Exposure and contamination assessment of nuclear medical staff during radioiodine therapy for thyroid cancer

To assess exposure and contamination induced by patients treated with iodine-131 on nuclear medical staff, we performed several measurements during patient hospitalization: the dose rate, skin contamination, and room air and ground contamination. These measurements were performed for 12 patients treated with 3.7 GBq of iodine131, 6 stimulated by TSHr and 6 by thyroid hormone withdrawal. Maximum values were measured 4 h after iodine administration, with a mean dose rate of 133 mu Sv h(-1) at 1 meter, a mean activity concentration of 8.8 MBq g(-1) in saliva, a mean room air concentration of 183 Bq m(-3) and a ground concentration below 0.5 Bq cm(-2). These results highlight a wide inter-patient variability, resulting from individual physiological differences in iodine elimination and from various applications of hygiene instructions. Room air contamination has a small impact in terms of staff exposure, compared with external exposure from the patient. Nevertheless, it is probably the main origin of internal contamination of nuclear medical staff. It is now recommended for the staff to limit visits in the room in the first 24 h, and for all patients to strictly follow hygiene instructions.