dosimetry for epidemiological studies: learning from the past, looking to the future

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    Dosimetry for Epidemiological Studies: Learning from the Past, Looking to theFutureAuthor(s): Steven L. Simon, Andr Bouville, Ruth Kleinerman, and Elaine RonSource: Radiation Research, 166(1):313-318. 2006.Published By: Radiation Research SocietyDOI: http://dx.doi.org/10.1667/RR3536.1URL: http://www.bioone.org/doi/full/10.1667/RR3536.1

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    RADIATION RESEARCH 166, 313318 (2006)0033-7587/06 $15.00q 2006 by Radiation Research Society.All rights of reproduction in any form reserved.

    SUMMARY

    Dosimetry for Epidemiological Studies: Learning from the Past,Looking to the Future

    Steven L. Simon,1 Andre Bouville, Ruth Kleinerman and Elaine Ron

    Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Bethesda, Maryland

    INTRODUCTION

    Assembling the suite of manuscripts for this special issueof Radiation Research has afforded us a unique opportunityto evaluate the various methods of dosimetry used in sup-port of epidemiological studies as well as the strengths andweaknesses of different dosimetric approaches. Of equalimportance is having the opportunity to highlight elementsof dosimetry that are especially important to conductingconvincing epidemiological studies.

    In general, analytical epidemiological studies of radiationeffects attempt to combine information on disease (e.g. can-cer) occurrence with estimates of radiation dose to individ-uals such that the relationship between the increase in dis-ease incidence compared to the background rate as a func-tion of the true dose can be described. With regard to thelanguage and science of dosimetry, there are a number ofterms, assumptions and implied meanings that are often notclear to the variety of scientists involved in radiation epi-demiology studies. This issue should help inform these re-searchers.

    In this special issue of Radiation Research devoted tothe dosimetric aspects of radiation epidemiology, we at-tempted to clarify what is meant by dosimetry for epi-demiological studies, what is required to ensure that thefindings of dosimetry-based epidemiological studies are ascredible and generalizable as possible, and to give practicalexamples from current or recent studies. While this collec-tion of papers certainly does not cover all of the aspects ofdosimetry in epidemiology, it is meant to describe wherewe have been in terms of applying dosimetry for epide-miological purposes and where we are going to further ad-vance the discipline.

    SUMMARY OF STUDIES PRESENTED

    Readers of this issue of Radiation Research are probablyalready acquainted with a wide range of dosimetric meth-

    1 Address for correspondence: Division of Cancer Epidemiology andGenetics, National Cancer Institute, 6120 Executive Blvd., Room 7100,Bethesda, MD 20892; e-mail: ssimon@mail.nih.gov.

    ods. Here we briefly summarize the principal identifyingcomponents of the ten applications of dosimetric methodsdescribed in the individual papers. Table 1 contains a listingof the papers and a greatly abbreviated description of themethods employed and the available input data.

    Medical Dosimetry

    Methods for estimation of organ doses after the admin-istration of radioisotopes as described by Brill et al. (1) arewell developed and have depended for several decades onthe formulations of the Medical Internal Radiation Dose(MIRD) Committee [see ref. (2) for a primer on those meth-ods]. The basis for dose estimation by these methods is ametabolic model coupled with a measured amount of ad-ministered radioactive material. Unlike occupational andenvironmental dose estimations, the great advantage inthese situations is that the amount of activity administeredis usually known. Though the ability to accurately measurethe administered activity does not pose any great technicalchallenges, differences between individuals in their metab-olism (kinetics) and anatomy (size and exact location oforgans) lead to uncertainties in the absorbed dose for anyidentified person. Thus, even when activity intake is known,doses cannot be estimated with absolute precision. One ofthe limitations in estimating individual dose arises from theuse of standardized or mathematical phantoms that are as-sumed to representing the individual receiving the treatmentdose.

