Microscopic energy absorption in the colloid of thyroid follicles from Auger electrons of iodine-125

In this study the microscopic energy absorption from Auger electrons of iodine-125 in colloid of two different thyroid models, which represent the normal and thyrotoxic thyroid glands, was theoretically calculated. Subsequently the range of highest energy Auger electrons of iodine-125 in thyroidal colloid was found to be about 72 μm. This range is considerably shorter than the radius of a normal thyroid follicle, about 150 μm, but is considerably longer than the 25 μm radius of a thyrotoxic thyroid follicle. On the other hand, the comparison of dose distributions in two different thyroid models showed that the similar activity of iodine-125 per gram of thyroid tissue is able to produce more radiotoxic effects on the thyrotoxic follicular cells. (author)