This study compares organ doses, effective doses, and cancer risk in thyroid cancer patients treated with either a single 3700 MBq (100 mCi) or three times of 1110 MBq (30 mCi) ) I-131 doses 15 days apart. Nineteen patients (16 females, 3 males) underwent whole-body scans at 24 and 48 hours post-administration after one month using 37 MBq of I-131. Organ dosimetry was calculated with OLINDA/EXM and cancer risks estimated using ICRP 103. Fractionation lowered organ doses and cancer risk by ~10% in both sexes. Females patients’ consistently experienced higher absorbed doses and risks. The lungs and bladder wall were the largest contributors to overall risk.. Fractionated I-131 therapy modestly reduces exposure and supports sex-specific planning.
