Analysis of pelvic 131I uptake after 131I whole body scan in patients with thyroid cancer

Objective To analyze and explore the possible mechanism for pelvic 131Ⅰ uptake after 131Ⅰ post treatment whole body scan (RX-WBS)in patients with differentiated thyroid cancer.Methods ①Data were retrospectively reviewed from 168 female patients with differentiated thyroid cancer(everyone has a RX-WBS).②46 patients were accepted by analyzing the characteristics of RxWBS and combing with some inclusion criteria,and then followed up.Results Among the 46 patients (46 positions accumulated 131Ⅰ)with significant pelvic 131Ⅰ uptake,6 patients had two reasons leading to pelvic 131Ⅰ uptake,and 2 patients had no specific reason.Among the 50 reasons for pelvic 131Ⅰ uptake,41 reasons related with uterus,3 reasons related to rectum,5 related to bladder and 1 related to ovarian chocolate cyst.Among the 41 reasons related to uterus,by combining the examinations of SPECT/CT,ultrasound,CT and the follow-up results,18 were uterine leiomyomas,9 were intrauterine devices,2 were endometrial thickening,3 were uterine cavity effusion,7 were menstrual periods,1 were uterine adenomyosis,1 were gestational sac.Conclusions (①In the Rx-WBS of female,the significant pelvic 131Ⅰ uptake is generally caused by uterus,but not bladder.And it usually means gynecological disease,especially uterine leiomyomas when excluding physiological factors.②It is generally easy to differentiate bladder from rectum because they have different characteristic features of the pelvic 131Ⅰ uptake.(③SPECT/CT plays a very important role in locating 131Ⅰ uptake in uterus. Key words: Thyroid neoplasms;  Iodine radioisotopes;  Whole body imaging;  Pelvic uptake