ASSESSMENT OF RADIATION SAFETY FROM VOLATILIZATION OF *'LIN THE TREATMENT OF HYPERTHYROIDISM AND THYROID CANCER

Abstract

Oral administration of ¹³¹l treatment doses to hyperthyroid and thyroid cancer patients is the most hazardous procedure in nuclear medicine due to possible volatilization of ¹³¹Iodine. Internal radiation exposure to medical personnel and patients involving the use of ¹³¹l were analysed and assessed at the Department of Radiology by air sampling method. The air sampling was performed on a daily basis in front of an iodine fume hood where treatment doses ranging from 18.5-740 MBq were openly given to 169 hyperthyroid patients during a period of 42 days. At Siriraj Hospital, two thyroid cancer patients are admitted together to the same room due to shortage of room. Room partition to control external radiation exposure is achieved by relocating two lead screens between the patients’ beds. To assess internal radiation exposure to the patients, concentration of ¹³¹I in air in the room was determined for two days during an isolation period in two pairs of treated patients. It was found that the daily concentration of ¹³¹I in air in front of the fume hood ranged from 0.9 to 262.7 Bq/m³, and the maximum concentration of I in air in the thyroid cancer patients’ room was 546.9 Bq/m³. All values were well below the established Derived Air Concentration (DAC) for I, 700 Bq/m³. It could be demonstrated that an individual intake of I in the thyroid gland would be less than the Annual Limit on Intake (ALI). It is concluded that where internal body burden of ¹³¹I is concerned, it is safe for medical personnel to openly administer treatment doses to hyperthyroid patients, and it is practically safe for two thyroid cancer patients to share the admitting room provided that sufficient shielding is established between their beds to control external radiation exposure.