ORAU TEAM

Dose Reconstruction

Project for NIOSH

Oak Ridge Associated Universities I Dade Moeller & Associates I MJW Corporation

Page 1 of 13

Document Title:

Lawrence Livermore National Laboratory – 

Occupational Medical Dose

Document Number: ORAUT-TKBS-0035-3 

Revision: 00

Effective Date: 08/22/2005

Type of Document: TBD

Supersedes: None

Subject Expert: James E. Turner

Document Owner

Approval: Signature on File Approval Date: 08/15/2005

Jay J. Maisler, TBD Team Leader

Approval: Signature on File Approval Date: 08/15/2005

Judson L. Kenoyer, Task 3 Manager

Concurrence: Signature on File Concurrence Date: 08/16/2005

Richard E. Toohey, Project Director

Approval: Signature on File Approval Date: 08/22/2005

James W. Neton, Associate Director for Science

 New Total Rewrite Revision Page Change

DOCUMENTS MARKED AS A TOTAL REWRITE, REVISION, OR PAGE CHANGE REPLACE THE PRIOR REVISION. 

PLEASE DISCARD / DESTROY ALL COPIES OF THE PRIOR REVISION.
Document No. ORAUT-TKBS-0035-3 Revision No. 00 Effective Date: 08/22/2005 Page 2 of 13

PUBLICATION RECORD

EFFECTIVE 

DATE

REVISION 

NUMBER DESCRIPTION

04/15/2005 00-A New technical basis document for the Lawrence Livermore National 

Laboratory – Occupational Medical Dose. Initiated by Jay J. Maisler.

06/02/2005 00-B Incorporates internal review comments. Initiated by Jay J. Maisler.

06/22/2005 00-C Incorporates resolution of NIOSH review comments. Initiated by Jay 

J. Maisler.

08/08/2005 00-D Incorporates resolution of additional NIOSH review comments. 

Initiated by Jay J. Maisler.

08/22/2005 00 First approved issue. Training required: As determined by the Task 

Manager. Initiated by Jay J. Maisler.
Document No. ORAUT-TKBS-0035-3 Revision No. 00 Effective Date: 08/22/2005 Page 3 of 13

TABLE OF CONTENTS

Section

Publication Record ..............................................................................................................................

Page

2

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

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

3.2 Required Medical X-Rays ...........................................................................................................5

3.3 Equipment and Techniques ........................................................................................................6

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

3.4.1 Basis and Methodology ......................................................................................................7

3.4.2 Fisher Machine...................................................................................................................8

3.4.3 Xonics System ...................................................................................................................9

3.4.4 Bennett System..................................................................................................................9

3.5 Uncertainty................................................................................................................................10

3.6 Dose Reconstruction.................................................................................................................10

References ........................................................................................................................................11

Glossary ............................................................................................................................................13

LIST OF TABLES

Table

3-1 LLNL X-ray equipment...............................................................................................................

Page

6

3-2 Analogues for IREP organs not included in ICRP Publication 34............................................... 8

3-3 Organ dose equivalents (rem) at different times for 14- × 17-in. PA chest 

radiography ...............................................................................................................................9
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ACRONYMS AND ABBREVIATIONS

cm centimeter

DCF dose conversion factor

DOE U.S. Department of Energy

ESE entrance skin exposure

FDA Food and Drug Administration

Gy gray

ICRP International Commission on Radiological Protection

in. inch

IREP Interactive RadioEpidemiological Program

keV kiloelectron-volt (1,000 electron volts)

kVp kilovolts-peak

LLNL Lawrence Livermore National Laboratory

mA milliampere

mm millimeter

mR milliroentgen

mrad millirad

NCRP National Council on Radiation Protection and Measurements

PA posterior-anterior

R roentgen

s second

SID source-to-image distance

SSD source-to-skin distance

U.S.C. United States Code
Document No. ORAUT-TKBS-0035-3 Revision No. 00 Effective Date: 08/22/2005 Page 5 of 13

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 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 Employees 

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

Since beginning in 1952, chest X-ray examinations have been prescribed by Health Services 

Department clinicians at Lawrence Livermore National Laboratory (LLNL). In addition to exposure of 

the lungs, other tissues of the body are irradiated by the primary X-ray beam and by scattered and 

leakage photons. This document develops claimant-favorable estimates of doses from occupational 

medical X-rays to the lungs and other organs of the body. These doses, determined for chest 

examinations during different periods at LLNL, are based on the operating parameters of the 

machines and the conditions of exposure, insofar as these are known.

