ORAU Team

NIOSH Dose Reconstruction Project

Technical Basis Document for the Paducah Gaseous Diffusion 

Plant – Occupational Medical Dose

Document Number:

ORAUT-TKBS-0019-3 

Effective Date: 02/05/2004

Revision No.:00

Controlled Copy No.:______

Page 1 of 20

Subject Expert: James E. Turner

Document Owner

Approval: _Signature on File_____________Date: 02/09/2004 Jay J. Maisler, TBD Team Leader

Approval: Signature on File_____________ Date: 02/05/2004 Judson L. Kenoyer, Task 3 Manager

Concurrence: _Signature on File__________Date: 02/09/2004 Richard E. Toohey, Project Director

Approval: Signature on File______________Date: 02/11/2004 James W. Neton, OCAS Health Science Administrator

Supersedes:

None

TABLE OF CONTENTS

Section

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

Page

3

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

3.0 Occupational Medical Dose ........................................................................................................5

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

3.2 Examination Frequencies............................................................................................................5

3.3 Equipment And Techniques ........................................................................................................5

3.4 Organ Dose Calculations ............................................................................................................7

3.4.1 Air Kerma for Exposures from March 1975 to Present........................................................ 7

3.4.2 Air kerma for Exposures from 1952 through February 1975 ............................................... 8

3.4.3 Dose Equivalents per Exposure for Organs Included in ICRP Publication 34 ..................... 8

3.4.4 Dose Equivalents per Exposure for Organs not Included in ICRP Publication 34 ............... 9

3.4.5 Combined Dose Equivalents for PA and LAT Exposures.................................................. 10

3.5 Uncertainty................................................................................................................................11

3.6 Dose Reconstruction.................................................................................................................12

3.6.1 Claimant-Favorable Organ Dose Equivalents per Examination ........................................ 12

3.6.2 Optional Initial Screening.................................................................................................. 13

References ........................................................................................................................................15

Glossary ............................................................................................................................................16
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Attachment 3A Error Propagation for Kerma....................................................................................17

Attachment 3B Organ Dose Equivalents for Lumbar Spine Examinations........................................ 19

LIST OF TABLES

Table

3-1 Frequency of chest X-ray examinations.....................................................................................

Page

5

3-2 Description of X-ray equipment..................................................................................................6

3-3 Operating parameters................................................................................................................6

3-4 Average mAs for exposures of workers of different body size.................................................... 7

3-5 Air kerma at skin entrance for PA and LAT views ...................................................................... 8

3-6 Dose equivalent per PA and per LAT exposure for organs included in 

ICRP Publ. 34............................................................................................................................9

3-7 Dose equivalent per PA and per LAT exposure for organs not included in 

ICRP Publ. 34..........................................................................................................................10

3-8 Organ dose equivalents for combined PA and LAT examinations............................................ 11

3-9 Potential sources of uncertainty in organ dose-equivalent assessments.................................. 12

3-10 Claimant-favorable organ dose equivalents per examination consisting of 

one PA and one LAT exposure................................................................................................ 13

3-11 Upper-bound organ dose equivalents per examination for screening....................................... 13
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RECORD OF ISSUE/REVISIONS

ISSUE 

AUTHORIZATION 

DATE

EFFECTIVE 

DATE

REV. 

NO. DESCRIPTION

Draft 11/17/2003 00-A New technical basis document for the Paducah 

Gaseous Diffusion Plant – Occupational Medical 

Dose. Initiated by Jay J. Maisler.

Draft 12/09/2003 00-B Incorporates OCAS comments. Initiated by Jay J. 

Maisler. 

Draft 12/29/2003 00-C Incorporates revisions for consistency with 

ORAUT-TIB-0006 draft revision and responses to

additional internal comments. Initiated by Jay J. 

Maisler.

02/05/2004 02/05/2004 00 First approved issue. Initiated by Jay J. Maisler.
Effective Date: 02/05/2004 Revision No. 00 Document No. ORAUT-TKBS-0019-3 Page 4 of 20

ACRONYMS AND ABBREVIATIONS

Al aluminum

AP anterior-posterior (X-ray view)

cm centimeter

GE General Electric Corporation

Gy gray

HVL half-value layer

ICRP International Commission on Radiological Protection

IREP Interactive RadioEpidemiological Program

kerma Kinetic Energy Released per unit MA

kVp peak voltage (kilovolts)

ss (see Glossary)

LAT lateral (X-ray view)

mA milliampere

mAs milliampere second

mGy milligray

mm millimeter

mR milliroentgen

mrad millirad

mrem millirem

NCRP National Council on Radiation Protection and Measurements

NIOSH National Institute for Occupational Safety and Health

PA posterior-anterior (X-ray view)

PGDP Paducah Gaseous Diffusion Plant

QA quality assurance

SID source-to-image distance

SSD source-to-skin distance

TBD technical basis document
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3.0

3.1 INTRODUCTION

OCCUPATIONAL MEDICAL DOSE

The National Institute for Occupational Safety and Health (NIOSH) dose reconstruction project

requires assessment of doses from medical X-rays that were required as a condition of employment. 

The Paducah Gaseous Diffusion Plant (PGDP) occupational medicine program required 

preemployment and regular diagnostic chest X-ray examinations. The examinations consisted of one 

posterior-anterior (PA) and one lateral (LAT) chest projection. In addition to parts of the body 

exposed in the primary beam of an X-ray machine, other tissues receive some dose from secondary 

radiation. Secondary radiation consists of X-rays that are scattered from surrounding materials or that 

escape from the source assembly. This technical basis document (TBD) includes tables that list

claimant-favorable estimated dose equivalents to organs of the body that result from single and 

combined PA and LAT chest X-rays for male and female PGDP employees. The tables are derived 

from an assessment of the air kerma at the source-to-skin distance (SSD), based on specific 

operating parameters for the facility, insofar as these are known.

