NV/HEC Mtg. -Sept. 26-27, 1968 Page 5 LRL has been approached about the possibility of putting WASP data into a technique being developed by T. Crawford at LRL. Iv, MEDICAL IMPLICATIONS OF I-131 Col. J. C. Fitzpatrick, Field Command, medical aspect of radioiodine exposure, the human thyroid gland. DASA, briefed the Group on the particularly with respect to Although there are 24 isotopes of iodine, the important ones in fission production are I-131, I-132 and 1-135 because of their physical half-lives. is 8.05 days. The physical half-life of I-131 I-131 emits .608 mev beta which is the most important emission for thyroid injury. It penetrates three millimeters of tissue and is primarily responsible for cellular destruction of the thyroid. The biological half-life which depends upon the health of the patient, his state of nutrition, over 138 days. thyroid function, etce., varies from 60 days to Because the physical half-life is so short it becomes dominant and the effective half-life is about 7.6 days. In clinical medicine I-131 is the most commonly used iodine isotope. Diagnostic uses usually involve microcurie amounts from 5 to 15 microcuries. For therapy, doses are usually in the millicurie range, about 7 to 8 millicuries which amounts to a dose of I-13] per gram retained carcinoma, are about The highest doses, given to people with 150 millicuries total. pierre ee ew of 70 to 100 microcuries. An important factor in considering the hazard of I-131l is the fact that the uptake of 1-131 for children and for adults is approximately the QNL hy x YT TMs 17%