    Even iodine-131, one of the most studied nuclides forwhich kinetics in the human body has been described sincethe early 1950s (3), has dose uncertainties, partly becauseof human variation, but also due to secular changes in thedietary component of stable iodine. Changes in iodine in-take have occurred at the local, national and internationallevels, and these can affect the amount of radioiodine ab-sorbed by each individual thyroid gland.

    Estimation of doses from medical procedures, includingtreatments and diagnostic procedures, as described by Sto-vall et al. (4), involves traditional treatment planning tech-niques, archival data collection, and contemporary mea-

  • 314 SUMMARY

    TABLE 1Summary of Physical or Calculation-Based Dosimetric Methods Described in Publications of this Issue

    Exposurecategory/authors

    Exposure setting, population,and location

    Organs/tissues fordose estimation

    Mode of exposure(internal, external)

    Primary methods andinput data

    Medical

    Brill et al. (1) Clinical: patients (emphasis onU.S.)

    Thyroid primarily Internal (131I) Metabolic model using measuredadministered radionuclides

    Stovall et al. (4) Clinical: patients (emphasis onU.S.)

    All organs 1 redbone marrow(RBM)

    External and internal Measurements and calculationsbased on records from admin-istered treatments and/or diag-nostic tests

    Occupational

    Bouville et al. (6) Reactor: clean-up workers(Ukraine)

    RBM primarily, in-ternal (minor)

    External primarily,internal (minor)

    Film badge measurements (indi-vidual or group), exposurerate, questionnaire responses

    Gilbert et al. (7) Various reactors: workers (U.S.,Europe)

    Whole-body External primarily Film badge and other dosimetermeasurements

    Simon et al. (8) Clinical: radiologic technolo-gists (U.S.)

    All organs, emphasison breast, skin,RBM

    External Film badge measurements, ques-tionnaire responses, historicalliterature

    Environmental

    Beck et al. (9) Public: population living down-wind of nuclear test sites(U.S., Kazakhstan, MarshallIslands)

    Thyroid primarily,also RBM

    External and internal Measurements of exposure ratecoupled with environmentaltransfer models, questionnaireresponses

    Cullings et al. (12) Public: A-bomb survivors (Hi-roshima and Nagasaki, Japan)

    Whole-body External Reconstruction of detonationconditions (source term), geo-graphic location, house con-struction

    Degteva et al. (11) Public: people living near con-taminated river (Chelyabinsk,Russia)

    All organs 1 RBM External and internal Release data and environmentaltransfer model

    Likhtarev et al. (10) Public: people living nearChernobyl reactor (Ukraine,Belarus)

    Thyroid External and internal Measurements of 131I in thyroidplus model

    Puskin et al. (15) Homes and mines (internation-al)

    Lung Internal by inhala-tion

    Physics based model to convertfrom exposure to dose, depen-dent on environmental mea-surements of 222Rn

    surements, sometimes of aged radiation-generating ma-chines. The goal of those various techniques is, in general,to characterize the dose to organs/tissues outside of treat-ment areas, primarily due to within-body scatter of radia-tion and leakage from the treatment machine. Various typesof phantoms are used for dose measurements and dose es-timation, including mathematical, anthropometric and waterphantoms. Therapy doses are particularly amenable to re-construction because, much like when radiopharmaceuticalsare administered, the irradiation conditions were controlledand the dose to the treatment site was recorded, althoughdetailed radiation records are not always accessible (5).Since patients comprise the largest population group ex-posed to doses ranging from very low to extremely high,dosimetry and risk associated with those exposures willcontinue to be a major focus of study.

    Occupational Dosimetry

    Occupational exposure includes a wide range of job de-scriptions in the medical, weapons construction, and nucle-

    ar power industries, and dosimetric methods reflect thosevarious conditions.

    Dose estimation for the Chernobyl clean-up workers asdescribed by Bouville et al. (6) took advantage of theunique exposure conditions that could be assumed as rela-tively homogeneous over the body. In that study, doseswere estimated by one of four different methods, dependingon the individual study subject and the da

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