3.2 EXAMINATION FREQUENCIES

Each X-ray examination consisted of one PA and one LAT chest view. Table 3-1 lists the minimum

criteria for examination frequencies for PGDP employees. This policy has been in place since before 

1974, with the exception of the criterion for asbestos workers, which started in about 1986. Some 

lumbar spine projections might have been made in the early days. These are addressed in 

Attachment 3B. 

Table 3-1. Frequency of chest X-ray 

examinations. 

Employees Frequency

Nonsmokersa Every 5 years

Smokers under age 40 Every 5 years

Smokers age 40 and older Every 3 years

Asbestos workersb Every 2 years

a. Ex-smokers are considered as smokers for 10 

years after quitting.

b. Program started about 1986.

Regular repeat/retake analyses for the X-ray department have been performed for a number of years. 

There is no indication that the repeat rate has been of any significance. Occasional X-ray exposures, 

as for a possible broken bone, are not included in the occupational dose reconstruction because they 

are not considered a requirement for employment. There is no evidence that fluoroscopy was ever 

used for required chest X-ray examinations. 

3.3 EQUIPMENT AND TECHNIQUES

Table 3-2 lists the diagnostic medical X-ray equipment used at PGDP during specified periods. The 

initial General Electric (GE) machine was used from the opening of the plant in 1952 through February 

1975. It was replaced by the Picker unit, which served from March 1975 through December 1995. 

The present equipment has been in operation since January 1996. Quality assurance (QA) has been 

verified regularly by the Food and Drug Administration and the State of Kentucky, as well as by inhouse surveys. Interviews with the staff provided much of the information in this TBD. The X-ray 

facility has been operated by the present technician since November 1974.
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Table 3-2. PGDP X-ray equipment. 

Period Equipment

1952–Feb. 1975 GE, some filtration, manual collimator, stationary grid, no 

phototiming, hand-developed film

Mar. 1975–Dec. 1995 Picker, filtration, automatic collimator, Bucky grid, DuPont 

cassettes and screen, phototiming, automatic film development 

Jan. 1996–present XMA Linear II Eureka, filtration, automatic collimator, Bucky 

grid, phototiming, automatic film development

The dose received from a diagnostic X-ray exposure depends on a number of factors. These include 

filtration, collimation, and the use of grids, as well as the projection and the size and positioning of the 

subject. Machine settings determine the peak voltage (kVp), current (mA), and exposure time, which 

can be selected for optimum imaging with minimum dose. With the two most recent machines (see 

Table 3-2), exposures were controlled by phototiming. This permits accurate termination of the 

exposure when the subject has received a predetermined amount of radiation needed for a particular 

radiograph. Timing for the GE machine was determined by using standard charts and taking patient 

size into account. This might have resulted in more exposure to some patients, and the claimantfavorable dose values used in this TBD take this into account.

Table 3-3 lists nominal operating parameters for the three machines, all of which are single-phase, for 

PA and LAT projections. The GE equipment operated in the range from 70 to 90 kVp, and the newer 

machines in the range from 90 to 100 kVp. All three used a current of 300 mA. From March 1975 to 

the present, the dose with either of the two more recent machines listed in Table 3-2 has been 

comparable for a given procedure. Therefore, organ dose equivalents are determined for two periods: 

1952 to February 1975 and March 1975 to the present.

Table 3-3. Operating parameters. 

Period Projection kVp (V) Current (mA)

1952–Feb. 1975 PA 70–90 300

LAT 70–90 300

Mar. 1975–Dec. 1995 PA 90–100 300

LAT 90–100 300

Jan. 1996–present PA 90–100 300

LAT 90–100 300

Other factors being equal, the air kerma and resultant organ doses are proportional to the timeintegrated current (mAs). Some measurements of mAs were conducted with the present equipment 

for PA and LAT views of 16 males and 4 females with body sizes classified as “large,” “medium,” and 

“small.” Table 3-4 summarizes the results, listing average values of mAs in each classification and for 

all 20 persons in the sample. Although the number of subjects is small, the trend toward larger mAs 

with increasing body size is seen for both sexes. Larger values for males are evident. The kerma 

estimation in Section 3.4 uses the average for the 10 medium male workers from Table 3-4 for all

employees. Rounded off, these values are, respectively, for the PA and LAT views,

= 16 mAs and = 64 mAs . − )13.3( QPA QLAT

As described at the end of Section 3.4.1, actual measurements (Gregory 2003) indicate that the 

kerma calculated from these values is about 50% larger than the actual value (claimant-favorable). 
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Table 3-4. Average mAs for exposures of workers of 

different body size. 