3.2 REQUIRED MEDICAL X-RAYS

Existing documents do not furnish a complete record of the specific criteria used since 1952 to 

determine either which workers were required to have X-ray examinations or the frequencies of the 

examinations. This summary is based on record searches and discussions with present and former 

staff members of the Health Services Department of LLNL. 

From 1952 until about 1993, baseline X-rays were required for all pre-employment evaluations. In 

August of 1990, a Food and Drug Administration (FDA) survey of the medical X-ray program at LLNL 

provided the following recommendation: “Chest radiographs were indicated to be routinely performed 

as a requirement for employment at the facility. Documentation should present the reasons for this 

routine procedure. Chest radiographs are apparently not done as a routine part of regular or periodic 

examinations” (Van Pelt 1990).

LLNL Health Services Department Radiography Program, March 1991, provides the following 

information (LLNL 1991): 

Requisition of X-ray studies for the purpose of diagnostic information should be based 

on clinical evaluation. Diagnostic X-ray examinations will be requested after an 

appropriate medical history and physical examination has been performed, in 

accordance with reasonable medical practice and occupational guidelines. Diagnostic 

objective, relevant medical history and X-ray procedure requested will be recorded on 

the radiographic request form. ... Based on the unique nature of the work performed at 

LLNL, a pre-employment baseline PA [posterior–anterior] chest X-ray examination is 

required. This film may be done at the time of pre-employment examination or a copy of 

a previous film or report may be requested and kept on file. Medical surveillance 

programs may mandate periodic chest X-rays. Periodic chest X-ray examinations 

unrelated to job exposure will not be done routinely but may be ordered by the examiner 

if clinically indicated. 
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Detailed records were made for all X-ray examinations. The records include identification of the 

individual, the type of examination, data on operating parameters for the procedure, and other 

pertinent information. It appears that a single PA chest projection was standard practice. 

Radiographs are archived at LLNL and can be consulted. There is no evidence that fluoroscopy was 

ever used at LLNL for required medical examinations. A random sample of X-ray portfolios was 

selected from the archives and examined for seven individuals employed at LLNL in the 1950s and 

1960s. No small-format films were found.

Apart from the pre-employment baseline PA chest X-ray, it does not appear that LLNL mandated 

routine examinations on a regular basis for employees. Chest films for beryllium and asbestos 

workers were apparently introduced in the 1980s with a frequency dependent on the age and 

exposure of the individual (Noonan 2002). Available documents indicate that chest X-rays were 

administered on an individual basis in keeping with acceptable guidelines of occupational medicine. 

In the absence of a general policy for frequencies of regularly required chest X-rays, it is not feasible 

to address the three general dose reconstruction approaches (maximizing, best estimate, and 

minimizing) specified in Occupational X-Ray Dose Reconstruction for DOE Sites (ORAUT 2004). 

Dose reconstructors must consult an employee’s medical records to determine the extent of the 

worker’s required medical X-rays. 

3.3 EQUIPMENT AND TECHNIQUES

Table 3-1 lists the diagnostic medical X-ray units used at LLNL, as well as can be determined from 

existing records. Reported data were found and are included for entrance skin exposures (ESE) for 

PA chest examinations with all three systems. The earliest document (Graham and Williams 1975) 

describes results of an in-house radiation survey of the Fisher X-ray machine in the Medical 

Department by the LLNL Health Physics Group. Measurements gave an ESE of 19 mR [at a 

source-to-skin distance (SSD) of 157 cm], for a “typical” chest radiograph (100 kVp, 100 mA, 1/20 s). 

Beam collimation was deemed “satisfactory,” although the position of the light spot used for centering 

needed correction. The results of the survey indicated that the facility was operating properly and had 

adequate shielding. No other information was found about other aspects of the facility, such as 

screens, grids, film types, and development parameters. 

Table 3-1. LLNL X-ray equipment. 

