Abstract: Objective To investigate the development of nuclear medicine in Chongqing,determine the number of nuclear medicine radiation workers,and conduct internal radiation dose monitoring for radiation workers engaged in iodine-131（¹³¹I） therapy within the jurisdiction. Methods In 2021,the iodine measuring instrument for thyroid internal irradiation was used to monitor the thyroid ¹³¹I activity and thyroid organ dose of all iodine treatment workers in Chongqing. Based on the work situation of the monitored person,the annual accumulated effective dose was estimated. Results There were a total of 89 iodine treatment workers from 14 hospitals in Chongqing,of whom 36 had detected ¹³¹I in the thyroid gland,with a detection rate of 40.4%. The activity of ¹³¹I in the thyroid gland was 2.65-925.02 Bq,with an average activity of（85.66±176.93）Bq. The dose activity of thyroid organs to be accumulated was 0.18-62.11 μSv,with an average dose of（6.64±12.21）μSv. The annual effective dosage range was 0.01-3.11 mSv,with an average dose of （0.29±0.59）mSv. Logistic regression analysis showed that technician position was the risk factor for the annual accumulated effective dose（P<0.05）. Conclusions The detection rate of ¹³¹I in personnel and environment of some hospitals in Chongqing is relatively high,with 4 medical iodine treatment workers in the jurisdiction receiving an annual effective dose exceeding 1 mSv. Workplace and personal radiation protection should be strengthened to enhance radiation protection awareness among radiation workers.

Key words: Nuclear medicine, ¹³¹I, Internal radiation