Body size

(number males, females) View

Males

(mAs)

Females

(mAs)

Large

(3 m, 0 f)

PA 26.9 -

LAT 145. -

Medium

(10 m, 2 f)

PA 15.9 14.3

LAT 64.4 47.5

Small

(3 m, 2 f)

PA 10.3 6.2

LAT 61.8 19.9

All persons

(16 m, 4 f)

PA 17.7 10.3

LAT 79.0 33.7

3.4 ORGAN DOSE CALCULATIONS

The calculation proceeds in two steps: determination of the air kerma at the entrance to the skin, and 

conversion of this quantity to dose equivalent in different organs. Table B.3, p. 99, of National Council 

on Radiation Protection and Measurements (NCRP) Report 102 (NCRP 1989) lists values of the air 

kerma (more precisely, the air kerma in air) per mAs at different distances from the source (X-ray 

focal point) and for different kVp values with a total filtration equivalent to 2.5 mm Al. As stated in 

Section 3.3, doses for the two more recent PGDP X-ray machines are comparable. The discussion in 

Section 3.4.1 determines the air kerma at skin entrance, applicable to both machines for the period 

from March 1975 to the present, by using Table B.3 from NCRP (1989). The discussion in Section 

3.4.2 assesses the air kerma for the GE equipment, applicable for the period from 1952 to 

March 1975, by other means. For both periods, this assessment used dose conversion factors from 

International Commission on Radiological Protection (ICRP) Publication 34 (ICRP 1982) in Sections 

3.4.3 and 3.4.4 to evaluate the dose equivalent in various organs.

3.4.1

With an average tube potential of 95 kVp, consistent with Table 3-3, one obtains directly by linear 

interpolation from Table B.3 of NCRP (1989) (total filtration equivalent to 2.5 mm Al) the air kerma 

value Ko = 0.19 cGy/(100 mAs) for single-phase generators at a source-to-image distance (SID) ro = 

183 cm (= 72 in). It will be convenient to work with the following units:

Air Kerma for Exposures from March 1975 to Present

1 .(109.1 )11.4.3( 100

19.0 3 = × ×= − 1- − 1-

o cGyrad mAs)rad mAs

cGy K

For an exposure made with Q mAs, the kerma at a distance r is given by

.rad (3.4.1- 2) o

o Q

r

r KrQK

2

),( 



 



 =

The square of the distance ratio adjusts for the inverse-square dependence of the kerma over the 

range of distances considered.

For the PA view, an allowance of 5 cm is made for cassette thickness and 26 cm for chest thickness 

between the source and image. Therefore, the SSD is rPA = 183 – 31 = 152 cm. For the LAT 

projection with an assumed chest thickness of 34 cm, rLAT = 183 – 39 = 144 cm. Thus,
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= 152 cm and = 144 cm . − )31.4.3( PA LAT r r

With ro = 183 cm, one obtains from equations 3.4.1-1 through 3.4.1-3 the following values for the 

kerma at skin entrance for the two projections,

mAs) 44 rad (3.4.1- 4) mAs

rad

PA 16( 0.0

152

109.1 183 3 2

 = 

 



×  =

−

K

and

mAs) .rad (3.4.1- 5) mAs

rad

LAT 64( 20.0

144

109.1 183 3 2

 = 

 



×  =

−

K

These estimates of air kerma at skin entrance apply to exposures made from March 1975 to the 

present.

The kerma estimate (equation 3.4.1-4) for the PA view can be compared directly to measurements 

made during an in-house radiation safety survey of the PGDP X-ray facility in June 2003 (Gregory

2003). The exposure measured in the beam at a distance of 183 cm was 19 mR. The value of the 

kerma at this distance implied by equation 3.4.1-4 is 30 mrad, which is consistent with an exposure 

close to 30 mR, approximately 1.5 times larger than the measured value. Using NCRP (1989) with a 

total filtration of 3.8 mm Al leads to the calculated kerma value of 0.019 rad at 183 cm. Thus, the 

estimate (equation 3.4.1-4) is probably higher than the actual value by about 50%, due to greater 

filtration than that assumed. However, as applied to PA views for all persons in this TBD, KPA = 0.044 

rad, which is claimant-favorable, is used.

3.4.2

Detailed information and technical data for operation of the original X-ray installation at PGDP are 

limited. Default values for skin-entrance kerma have been developed for use in such instances by 

Kathren et al. (2003). These take into account common practices of the day, limited filtration and 

collimation, low kVp, slow film speeds, and patient dose studies reported in the literature. With 

conservative assumptions, the default values probably were approached only rarely in an actual 

exposure. The default kerma values of Kathren et al. (2003) for pre-1970 conditions are used in this 

TBD. They are listed in Table 3-5, together with the values given by equations 3.4.1-4 and 3.4.1-5.

Air Kerma for Exposures from 1952 through February 1975

Table 3-5. Air kerma at skin entrance 

for PA and LAT views. 

Dates

Kerma (rad)

PA LAT

1952–Feb. 1975 0.20 0.50

Mar. 1975–present 0.044 0.20

3.4.3

Tables A2 through A9 in ICRP (1982) list average values of absorbed doses in seven selected organs 

and the total body per unit entrance kerma (i.e., air kerma in air with no backscatter). For example, 

the dose equivalent to the active bone marrow is computed for the values of the kerma in Table 3-5. 

Dose Equivalents per Exposure for Organs Included in ICRP Publication 34
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Absorbed dose values for active bone marrow are listed in Table A8, p. 59, of ICRP (1982) for 

different beam qualities, expressed as the half-value layer (HVL) in mm Al. Claimant-favorable 

values, 2.5 mm Al for the time period 1952-Feb. 1975 (Kathren et al. 2003) and 3.5 mm Al for Mar. 