Period Equipment and nominal operating parameters

1952–Dec. 1980 Fisher X-ray machine: 100 kVp, 100 mA, 1/20 s, normal filtration (3 mm Al), 

effective energy 32 keV, “satisfactory” collimation, measured ESE = 19 mR at 

SSD = 157 cm (Graham and Williams 1975)

Jan. 1981–Oct. 1990 Xonics: Stationary general purpose X-ray system, phototiming, Kodak M-35 film 

processor using Kodak XRP chemistry, blue-light sensitive film, measured ESE = 

45 mR (Van Pelt 1990)

Nov. 1990–Sept. 1992 Upgraded Xonics system: Blue-light sensitive film replaced with green-light 

sensitive Kodak T-MAT G and T-MAT L films, new cassette holders with 

compatible emitting screens, manual control techniques applied, measured ESE = 

11 to 15 mR (Winstanley 1990a,b; Noonan 1991; Thomas 1991)

Oct. 1992–present Bennett: Stationary general purpose radiographic system, Kodak M35A X-OMAT 

film processor, Lanex Regular screens, ESE = 12 mR (Thomas 1993) to 14 mR 

(Miles 1999); also 110 kVp, 200 mA, 0.017 s, ESE = 14 mR (LLNL 2004)

The Fisher system was replaced by a Xonics general purpose radiographic unit some time around 

1980, although it is not clear precisely when. The only survey report found for the Fisher unit (Myers 

and Williams 1979) compares design features with those recommended by the National Council on 

Radiation Protection and Measurements (NCRP) and by the State of California. The earliest 
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document found that pertains to the Xonics unit is a letter dated July 9, 1985 (Shingleton 1985). 

Therefore, the replacement of the Fisher by the Xonics machine must have occurred between these 

last two dates. A later report (Thomas 1991) on an FDA survey at LLNL on August 28 and 29, 1991, 

parenthetically mentions that the Xonics system control/generator was manufactured in 1980. 

Therefore, based on these dates, the organ doses given in this document for the period from 1952 

through December 1980 are for the Fisher machine and those for January 1981 through September

1992 are for the Xonics machine.

In the 1980s, a formal interagency agreement between the U.S. Department of Energy (DOE) and the 

FDA was established to conduct periodic surveys of government-owned, contractor-operated 

diagnostic X-ray equipment (Davis 1987). The surveys at LLNL were conducted by FDA. They 

covered the physical equipment itself as well as operational and administrative procedures. A series 

of specific recommendations was made by FDA following their survey on August 15, 1990 (Van Pelt 

1990). A principal objective, among others, was to reduce the ESE for a chest radiograph from the 

measured value of 45 mR. A number of modifications were made to the Xonics system to upgrade 

the technique for chest X-rays, as summarized in the third row of Table 3-1. The ESE was reduced to 

the range of 11 to 15 mR (Winstanley 1990b, Thomas 1991). With the alterations, the estimated 

organ doses for examinations with the Xonic machine were substantially reduced to lower values as 

of November 1990 (Noonan 1991).

The Bennett X-ray machine was installed at LLNL in September 1992 (Higginson 1992), replacing the 

Xonics unit, and it is still in use today. The new system underwent a complete, in-depth survey by 

FDA on October 27, 1992 (Thomas 1993). All items tested were within federal specifications. The 

estimated ESE with automatic exposure control was reported as 12.15 mR for a PA chest exam. 

Over time, values of ESE in the range 12 to 14 mR were reported (Table 3-1).

Quality assurance has been verified regularly by in-house surveys and by FDA visits. The 

interagency agreement between DOE and FDA was concluded around the end of the 1990s. Since 

then LLNL has continued to have annual outside reviews performed under contract.

Repeat or retake studies have been conducted. There is no indication of any significant repeat rate.

3.4 ORGAN DOSE CALCULATIONS

3.4.1

With the exception of that for the skin, estimations of the mean dose equivalents to individual organs 

of the body from a given X-ray exposure are based on dose conversion factors (DCFs) provided in 

Publication 34 of the International Commission on Radiological Protection (ICRP 1982). Skin doses 

are obtained by using backscatter factors from Table B.8 of NCRP (1989). Tables of DCFs are given 

in ICRP (1982) for seven organs in an adult anthropomorphic phantom for a number of common 

radiographic examinations with beams of different quality. For the PA chest projection, a 

source-to-image distance (SID) of 183 cm (72 in.) and an image receptor size of 35.6 × 43.2 cm (14 × 

17 in.) are used. For an organ not included in ICRP (1982), but needed for the Interactive 

RadioEpidemiological Program (IREP), the DCF is taken to be that for the anatomically closest organ 

in the ICRP tables. Table 3-2 lists the ICRP reference organs for the IREP analogues (ORAUT 2003). 

When the reference organ is the lung, different values of the organ doses are given in ICRP (1982) for 

males and females. The larger of the two values is assigned for the dose equivalent to the IREP 

organ analogue.

Basis and Methodology
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Table 3-2. Analogues for IREP organs not included in ICRP 

Publication 34 (ICRP 1982).

