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Title: Age- and sex-specific estimation of dose to a normal thyroid from clinical administration of iodine-131

This report describes the derivation of an age- and sex-dependent model of radioiodine dosimetry in the thyroid and the application of the model to estimating the thyroid dose for each of 4215 patients who were exposed to /sup 131/I in diagnostic and therapeutic procedures. In most cases, the data available consisted of the patient's age at the time of administration, the patient's sex, the quantity of activity administered, the clinically determined uptake of radioiodine by the thyroid, and the time after administration at which the uptake was determined. The model was made to conform to these data requirements by the use of age-specific estimates of the biological half-time of iodine in the thyroid and an age- and sex-dependent representation of the mass of the thyroid. Also, it was assumed that the thyroid burden was maximum at 24 hours after administration (the /sup 131/I dose is not critically sensitive to this assumption). The metabolic model is of the form A(t) = K x (exp(-..mu../sub 1/t) - exp(-..mu../sub 2/t)) ..mu..Ci where ..mu../sub i/ = lambda/sub r/ + lambda/sub i//sup b/ (i = 1, 2), lambda/sub r/ is the radiological decay-rate coefficient, and the lambda/sub i//sup b/ are biological removal-rate coefficients. The valuesmore » of lambda/sub i//sup b/ are determined by solving a nonlinear equation that depends on assumptions about the time of maximum uptake and the eventual biological loss rate (through which age dependence enters). An addendum (Appendix C) extends the method to other radioiodines and gives age- and sex-dependent dose conversion factors for most isotopes.« less
Authors:
;
Publication Date:
OSTI Identifier:
7145482
Report Number(s):
NUREG/CR-3955; ORNL/TM-9800
ON: TI86015368
DOE Contract Number:
AC05-84OR21400
Resource Type:
Technical Report
Research Org:
Oak Ridge National Lab., TN (USA). Health and Safety Research Div.
Country of Publication:
United States
Language:
English
Subject:
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.; 62 RADIOLOGY AND NUCLEAR MEDICINE; THYROID; PERSONNEL DOSIMETRY; AGE DEPENDENCE; IODINE 131; MATHEMATICAL MODELS; PATIENTS; RADIATION DOSES; SEX DEPENDENCE; BETA DECAY RADIOISOTOPES; BETA-MINUS DECAY RADIOISOTOPES; BODY; DAYS LIVING RADIOISOTOPES; DOSES; DOSIMETRY; ENDOCRINE GLANDS; GLANDS; INTERMEDIATE MASS NUCLEI; IODINE ISOTOPES; ISOTOPES; NUCLEI; ODD-EVEN NUCLEI; ORGANS; RADIOISOTOPES 560161* -- Radionuclide Effects, Kinetics, & Toxicology-- Man; 550601 -- Medicine-- Unsealed Radionuclides in Diagnostics; 550604 -- Medicine-- Unsealed Radionuclides in Therapy-- (1980-)