1975-present, are assumed. With a quality factor of unity for X-rays, the numbers in the ICRP (1982) 

tables, listed in mGy (organ absorbed dose) per Gy (entrance kerma), are numerically equal to mrem 

of organ dose equivalent per rad of entrance kerma. It follows, therefore, that multiplication of the 

kerma in rad from Table 3-5 by the numbers in the ICRP (1982) tables yields the organ dose 

equivalents H in mrem directly. In other words, 

K rad)( × ICRP Value = H .(mrem) (3.4.3 -1)

With an SID of 183 cm and the two assumed beam qualities, one obtains from Table A8 of ICRP 

(1982) the values needed to compute the organ dose equivalents for (male/female) PA and LAT chest 

projections. With the entrance kerma from Table 3-5, the following summarizes the dose equivalent 

to the active bone marrow for the four cases:

1952 to February 1975

PA: 0.20 × 92 = 18. mrem (males) LAT: 0.50 × 37 = 19. mrem (males)

0.20 × 86 = 17. mrem (females) 0.50 × 29 = 15. mrem (females)

March 1975 to Present

PA: 0.044 × 146 = 6.4 mrem (males) LAT: 0.20 × 61 = 12 mrem (males)

0.044 × 141 = 6.2 mrem (females) 0.20 × 48 = 9.6 mrem (females).

For the period 1952 to February 1975, these dose equivalents agree with the values given by Kathren 

et al. (2003). These are the first entries in Table 3-6. In principle, the rest of the table is calculated in 

similar fashion. However, ICRP 34 applies to collimated beams, and would thus likely underestimate 

the doses to some organs for the earlier period, 1952-Feb. 1975. Some organs not in the chest 

cavity, such as the ovaries, testes, thyroid, and uterus, could be exposed to the primary beam if the 

collimation is poor. For 1952-Feb. 1975, the dose conversion factors of Kathren et al. (2003) for pre1970 are used.

Table 3-6. Dose equivalent per PA and per LAT exposure for 

organs included in ICRP Publication 34. 

Organ

Dose equivalent (mrem)a

1952–Feb. 1975 Mar. 1975–present

PA LAT PA LAT

Bone marrow (active) 18. (m)

17. (f)

19. (m)

15. (f)

6.4 (m)

6.2 (f)

12. (m)

9.6 (f)

Breast (female) 9.8 130. 4.0 63.

Lungs 84. (m)

90. (f)

97. (m)

110. (f)

25. (m)

27. (f)

55. (m)

62. (f)

Ovaries 25. 13. 0.14 0.32

Testes 5.0 2.5 0.0004 0.02

Thyroid 35. 69. 2.7 30.

Uterus (embryo) 25. 13. 0.13 0.28

a. (m) denotes male; (f), female

3.4.4

For estimating dose equivalents with the Interactive RadioEpidemiological Program (IREP) for organs 

not included in ICRP (1982), these organs are classified in three anatomical regions, as listed in the 

Dose Equivalents per Exposure for Organs not Included in ICRP Publication 34
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first column of Table 3-7. In the second column, a single organ from ICRP (1982) is selected from 

Table 3-6 as representative of the dose to all organs in that region. Column three lists other body 

organs according to the region in which they are located. With the exception of the skin in the last 

row, they are assigned the dose equivalent from Table 3-6 for the organ listed in column two. For the 

lungs, the slightly larger values for females from Table 3-6 are used for both sexes. The ICRP 

Table 3-7. Dose equivalent per PA and per LAT exposure for organs not included 

in ICRP Publication 34. 

Anatomical

region

ICRP 34

organ Other organs

Dose equivalent (mrem)

1952–Feb. 1975 Mar. 1975–present

PA LAT PA LAT

Thorax Lungs Bone surface

Esophagus

Liver/gall 

 bladder/spleen

Remainder organs

Stomach

Thymus

90. 110. 27. 62.

Abdomen Ovaries Colon/rectum

Urinary/bladder

 25. 13. 0.14 0.32

Head/neck Thyroid Eye/brain 6.4 69. 2.7 30.

Skin 270. 680. 140. 340.

“remainder organs” (ICRP 1991) are assigned to the group (thorax) with the largest dose equivalent. 

The skin is the only organ listed in Table 3-7 that does not involve ICRP (1982) dose conversion 

factors. The estimated dose equivalent is numerically equal to the product of the entrance kerma 

(Table 3-5) and a backscatter factor based on Table B.8 of NCRP (1989). Kathren et al. (2003) have 

calculated default skin dose equivalents for pre-1970, 1970-1980, and post 1980. Their pre-1970 

values are used in this TBD for the time period 1952 to February 1975 and their 1970-1985 values for 

the time period March 1975 to present.

3.4.5 

The regular diagnostic X-ray examinations at PGDP consisted of one PA and one LAT exposure. The 

estimated resultant total organ dose equivalents per examination are listed in Table 3-8. With the 

exception of the skin (last row), which does not depend on ICRP (1982), these values are the sums of 

the respective dose equivalents from Tables 3-6 and 3-7. If two sets of values, (m) and (f), appear in 

Table 3-6, the larger sum was entered in Table 3-8. For the skin, two estimates were made for 

consideration in each period for Table 3-8 as follows. During the period from March 1975 to the 

present, when both PA and LAT views were made, the posterior skin (Table 3-7) received a dose 

equivalent of 140. mrem (with backscatter) from the PA view plus radiation entailed from the LAT view 

(without backscatter). The latter component of the posterior skin dose equivalent is roughly 

approximated by the LAT lung dose equivalent, which from Table 3-7 is 62. mrem. This estimate 

gives a dose equivalent of 140. + 62. = 200. mrem for the posterior skin when both views are made. 

Using the same prescription for LAT skin gives a dose equivalent of 340. + 27. = 370. mrem. The 

claimant-favorable larger estimate was selected for the last row in Table 3-8 for the combined 

exposure of the skin in the period from March 1975 to the present. A similar computation leads to the 

value of 770. mrem for the period from 1952 to February 1975.