Anatomical

location

ICRP Publication 34

reference organ

IREP

organ analogue

Thorax Lung Bone surfaces

Esophagus

Liver/gall bladder/spleen

Remainder organs

Stomach

Thymus

Abdomen Ovaries Colon/rectum

Urinary/bladder

Head and neck Thyroid Eye/brain

The ICRP tables were developed under the assumption that the primary X-ray beam is collimated to 

the image receptor size. The application of these DCF tables to the early X-ray machines, particularly 

before about 1970, must therefore be made in a way that compensates for the lack of collimation. 

Claimant-favorable allowance for this circumstance during different periods in the past, based on 

ICRP (1982), has been assessed in the generic document by ORAUT (2003), which will be applied to 

estimate doses from the Fisher machine. In addition, when other data are not available, ORAUT 

(2003) recommends that the following values be used to express beam quality in terms of the halfvalue layer of Al: 2.5 mm prior to 1980 and 4.0 mm for subsequent years. The ICRP (1982) values 

are used directly to obtain the organ doses for examinations with the Xonics and Bennett systems in 

Table 3-1.

The ICRP DCFs are provided for an SID of 183 cm (72 in.) and an image-receptor size of 35.6 × 

43.2 cm (14 × 17 in.). Allowing 5 cm for a cassette thickness and 26 cm for the average chest 

thickness for a PA view implies an SSD of 152 cm (60 in.). Of the seven organs in ICRP (1982), 

separate doses for males and females are given for the active bone marrow and the lungs.

The ICRP DCFs give the average dose equivalent in a given organ in milligray for different beam 

qualities when the entrance kerma (air kerma in air without backscatter) is 1-Gy. In what follows, the 

approximation will be made that an ESE of 1 R produces a skin entrance kerma of 1 rad (ORAUT

2003). In addition to simplifying the computations, this assumption is well within relatively large 

uncertainties from other sources and is claimant-favorable. 

Table 3-3 lists the resultant organ dose equivalents for the periods during which each X-ray system 

was in use. The following sections discuss each system. 

3.4.2

No information about the Fisher X-ray system prior to the 1975 survey by Graham and Williams was 

found. Their survey reported a measured ESE of 19 mR with an SSD of 157 cm. For the smaller 

value used in the present document (SSD of 152 cm), the ESE is 19 mR × (157/152)2 = 20 mR = 

0.020 R. The skin entrance kerma is thus 0.020 rad. In the absence of earlier documentation, the 

pre-1970 default values for organ doses given in Table 3-3 for the period 1952 through December

1969 are taken from Table 4.0-1 of ORAUT (2003). For January 1970 through December 1980, when 

the Fisher machine was probably retired, the doses in Table 3-3 are based on the default values from 

ORAUT (2003) for this time period and scaled to be consistent with the 1975 measurements of 

Graham and Williams. Since the latter work showed the entrance kerma to be 0.020 rad and the 

default value is 0.10 rad for this time period, the doses given in column three of Table 3-3 are scaled 

to one-fifth their respective values in Table 4.0-1 of ORAUT (2003).

Fisher Machine
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Table 3-3. Organ dose equivalents (rem) at different times for 14- × 17-in. PA chest radiography. 

Organ

Dose equivalent (rem)

1952-Dec 1969

Fisher

ESE=0.20 R

Jan 1970-Dec 1980

Fisher

ESE = 0.020 R

Jan 1981-Oct 1990

Xonics

ESE = 0.045 R 

Nov 1990-Sep 1992

Xonics

ESE = 0.015 R 

Oct 1992-present

Bennett

ESE = 0.014 R

Bone marrow 

(active)

