of 2 + 9 + 5 + 25 + 10 = 

+51%. However, a more reasonable approach would be to assume that the uncertainties are in fact 

random, and to compute the statistical root mean square value. That value is simply the square root 
Effective Date: 09/09/2004 Revision No. 01 Document No. ORAUT-TKBS-0016-3 Page 13 of 17

of the sum of the squares and computes as +28.9%. Rounding this up to +30% would seem to 

provide an adequate and suitably conservative indication of uncertainty. Thus, for an individual ESE 

or derived organ dose, dose reconstructions should assume an uncertainty of +30% at the 99% 

confidence level. To further ensure claimant favorability, reconstructions should assume that errors 

are all positive (that is, only +30% should be used). 

3.5 INSTRUCTION GUIDE FOR DOSE RECONSTRUCTORS 

Summarized below are instructions for dose reconstructors determining organ doses from required 

medical diagnostic X-ray procedures at Mound. In the absence of measurement data or other specific 

information, dose reconstructors can calculate organ doses for LAT view by multiplying the entrance 

kerma for the PA view by a default value of 2.5 and using this value along with the ICRP (1982) tables 

to compute the appropriate organ dose. Entrance kerma should be used to compute the organ doses 

associated with the LAT view; multiplying the organ doses obtained for the PA view by a factor of 2.5 

will result in erroneous results. For evaluation purposes, X-ray doses are always considered acute 

with photon energies in the range of 30 to 250 keV. Tables 3-4 to 3-11 list organ doses from PA and 

LAT chest radiography. The doses listed in the tables are per X-ray procedure. In absence of 

specific data, dose reconstructors should assume frequencies as listed in Table 3-1, but review of 

medical or other records could lead the dose reconstructor to determine that the actual frequency 

could have been greater or smaller. If so, the reconstructions should adjust annual doses 

accordingly.

For actual dose calculations, reconstructors should assume a normal distribution with an uncertainty

of +30% at the 99% confidence interval. However reconstructions should use only the positive 

uncertainty and multiply the doses listed in Tables 3-4 through 3-11 by a factor of 1.3 to include 

uncertainty at the 99% confidence interval. 
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REFERENCES

ICRP (International Commission on Radiological Protection), 1982, Protection of the Worker in 

Diagnostic Radiology, Publication 34, Pergamon Press, Oxford, England. 

Kathren, R. L., and H. V. Larson, 1969, “Radiological Calibration and Standardization for Health 

Physics: A Program, A Plea, and a Proposal,” Health Physics, volume 16, pp. 778-782.

Mound (Mound Laboratory), 2002, Mound X-Ray History, ORAU Cincinnati Operations Center 

Terminal Server, O:\DOE Site Images\Mound\Mound X-Ray History, downloaded September 

9, 2003 [Mound X-Ray History.PDF].

NCRP (National Council on Radiation Protection and Measurements), 1989, Medical X-Ray Electron 

Beam and Gamma-Ray Protection for Energies Up to 50 MeV (Equipment Design, 

Performance and Use), Report No. 102, Bethesda, Maryland. 

ORAU (Oak Ridge Associated Universities), 2003, Dose Reconstruction from Occupationally Related 

Diagnostic X-Ray Procedures, ORAUT-OTIB-0006, Revision 2, Oak Ridge, Tennessee.

NBS (National Bureau of Standards), 1985, Calibration and Related Services, NBS Special 

Publication 250, U.S. Department of Commerce, Gaithersburg, Maryland.

NBS (National Bureau of Standards), 1988, Calibration of X-ray and Gamma Ray Measuring 

Instrument. NBS Publication 250-16. U.S. Department of Commerce, Gaithersburg, Maryland. 