Combined Dose Equivalents for PA and LAT Exposures
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Table 3-8. Organ dose equivalents for combined PA and 

LAT examinations. 

Organ

Dose equivalent (mrem)

1952-Feb. 1975 Mar. 1975-present

Bone marrow (active) 37. 18.

Bone surface 200. 89.

Breast (female) 140. 67.

Colon/rectum 38. 0.46

Esophagus 200. 89.

Eye/brain 75. 33.

Liver/gall bladder 200. 89.

Lungs 200. 89.

Ovaries 38. 0.46

Remainder 200. 89.

Stomach 200. 89.

Testes 7.5 0.02

Thymus 200. 89.

Thyroid 100. 33.

Urinary/bladder 38. 0.46

Uterus (embryo) 38. 0.41

Skin 770. 370.

3.5 UNCERTAINTY

For the period from 1952 to February 1975, the values listed in Tables 3-6 and 3-7 are based on 

claimant-favorable assumptions described by Kathren et al. (2003). For further conservatism, these 

authors suggest that a positive error of +30% be used. 

For the period from March 1975 to the present, sources of uncertainty in patient organ dose 

equivalents are included in Table 3-9. The first column lists, from top to bottom, the sequential steps 

by which the values in Tables 3-6 and 3-7 were obtained. The second column characterizes the 

potential significance of these values in terms of uncertainties they might introduce. Knowledge of 

actual organ dose equivalents for a given procedure is uncertain because of both physical factors and 

variations among different individuals. 

As summarized in the first row of Table 3-9, organ dose equivalent estimations for the original PGDP 

X-ray machine (before March 1975) are considered upper limits, based on knowledge of machines 

and practices of the time. Much better characterization of the radiation field is known for the two later 

machines. In the second row, the physical data in NCRP (1989) have been shown to have little error. 

The assessment of 10% accuracy for patient dose (Zamenhof, Shahabi, and Morgan 1987) could 

reflect variations among patients.

With other conditions fixed, any uncertainties in the kVp, tube current and exposure time, and 

placement of the individual in the X-ray beam contribute to uncertainty in the kerma at skin entrance 

(Table 3-9, third row). Based on NCRP (1989), the kerma was calculated from equation 3.4.1-2. By 

assigning values for uncertainties as coefficients of variation (ratio of the standard deviation and 

mean) for r, Q, and the tube potential, one can apply error-propagation formalism to estimate the 

resultant coefficient of variation for the kerma. This procedure is described in Attachment 3A. For 

uncertainties of 10% in r and 5% in Q and the voltage, it is suggested that KPA = 0.044 ±0.015 rad at 

the 95% confidence level. The estimated uncertainty in the kerma values at skin entrance for March
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1975 to the present (last row in Table 3-5) is no more than 35%, attributable primarily to differences 

among patients and their placement.

Table 3-9. Potential sources of uncertainty in organ dose equivalent assessments. 

Source Assessment

Equipment and techniques; 

Section 3.3

GE machine (1952-Feb. 1975): little documentation. Use conservative 

default values (Kathren et al. 2003).

Newer machines (Mar.1975-present): little uncertainty in knowledge of 

radiation field, verified by independent surveys. Use technique factors.

NCRP (1989), Section 3.4 Table B.3 of NCRP (1989) lists air kerma per mAs at different distances for 

various kVp and filtration from measurements of Zamenhof, Shahabi, and 

Morgan (1987), which states average accuracy of 0.3% for fit to 

measurements and 10% for patient-dose validation.

Air kerma K at skin entrance, eq. 

3.4.1-2, Table 3-5 

Ko determined by tube voltage and Q by current and time with relatively 

little error. Distance r from source to skin subject to considerable variation 

because of patient size and placement. Analysis (Attachment 3A) indicates 

net uncertainty in K due to these factors by perhaps as much as 35%.

ICRP (1982), Table 3-6 for ICRP 

34 organs, Table 3-7 for other 

organs

ICRP 34 tables for organ absorbed doses per unit entrance kerma are 

derived from Monte Carlo calculations for anthropomorphic phantom 

(Gorson, Lassen, and Rosenstein 1982). Additional uncertainties in actual 

organ dose equivalents introduced in this step include differences between 

mathematical model and actual organs and individual anatomical variations 

among persons. Rough estimate of uncertainty, 50%.

In the last row of Table 3-9, the same conversion factors from entrance kerma to organ doses are 

used for all individuals, a distinction being made between male and female for some organs. In any 

case, the conversion factors are representative for an exposed individual (for the assumed kerma) to 

the extent that the anatomical features of the individual match those of the phantom on which the 

tables are based. The variation introduced in this step is not known. An indication can be gained 

through comparison with dose conversion factors in ICRP (1982) for the 5-year-old pediatric phantom 

under the same irradiation conditions. Doses in the smaller phantom per unit entrance kerma are 

often larger by factors approaching two. Roughly, it is estimated that uncertainty due to adult patient 

variability might be as large as 50%.

In summary, there is relatively little uncertainty associated with the first two steps in Table 3-9. The 

third and fourth steps entail, sequentially, estimated uncertainties of 35% and 50%. In the worst case, 

these would act fully in the same direction to increase the error. An exposure could then give a dose 

equivalent for some individuals that is larger than those listed in Tables 3-6 and 3-7 for the period 

from March 1975 to the present by the factor 1(1.35)(1.50) = 2. It is estimated conservatively that 

uncertainty in the values of the dose equivalent for this period in Table 3-8 is not more than a factor of 

two.

