Radiation exposure to allied health personnel handling blood specimens from patients receiving radioactive iodine-131 and recombinant human TSH (thyrogen®) stimulation

Abstract

Background With increasing use of rhTSH stimulation protocol in I-131 treatment of thyroidectomized DTC, there is increasing concern regarding radiation safety during collection and processing of radioactive blood samples. Our study aims to quantify this radiation exposure in the context of current radiation guidelines to provide a practical safety framework. Materials and Methods We analysed 45 patients prospectively referred to a tertiary center in Singapore, who had histologically proven DTC, and who were thyroidectomised and planned for I-131 with rhTSH stimulation. Each patient received rhTSH for 2 consecutive days, with I-131 administered 24 hours after, and stimulated Tg blood sample collected and processed 72 hours after the last rhTSH dose. We measured radiation exposures with dosimeters. Based on the average and maximum exposure rates calculated, we extrapolated and derived the number of radioactive blood samples that could be safely collected and processed. Results Mean hand and body radiation exposures during venepuncture and blood processing were generally significantly higher than background radiation. Based on average exposure rates, the permissible number of blood samples that can be collected and processed is 9.09 x 103 per year (24 per day) and 8.70 x 104 per year (238 per day) respectively. Conclusions This is the first study to date to extrapolate permissible thresholds that can serve as a practical guideline to the number of radioactive blood samples that can be safely collected and processed, following radioactive iodine therapy, within the limits of current radiation guidelines. Once validated, generalizations to other radioactive therapies may be considered. Keywords: Iodine-131, radiation safety, Thyrogen stimulation, differentiated thyroid carcinoma, laboratory specimens