LAUSR

Purpose Internal contamination may occur when unsealed radioactive substances are manipulated for radiopharmaceutical preparation. This work shows the results of internal contamination routine monitoring of workers in a Nuclear Medicine department manipulating Tc99m, I123, I131, In111, F18, Cr51, in a 12-months period. F18 dose preparation was performed through and automatic dose partitioner. Methods Every week and specifically on Friday morning, the most exposed workers to the risk of internal contamination, namely the technician (TEC) working in the hot-lab and the nuclear medicine physician (NMP) devoted to patient injection provided urine samples. Samples were measured for 3600″ with a NaI(Tl) scintillation detector, previously calibrated in efficiency. Minimum detectable activities (MDA) were: 1.0, 1.0, 1.7, 2.3, 3.6 and 13.7 Bq for Tc99m, I123, I131, In111, F18 and Cr51, respectively. The intake at the time of contamination was derived from the activity in the urine sample by using biological models in the hypothesis that the contamination happened two days before. The committed effective dose was evaluated by using ICRP coefficients for ingestion. The annual workload of manipulated activity was: 8462, 17, 22, 3, 9600 and 0.3 GBq of Tc99m, I123, I131, In111, F18 and Cr51, respectively. Results For the monitored period, the evaluated intakes were the following: 1.2 10 6 (1.1 10 6 ) Bq, 2.5 104 (1.5 10 3 ) Bq, 1.4 103 (1.2 10 3 ) Bq, 3.0 103 (0) Bq and 1.2 103 (2.3 10 2 ) Bq for TEC and (NMP) respectively, corresponding to committed effective doses of 25.3 (24.7) μSv, 5.2 (0.3) μSv, 31.5 (27.4) μSv, 0.9 ( Conclusions The routine monitoring of internal contamination shows that the committed effective dose to the workers in a Nuclear Medicine department in one year monitoring period is definitely lower than 1 mSv, showing that the working conditions are highly safe.