3.6 DOSE RECONSTRUCTION

3.6.1 

The normal occupational chest X-ray examination at PGDP consisted of a single PA and a single LAT 

exposure. Table 3-10 provides claimant-favorable estimates, allowing for uncertainty, of organ dose 

equivalents per examination that can be used for dose reconstruction. The total dose equivalent to an 

organ of a worker is the product of the value in Table 3-10 and the number of examinations the worker 

underwent during each period, including a preemployment examination. The minimum frequency of

Claimant-Favorable Organ Dose Equivalents per Examination
Effective Date: 02/05/2004 Revision No. 00 Document No. ORAUT-TKBS-0019-3 Page 13 of 20

chest X-ray examinations is listed in Table 3-1. Dose reconstruction for a lumbar spine examination 

(possible in the early days) is given in Attachment 3B.

Except for skin, which does not depend on ICRP (1982) (see Section 3.4.4), the values in Table 3-10

for the period from 1952 to February 1975 are 1.3 times the values listed in Table 3-8. They thus 

reflect the claimant-favorable +30% error assessed by Kathren et al. (2003), as stated at the 

beginning of Section 3.5.. Dose equivalents for the period from March 1975 to the present are twice 

the estimated values from Table 3-8. This factor reflects the client-favorable estimate of uncertainty 

described at the end of Section 3.5. 

Table 3-10. Claimant-favorable organ dose equivalents per 

examination consisting of one PA and one LAT exposure. 

Organ Dose equivalent (mrem)

1952-Feb. 1975 Mar. 1975-present

Bone marrow (active) 48. 36.

Bone surface 260. 180.

Breast (female) 180. 130.

Colon/rectum 49. 0.92

Esophagus 260. 180.

Eye/brain 98. 66.

Liver/gall bladder/spleen 260. 180.

Lungs 260. 180.

Ovaries 49. 0.92

Remainder 260. 180.

Stomach 260. 180.

Testes 9.8 0.04

Thymus 260. 180.

Thyroid 130. 66.

Urinary/bladder 49. 0.92

Uterus 49. 0.82

Skin 770. 370.

3.6.2

It is sometimes useful to establish initially if a given exposure history indicates that the levels warrant 

precise evaluation. In Table 3-11, organs other than skin have been divided into three groups. Each 

organ in a group has been assigned a dose equivalent that is no smaller than its value in Table 3-10. 

Optional Initial Screening

Table 3-11. Upper-bound organ dose equivalents per examination for

screening. 

Organ

Dose equivalent (mrem)

1952-Feb. 1975 Mar. 1975-present

Colon/rectum, ovaries, testes, 

urinary/bladder, uterus 

49. 0.92

Bone marrow (active), eye/brain, thyroid 180. 66.

Bone surface, breast (female), 

esophagus, liver/gall bladder/ spleen, 

lungs, remainder, stomach, thymus

260. 180.

Skin 770. 370.
Effective Date: 02/05/2004 Revision No. 00 Document No. ORAUT-TKBS-0019-3 Page 14 of 20

Therefore, the shorter Table 3-11 can be used to estimate a claimant-favorable upper bound for an 

organ dose equivalent per examination. Unless the records indicate that more frequent X rays were 

provided, the expected number of examinations can be based on Table 3-1. Assume a 

preemployment examination, followed by a regular examination every 3 years thereafter, whether the 

worker was a smoker or not until 1986. Beginning at the start of 1986, assume that the examination 

frequency changes to every 2 years to be claimant-favorable. 

Example.

5 × 180. + 9 × 66. = 1500. mrem.

 Calculate an upper bound for the dose equivalent to the active bone marrow of a worker. 

The individual was hired on February 1, 1962, and worked steadily until retirement on March 31,

1996. Determine the number of examinations during each of the two periods and apply Table 3-11. 

Without making a distinction for smoking, assume initially an examination every 3 years around 

February 1. The length of employment was 34 years and 2 months. Starting with the preemployment 

examination, there would be a total of five made with the older GE equipment: the preemployment 

examination plus those in 1965, 1968, 1971, and 1974. Those after February 1974 were with the 

more recent equipment. Four were made through 1986 (every 3 years) and five from 1988 through 

1996 (every 2 years), for a total of nine with the more recent equipment. An upper bound for the dose 

equivalent to the active bone marrow, based on Table 3-11, is 
Effective Date: 02/05/2004 Revision No. 00 Document No. ORAUT-TKBS-0019-3 Page 15 of 20

REFERENCES

Gregory, W. D., 2003, Report on Survey of Medical X-Ray Unit, Paducah Gaseous Diffusion Plant.

Gorson, R. O., M. Lassen, and M. Rosenstein, 1982, “Patient Dosimetry in Diagnostic Radiology,” in 

Handbook of Medical Physics, R. G. Waggener, ed., CRC Press, Boca Raton, Florida.

Kathren, Ronald L., Vernon E. Shockley, Elyse M. Thomas, and Timothy D. Taulbee, 2003, Dose 

Reconstruction from Occupationally Related Diagnostic X-Ray Procedures, ORAUT-TIB-0006

(Rev. No. 02-A), National Institute for Occupational Safety and Health, Office of Compensation 

Analysis and Support, Cincinnati, Ohio. 

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

Diagnostic Radiology, Publication 34, Pergamon Press, Elsmford, New York.

ICRP (International Commission on Radiological Protection), 1991, 1990 Recommendations of the 

ICRP, Publication 60, Pergamon Press, Elsmford, New York.

