eR. ~ Op * © cons WM Va a 93 nent of Hyperthyroidism Table 6-1 Decay Characteristics of '?°I* Radiation Photons Energy (kev) Gamma 6.66 35.4 Kai X-ray 27.4 76.15 Kg, X-ray 30.9 20.56 Kyo x-ray 27.2 39.06 Keo X-ray 31.8 K int. conv. L int. conv. M int. conv. 3.6 30.9 34.6 80.0 11.42 1.9 KLL Auger KLX Auger 22.6 26.4 14.16 5.97 L x-rays Electrons N/100 Disintegrations KXY Auger LMN Auger MXY Auger 4.26 3.7 22.26 30.1 0.96 2.9 154.42 0.8 364.61 } A, = 0.0151 A; = 0.0107 _ A, = 0.0159 *Half-life: 60.2 days. result in more marked effects on the site of hormonogenesis than on the replicative capacity. Studies comparing the effects of "I and '*5] in animal systems have demonstrated recovery of function after initial suppression by '*I. A more marked effect was seen on iodine-concentrating mechanisms than on goitrogenesis,>***° and histopathological studies have confirmed the localization of dose.*® The cell survival studies of Greig et al.5’ are confirmatory. Only the work of Jongejan and Van Putten® indicates an opposite conclusion. They found no difference in the }*°I/*'I ratio for administered levels of activity to produceidentical Fig. 6-2. Schematic representation of percentage distribution of electron radiation dose inside thyroid cell. The radiations ema- nate from '*5] in the follicular colloid. (Reproduced with permission from Lewitus Z. et al., Seminars in Nucl. Med. /:411-421, 1972.) er 4X La ao SSO, lOw —————»| \ 4 effects on hormonal function and on cell killing. J ISOA 96% 4%