Radiation safety considerations for post-iodine-131 thyroid cancer therapy

The purpose of this study was to develop guidelines based on direct patient measurements as to when 131I-treated thyroid cancer patients may resume close personal contact after release from the hospital. External exposure rates were measured on 27 patients using a calibrated ionization survey meter. The patients' exposure rates were measured at the time of release from the hospital and 2-7 days post-hospital discharge. Measurements were taken at 1, 0.6 and 0.3 meters from the patient's upright body axis (stomach to thyroid). Vertical movement of the survey instrument was utilized to obtain the maximum reading each time. All patients had exposure rates less than 2 mR/hr at 1 meter at 2-4 days post-hospital discharge. Eight-eight percent (21/24) had exposure rates less than 2 mR/hr at 0.6 meter at 2-4 days post-hospital discharge. Guidelines can be prepared specifically for thyroid cancer therapy patients that are rational and consistent with existing radiologic health standards.