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

Beam and Gamma-Ray Protection for Energies up to 50 MeV, Report No. 102, Bethesda, 

Maryland.

Zamenhof, R. G., S. Shahabi, and H. T. Morgan, 1987, “An Improved Method for Estimating the 

Entrance Exposure in Diagnostic Radiographic Examinations,” American Journal of 

Roentgenology, Volume 149, pp. 631-637.
Effective Date: 02/05/2004 Revision No. 00 Document No. ORAUT-TKBS-0019-3 Page 16 of 20

GLOSSARY

absorbed dose

Energy absorbed per unit mass; units are rad and gray (Gy).

backscatter (radiation)

Radiation that is scattered backwards, enhancing skin dose where an X-ray beam 

normally enters the body. 

dose equivalent

Product of absorbed dose and quality factor or radiation weighting factor. With dose in 

rad, unit is rem; with dose in Gy, unit is sievert (Sv).

gray (Gy)

Unit of absorbed dose (1 Gy = 1 J kg-1 = 100 rad).

kerma

Sum of initial kinetic energies of all charged particles (including Auger electrons) 

liberated by uncharged radiation per unit mass. Units are rad and Gy.

primary X-rays

X-rays that constitute the useful beam that emerges from the tube target.

rad

Unit of absorbed dose (1 rad = 100 erg g-1 = 0.01 Gy).

rem

Unit of dose equivalent.

secondary radiation

As distinct from primary X radiation, secondary radiation consists of X-rays that have 

been scattered from objects or that leak from the source assembly.

sievert (Sv)

Unit of dose equivalent.

X-ray

Ionizing electromagnetic radiation of non-nuclear origin; also, a radiograph.
Effective Date: 02/05/2004 Revision No. 00 Document No. ORAUT-TKBS-0019-3 Page 17 of 20

ATTACHMENT 3A 

ERROR PROPAGATION FOR KERMA

The kerma at skin entrance distance for the two newer machines used from March 1975 to the 

present (Table 3-5) is calculated from equation 3.4.1-2. Given values for uncertainties in r, Q, and the 

tube potential, a standard formalism for error propagation (Taylor 1997; Tsoulfanidis 1983) can be 

applied to estimate the uncertainty in K that results. Because the beam intensity is approximately 

proportional to the 1.7 power of the tube potential V, one can make the replacement,

C -A 1) oo , ( 7.1 = VK

where Co is the constant of proportionality, in equation 3.4.1-2. To show the explicit dependence of 

the kerma on these quantities, one can then write in place of equation 3.4.1-2,

),,( . )2(

2

7.1  − 

 



 = C A o

o Q

r

r VQrVK

For the analysis, it is convenient to employ uniform notation for the variables, defined by writing

V = X1 with mean μ1 = μV and standard deviation σ1 = σV

r = X2 with mean μ2 = μr and standard deviation σ2 = σr

Q = X3 with mean μ3 = μQ and standard deviation σ3 = σQ . 

The kerma can be written

),,( . )3( 2

2

3

7.1

1

321 = C A − 2

oo X

XX

rXXXK 

Given estimated uncertainties σi in the Xi

, the task is to estimate the resulting uncertainty σK in K. 

According to the formalism, one approximates the kerma (equation A-3) by making a Taylor series 

expansion about the point μ = (μ1, μ2, μ3) and retaining only the linear terms. The variables are 

assumed to be independent. It follows that

. )4( 2

2 3

1

2 − 















∂

∂

≅ ∑=

i A

i i

K X

K

σ σ

μ

The partial derivatives are to be evaluated at the point μ. Carrying out the differentiations from 

equation A-3 and substituting into equation A-4 gives

( ) C -A 5)

0.7

2 1

oo ( 7.1 2 2

3

2

2

2

7.1

2 1

2

2

3

2

3

7.1

2 1

1

2

2

2

3 2 2

































+ 













 − + 















≅ σ

μ

μ σ

μ

μμ σ

μ

μμ σ r K

( ) C -A 6) 2

oo .2 89 4 (

2

3

3

2

2

2

3

7.1

1

2

2

2

2

2

2

3

7.1

1

2

1

1

2

2

2

3

7.1

1 2

















































+ 































+ 































≅

μ

σ

μ

μμ

μ

σ

μ

μμ

μ

σ

μ

μμ

r
Effective Date: 02/05/2004 Revision No. 00 Document No. ORAUT-TKBS-0019-3 Page 18 of 20

.2 89 4 . )7(

2

3

3

2

2

2

2

1

1

2

2

2

3

7.1

1 − 































+ 















+ 































≅ C A 2

oo μ

σ

μ

σ

μ

σ

μ

μμ

r

Comparison of the factor outside the bracket with equations A-2 and A-3 shows that it is the square of 

the kerma K(μ) at the point μ. Returning to the original notation with Ko, r, and Q, one can write in 

place of the last equation,

89.2 4 . ( -A 8) )(

2

1

2 2 2

































+ 















+ 















≅

Q

Q

r

r

V

K V

K μ

σ

μ

σ

μ

σ

μ

σ

The ratio of the standard deviation (standard error) and the mean is called the coefficient of variation, 

which for the kerma can be denoted by cK = σK/μK. With similar notation for the coefficients of 

variation for the other variables, equation A-8 can be written

-A 9) 2 .2 89 .4 ( 2 2

K QrV c ++≅ ccc

This result provides an estimate of the uncertainty of the kerma in terms of the uncertainties in V, r, 

and Q. The approximation is best to the extent that the σi << μi. 