Male 1.8E-2 

Female 1.7E-2

Male 1.8E-3 

Female 1.7E-3

Male 8.0E-3 

Female 7.7E-3

Male 2.7E-3 

Female 2.6 E-3

Male 2.5E-3 

Female 2.4E-3

Bone surfaces 9.0E-2 9.0E-3 3.0E-2 1.0E-2 9.4E-3

Breast (female) 9.8E-3 9.8E-4 5.2E-3 1.7E-3 1.6E-3

Colon/rectum 2.5E-2 2.0E-5 2.3E-4 7.8E-5 7.3E-5

Esophagus 9.0E-2 9.0E-3 3.0E-2 1.0E-2 9.4E-3

Eye/brain 6.4E-3 6.4E-4 3.5E-3 1.2E-3 1.1E-3

Liver/gall 

bladder/spleen

9.0E-2 9.0E-3 3.0E-2 1.0E-2 9.4E-3

Lungs Male 8.4E-2

Female 9.0E-2

Male 8.4E-3

Female 9.0E-3

Male 2.8E-2

Female 3.0E-2

Male 9.4E-3

Female 1.0E-2

Male 8.8E-3

Female 9.4E-3

Ovaries 2.5E-2 2.0E-5 2.3E-4 7.8E-5 7.3E-5

Remainder 9.0E-2 9.0E-3 3.0E-2 1.0E-2 9.4E-3

Stomach 9.0E-2 9.0E-3 3.0E-2 1.0E-2 9.4E-3

Testes 5.0E-3 2.0E-7 4.5E-7 1.5E-7 1.4E-7

Thymus 9.0E-2 9.0E-3 3.0E-2 1.0E-2 9.4E-3

Thyroid 3.5E-2 6.4E-4 3.5E-3 1.2E-3 1.1E-3

Urinary/bladder 2.5E-2 2.0E-5 2.3E-4 7.8E-5 7.3E-5

Uterus (embryo) 2.5E-2 2.6E-5 2.3E-4 7.8E-5 7.3E-5

Skin 2.7E-1 2.7E-2 6.3E-2 2.1E-2 2.0E-2

3.4.3

The Xonics system replaced the Fisher unit around January 1981, and it operated through about 

September 1992. Although there is somewhat more information available for it than for the Fisher 

system, the number of documents is limited. However, reports from an FDA survey on August 15, 

1990 (Van Pelt 1990), and from the follow-up by LLNL (Noonan 1991) provide considerable detailed 

information. The survey tested an array of items and resulted in a number of suggested action items. 

One concern was the finding that the ESE measured with a phantom for chest X-rays was 45 mR. 

Subsequent improvements upgraded the Xonics system in a number of ways, as noted in Table 3-1. 

The ESE was reduced to a reported range of 11 mR to 15 mR (Winstanley 1990a,b), which was 

verified by the FDA survey of the following year (Thomas 1991).

Xonics System

No measurements were located that document the ESE for the Xonics chest exams at earlier times, 

from its beginning in January 1981 until the August 15, 1990, survey. In the absence of data to the 

contrary, the claimant-favorable assumption is made that the ESE was 0.045 R and the skin entrance 

kerma was 0.045 rad for the entire second period in Table 3-1. Thereafter, from November 1990 until 

its replacement after September 1992, the ESE is assumed to be 0.015 R and the entrance kerma, 

0.015 rad. No records were found in which this level was exceeded. Table 3-3 lists the organ doses 

using these two values for the kerma and ICRP (1982).

3.4.4

The FDA performed a survey of the Bennett X Ray Company system on October 27, 1992 (Thomas 

1993). A large number of items were checked, and all were verified to be within federal specifications. 

Under automatic exposure control, the ESE was reported to be 12.15 mR for a PA chest X-ray. 

Records show that the Bennett system has operated satisfactorily. An FDA survey on September 9, 

1999, measured an ESE of 14 mR for PA chest exposures with a phantom (Miles 1999). The ESE 

value of 0.014 R, which was also determined recently (LLNL 2004), was assumed for the Bennett 

Bennett System
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system, which operated from October 1992 to the present. Table 3-3 lists the resultant organ doses 

with the entrance kerma of 0.014 rad.

3.5 UNCERTAINTY

Uncertainties in the required occupational medical X-ray organ doses have been analyzed in ORAUT

(2003). The document considers several major sources of uncertainty: measurement errors; 

variations in applied voltage (peak voltage), beam current, and exposure time; and uncertainties due 

to patient size and placement. ORAUT (2003) assesses the relative error in an individual ESE or 

organ dose to be ±30% at 1 standard deviation. For claimant-favorable adjustment, it is estimated 

that the actual doses could have been up to 30% larger than those given in Table 3-3. 

3.6 DOSE RECONSTRUCTION

Table 3-3 lists the claimant-favorable best estimates of the organ dose equivalents for a PA chest 

X-ray. The uncertainty analysis indicates that actual doses would not likely exceed 1.3 times those 

values in individual cases.
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REFERENCES

Davis, J. T., 1987, “Health Physics Survey Program of Government-Owned Contractor-Operated 

(GOCO) Medical Diagnostic X Ray Equipment,” letter to Robert O. Godwin (Lawrence 

Livermore National Laboratory), February 25, U.S. Department of Energy, San Francisco 

Operations Office, San Francisco, California. 

