Development of a Simple Method for Determining the Absorbed Activity Concentration by the Thyroid Gland of Nuclear Medicine Staff

The occupational safety of nuclear medicine staff working with radioactive iodine (131I) has always been a major concern in nuclear medicine. Since 131I is a volatile substance, it may enter the body during respiration and be absorbed by the thyroid gland of the hospital staff, causing major health problems. This study aimed to develop a simple method for determining the activity concentration of absorbed 131I in the thyroid gland of nuclear medicine staff, using a home-made anthropomorphic neck-thyroid phantom. For this purpose, 131I, with an activity of 370 kBq, was injected inside the thyroid glands of the phantom. The dose rate was measured by placing a portable detector on the thyroid gland at the surface of the neck phantom. The measurements were repeated for two months. Next, a calibration curve was drawn for iodine activity inside the thyroid versus dose rate at the neck surface. The calibration curve was then used to estimate the absorbed activity in the thyroid of the staff in one of the main hospitals of Shiraz, Iran. Finally, a new software program was developed for assessing and recording the activity concentration of 131I accumulated in the thyroid gland. Every day, the dose rate was measured by placing the detector on the neck of the staff. The dose rates were converted to activity concentrations inside the thyroid, using the mentioned calibration curve. The results indicate that using the calibration factors for every detector, one can have the estimate of the radio-Iodine activity inside the thyroid. The method proposed in this study can be applied for internal contamination determination in normal working conditions and in accidents.