Values of the operating parameters used to obtain KPA = 0.044 rad, equation 3.4.1-4, can be used as 

estimates for the quantities needed in equation A-9. For orientation, it will be assumed that the 

voltage V and mAs Q have standard errors of ±5%. An uncertainty in the SSD r of 10 cm, or ±7% with 

r = 152 cm, will be assumed to allow for anatomical and placement variations. With cV = cQ = 0.05 

and cr = 0.07, equation A-9 gives cK ≅ 0.17. Thus, the estimated standard error of the PA kerma is 

0.17 × 0.044 = 0.007 rad. With assumed normal statistics, KPA = 0.044 ±0.015 rad at the 95% 

confidence level (1.96σ). That is to say, the probability is 0.95 that the true value of the kerma (which 

is unknown) is in the stated range. The interval width is ±34%. With other reasonable assumptions, it 

appears that the largest contributor to uncertainty in row three of Table 3-9 rises from variations in the 

SSD. Use of Tables 3-6 and 3-7 implies that r = 152 cm for all persons. The uncertainty in the kerma 

at skin entrance is assumed to be no greater than about 35%.

REFERENCES

Taylor, J. R., 1997, An Introduction to Error Analysis, second edition, University Science Books, 

Sausalito, California.

Tsoulfandis, N., 1983, Measurement and Detection of Radiation, Hemisphere Publishing Co. 

(McGraw-Hill), New York, New York.
Effective Date: 02/05/2004 Revision No. 00 Document No. ORAUT-TKBS-0019-3 Page 19 of 20

ATTACHMENT 3B 

ORGAN DOSE EQUIVALENTS FOR LUMBAR SPINE EXAMINATIONS

Lumbar spine examinations might have occurred in the early days at PGDP, certainly before 1974, 

when the present X-ray technician was hired. They could have been made as a preemployment

requirement, a practice in some industries at the time.

There is no specific information available for dose reconstruction other than that described in Tables 

3-2 and 3-3 for the original GE machine. It is assumed that an examination consisted at most of five 

exposures: one anterior-posterior (AP), one lateral (LAT), two oblique, and one spot film. Operating 

voltage and current are assumed to be 90 kVp and 300 mA, with exposure times of 1 s for AP and 1.5 

s for LAT, respectively. Under these conditions, the organ dose equivalents can be calculated for 

these two views by the method used in this TBD. ICRP (1982) does not include the other three. In 

the absence of other information, initial organ dose equivalents HLS to be used for lumbar spine dose 

reconstruction are estimated to be those from all five views, roughly approximated as 2.5 times the 

sum of the AP and LAT dose equivalents. Values of HLS are given in Table B-1. 

The calculation proceeds as in the main document. Analogous to equation (3.3-1), one has for the 

lumbar spine examination

mA)(1 s) 300 mAs and mA)(1.5 s) 450 mAs . QAP = (300 = QLAT = (300 = 

(B-1)

As before, a 5-cm thickness is allowed for the cassette. The same body thicknesses of 26 cm and 34 

cm, respectively, are assumed for the AP and LAT views. The lumbar spine SID = 102 cm (ICRP 

1982). Therefore, for the SSD,

 cm and cm . AP LAT r =−= 7131102 r =−= 6339102 (B-2)

From Table B.3 in (NCRP 1989), one finds for the kerma at the distance ro = 60 cm,

 1 016.0 . 6.1 1- 1-

o rad cGy rad (mAs) 100 mAs 

cGy K = × = (B-3)

The kerma values at skin entrance for the two views are

 mAs) 3.4 rad

mAs

rad

AP  = 

 



 = 300( 71

016.0 60 2

K (B-4)

and

 mAs) 6.5 rad . mAs

rad

LAT  = 

 



 = 450( 63

016.0 60 2

K (B-5)

The procedures used for calculating the organ dose equivalents in Tables 3-6 and 3-7 were applied to 

the lumbar spine AP and LAT views for the GE machine in use from 1952 to February 1975. As in 

(Kathren et al. 2003), a beam quality HVL of 2.5 mm Al was assumed, and substitute projections were 

used for some organs to approximate the lack of good collimation. The total dose equivalents HLS for 
Effective Date: 02/05/2004 Revision No. 00 Document No. ORAUT-TKBS-0019-3 Page 20 of 20

the thyroid and eye/brain were estimated to be in the same ratios to the thymus as in Table 3-8. The 

dose equivalents for the breast were approximated by those for the lung. The resulting estimates of 

the organ dose equivalents HAP and HLAT calculated for the two lumbar spine views are given in Table 

B-1. The last column gives the estimated organ dose equivalents for the total of five assumed 

exposures, approximated by

 (5.2 .) HLS = AP + HH LAT (B-6) 

These values for HLS can be used as rough first approximations for lumbar spine dose reconstruction 

in the absence of other information.

 Table B-1. Organ dose equivalents for lumbar spine examinations.

Organ

Dose equivalent (mrem)

HAP HLAT HLS

Bone marrow (active) 130. 140. 680.

Bone surface 270. 91. 900.

Breast (female) 270. 91. 900.

Colon/rectum 790. 370. 2900.

Esophagus 270. 91. 900.

Eye/brain --- --- 340.

Liver/gall bladder 270. 91. 900.

Lungs 270. 91. 900.

Ovaries 790. 370. 2900.

Remainder 270. 91. 900.

Stomach 270. 91. 900.

Testes 61. 21. 210.

Thymus 270. 91. 900.

Thyroid --- --- 450.

Urinary/bladder 790. 370. 2900.

Uterus 1000. 280. 3200.