Graham, C. L., and G. E. Williams, 1975, “Radiation Survey of the X-Ray Unit at Building 310”, 

interdepartmental letter to Dr. J. O. Beatty, April 1, Lawrence Livermore National Laboratory, 

Livermore, California. 

Higginson, J., 1992, Report of Assembly of a Diagnostic X-Ray System, Lawrence Livermore National 

Laboratory, Livermore, California, September 17. 

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

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

LLNL (Lawrence Livermore National Laboratory), 2004, [radiological data sheets], Health Services, 

Livermore, California, June 25.

LLNL (Lawrence Livermore National Laboratory), 1991, LLNL Health Sciences Department 

Radiography Program, March 1991, Livermore, California. 

Miles, K., 1999, [radiation survey of LLNL medical X-ray facility], FDA letter to K. Noonan, October 18, 

Lawrence Livermore National Laboratory, Livermore, California. 

Myers, D., and G. Williams, 1979, “Review of Medical X-Ray Unit in Building 310”, interdepartmental 

letter to George Liu, March 9, Lawrence Livermore National Laboratory, Livermore, California. 

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. 

Noonan, K., 1991, untitled letter to W. F. Van Pelt (FDA), January 10, Lawrence Livermore National 

Laboratory, Livermore, California. 

Noonan, K., 2002, “NIOSH Request for Description of X-ray Protocols,” cover memorandum, May 17, 

Lawrence Livermore National Laboratory, Livermore, California. 

ORAUT (Oak Ridge Associated Universities Team), 2003, Dose Reconstruction from Occupationally 

Related Diagnostic X-Ray Procedures, ORAUT-OTIB-0006, Rev. 02, Oak Ridge, Tennessee, 

December 29.

ORAUT (Oak Ridge Associated Universities Team), 2004, Occupational X-Ray Dose Reconstruction 

for DOE Sites, ORAUT-PROC-0061, Rev. 00, Oak Ridge, Tennessee, December 1.

Shingleton, Kathleen L., 1985, “Calibration of OHS X-Ray Machine,” interdepartmental letter to G. Liu, 

July 9, Lawrence Livermore National Laboratory, Livermore, California. 
Document No. ORAUT-TKBS-0035-3 Revision No. 00 Effective Date: 08/22/2005 Page 12 of 13

Thomas, M., 1991, “Results of FDA Diagnostic X-Ray Survey," FDA memorandum to J. H. Spickard 

(Medical Director, Health Sciences Department), September 20, Lawrence Livermore National 

Laboratory, Livermore, California. 

Thomas, M., 1993, “Results of FDA Diagnostic X-Ray Survey,” FDA memorandum to Dr. J. Spickard

(Medical Director), LLNL, January 20, Lawrence Livermore National Laboratory, Livermore, 

California. 

Van Pelt, W. F., 1990, FDA letter to Dr. J. H. Spickard (Medical Director, Health Sciences 

Department), August 29, Lawrence Livermore National Laboratory, Livermore, California. 

Winstanley, Jim, 1990a, “LLNL Medical X-Ray Unit”, internal memorandum to G. Mansfield, August 

21, Lawrence Livermore National Laboratory, Livermore, California. 

Winstanley, J. L., 1990b, “Medical X-Ray Exposure Evaluation”, interdepartmental letter to Dr. J. 

Spickard (Medical Director, Health Sciences Department), October 18, Lawrence Livermore 

National Laboratory, Livermore, California. 
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GLOSSARY

absorbed dose

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

backscatter

Radiation that is scattered backwards, enhancing skin dose in areas where X-ray beam enters 

the body.

dose equivalent

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

dose in rad, unit is rem.

exposure

Amount of electric charge produced per unit mass of air by electromagnetic radiation.

gray (Gy)

Unit of absorbed dose, defined as 1 joule per kilogram. It is equal to 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 gray. The word derives from kinetic 

energy released per unit mass. 

primary X-rays 

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

rad

Unit of absorbed dose, defined as 100 ergs per gram. It is equal to is 0.01 Gy. 

rem

Unit of dose equivalent. 

roentgen

Unit of exposure.

secondary X-rays 

As distinct from primary X-rays, secondary X-rays are those that are scattered from objects or 

leak from the source assembly.

X-ray

(1) Electromagnetic radiation emitted by fast electrons slowing down in matter or in certain 

electronic transitions in atoms. (2) A radiograph produced by X-rays.