Shleien, B., L. A. Slaback, Jr., and B. K. Birky, 1998, Handbook of Health Physics and Radiological 

Health, Third Edition, Lippincott, Williams & Wilkins, Baltimore, Maryland.
Effective Date: 09/09/2004 Revision No. 01 Document No. ORAUT-TKBS-0016-3 Page 15 of 17

GLOSSARY

absorbed dose

The energy imparted per unit mass by ionizing radiation to matter at a specified point. The SI 

unit of absorbed dose is joule per kilogram (J/kg). The special name for this unit is gray (Gy). 

The previously used special unit of absorbed dose, rad, is being replaced by the gray. 1 rad = 

0.01 Gy. 1 Gy = 100 rad.

alternating electric current

Electric current that changes in magnitude and direction.

ampere

Electric current unit. One ampere is equal to one coulomb per second.

beam quality

The quality of an x-ray beam refers to its ability to penetrate matter.

centigray (cGy)

0.01 gray. 1 cGy equals one rad.

dose conversion factor

The ratio of dose equivalent in tissue or organ to entrance Kerma at the surface of the x-rayed 

person.

dose equivalent

The product of the absorbed dose in tissue, quality factor and all other necessary modifying 

factors at the location of interest. The SI unit for dose equivalent is the sievert. The historical 

unit for dose equivalent is the rem. The ICRP defines dose equivalent as equivalent dose.

entrance kerma

Refers to air kerma without backscatter.

exposure

A measure of the quantity of x or gamma radiation based upon its ability to ionize air through 

which it passes. The SI unit for exposure is coulomb per kilogram. The historical unit for 

exposure is Roentgen (R).

film

A medium used to record an image.

filtration

Material in the useful beam that usually absorbs preferentially the less penetrating radiation.

fluorography

The production of a photographic record of the image formed on the output phosphor of an 

image intensifier by the action of x-rays transmitted through the patient.

frequency

Number of cycles per second of alternating current.

gray (Gy)

The special name for SI unit of absorbed dose, Kerma, and specific energy imparted equal 

one joule per kilogram. One gray equals to one joule per kilogram. 
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electric current

The amount of charge per unit time passing a point in a conductor.

half-value layer (HVL)

Thickness of a specified substance which, when introduced in the path of a given beam of 

radiation, reduces the Kerma rate by one –half.

image

The pattern formed in the film due to beam interaction in the film composition after passage 

through the x-rayed person target of interest.

image quality

Refers to the visibility and sharpness of the images of structural details.

kerma

The sum of the initial kinetic energies of all charged ionizing particles liberated by uncharged 

ionizing particles per unit mass of a specified material. Kerma is measured in the same units 

as absorbed dose. The SI unit of kerma is joule per kilogram and its special name is gray 

(Gy). Kerma can be quoted for any specified material at a point in free space or in an 

absorbing medium.

milligray (mGy)

0.001 gray. 1 mGy = 10 rad.

phantom

An object used to simulate the absorption and scatter characteristics of the patient’s body for 

radiation measurement purposes.

radiography

The production of images on film by the action of x-rays transmitted through the patient.

rad

Historical unit for absorbed dose. One rad equals 100 ergs per gram. The word derives from 

radiation absorbed dose. 

roentgen (R)

The previously used special unit of exposure. An exposure of one roentgen will produce 2.58 

x10-4 coulomb of ions of either sign per kilogram in air.

rem

Historical unit of dose equivalent. The word derives from roentgen equivalent (in) man.

sievert (Sv)

The special name for the SI unit of dose equivalent. One Sievert equals one joule per 

kilogram. One sievert is equal to 100 rem.

source-to-image-distance (SID)

The distance measured along the central ray from the center of the front of the surface of the 

source (x-ray focal spot) to the surface of the image detector.

source to skin distance (SSD)

The distance measured along the central ray from the center of the front surface of the source 

(x-ray focal spot) to the surface of the irradiated object or patient.
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technique factors

Refer to x-ray machine settings used in an examination or procedure. The factors include 

such terms as kilovolt peak, milliampere, and exposure time. 

voltage

Electrical potential energy per unit charge. The SI unit is volt (V). One volt is equal to joule 

per coulomb.