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338. Results of routine monitoring of internal contamination of workers in a Nuclear Medicine department
Abstracts / Physica Medica 56 (2018) 133–278
positively evaluated RaySafe i2 in optimizing its way of working and provided useful suggestions on how to use the system. https://doi.org/10.1016/j.ejmp.2018.04.346
338. Results of routine monitoring of internal contamination of workers in a Nuclear Medicine department R. Matheoud a, B. Cannillo a, G.M. Sacchetti b, M. Brambila a a
AOU Maggiore della Carità, Medical Physics Department, Novara, Italy AOU Maggiore della Carità, Nuclear Medicine Department, Novara, Italy b
Purpose. Internal contamination may occur when unsealed radioactive substances are manipulated for radiopharmaceutical preparation. This work presents the result of routine monitoring of workers in a Nuclear Medicine department dealing with Tc99m, I123, I131, In111, F18, Cr51, in a 12-months period. F18 dose preparation is performed through and automatic dose partitioner. Methods. Every week, urine samples were collected from 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 patients injection. Samples were measured for 360000 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: 3.0, 17.0, 21.8, 0.3, 8462 GBq of Tc99m, I123, I131, In111, F18 and Cr51, respectively. Results. For the monitored period, the evaluated intakes were 1.2 106 (1.1 106) Bq, 2.5 104 (1.5 103) Bq, 1.4 103 (1.2 103) Bq, 3.0 103 (0) Bq and 1.2 103 (2.3 102) Bq for TEC and (NMP) respectively, and the committed effective doses of 25.3 (24.7) lSv, 5.2 (0.3) lSv, 31.5 (27.4) lSv, 0.9 (0) lSv and 0 (0) for Tc99m, I123, I131, In111 and Cr51, respectively. As expected, F18 activity in urine was below the MDA. Conclusions. The results of the routine monitoring of internal contamination shows that the committed effective dose to the workers in a Nuclear Medicine department is definitely lower than 1 mSv, showing highly safe working conditions. https://doi.org/10.1016/j.ejmp.2018.04.347
339. Radiometabolic treatment of hyperthyroidism after a patient specific dosimetric study: The radiation protection impact C. Canzi a,b, V. Longari b, M. Castellani b, M.F. Bardo b, A. D’Alessio c, R. Benti b a
Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, Medical Physics Dept, Milano, Italy b Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, Nuclear Medicine Dept, Milano, Italy c University of Milan, Medical Physics School, Milano, Italy Purpose. Hyperthyroidism is a diffuse disease mainly treated with I-NaI radiometabolic therapy. Recently published data report that in Europe at least 15.000/y treatments are performed. As hyperthyroidism is a benign condition, the optimization principle stated in art.56 of 2013/59/Euratom Council Directive should be strongly
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applied and radiometabolic treatment should be performed with the minimum activity necessary to reach the clinical purpose minimizing the exposure of non-target tissues. Aim of the work was to evaluate the radioprotection impact of 131I therapies for hyperthyroidism after patient-specific dosimetric-studies, with respect to a standard administration of 600 MBq (max activity allowed in Italy for outpatient treatments). Methods. 503 patients who solved hyperthyroidism within 1 year were considered (183 Graves, 383F, median age = 64y 17–89y]). Results. Median 131I administered activity was 385 MBq [66–629 MBq] and only 29% of the patients had the maximum allowed activity. Total administered activity was 209 GBq; if the standard activity of 600 MBq had been administered to all patients total would have been 302 GBq, 45% greater than the really used one. This acts on the patient mean effective dose and on the mean absorbed dose to the stomach wall (critical organ for 131I-NaI/ ICRP53) that were 5.8 Sv instead of 9.0 Sv and 177 mGy instead of 276 mGy respectively, with a maximum dose saving (9 times) for the patient who was given 66 MBq. The reduction of 131I administered activity also acts on the exposure of the nuclear medicine staff and of population: the mean dose rate at 1 m at the patient discharge time is 12 lSv/h instead of 20 lSv/h. This approach involves also the environment, as in the first 24 h 60% of administered activity is excreted. Conclusions. The application of a patient specific pretreatmentdosimetric study can reduce of 45% the radioprotection impact of 131 I treatments of hyperthyroidism with clinical results guaranteed and activity administered to the single patient can be decreased down to 9 times. https://doi.org/10.1016/j.ejmp.2018.04.348
340. Evaluation of worker inhaled activity after surface contamination C. Gori a, L. Fedeli a, R. Ropolo b a b
University of Florence, Dept. ‘‘Fisica e Astronomia”, Firenze, Italy A.O.U. Città della Salute e della Scienza di Torino, Torino, Italy
Purpose. The use of unsealed sources (either in nuclear medicine or in radiochemical bio-laboratories) involves the risk of internal contamination for workers after partial evaporation of the unsealed source during its use. This issue was already addressed in [1], the aim of this work is to extend that work towards a comprehensive model taking into account also the airborne contamination after radionuclide evaporation from the cumulated surface contamination of the working area. Methods. The above mentioned model takes into account the manipulation time (tm, the manipulated activity (A), the frequency of manipulations, the total time the workers spend in the laboratory (on an yearly basis), the air exchange ratio (R) and the half-life of the manipulated radionuclides. According to the actual working conditions, the model evaluates firstly the radionuclide air concentration as a function of time and thereafter the committed effective dose depending on the time spent in the laboratory by the worker. Results. During tm the radioisotope manipulation determines both air contamination (AC) and probabilistic surface contamination (SC). After tm AC decreases due to R, whereas surface contamination increases after each manipulation, decreasing only through physical decay, thus leading to an asymptotic SC in the long run. SC is more relevant for long-life radioisotopes. Conclusions. Application of the model to an actual bio-laboratory case shows that contribution to inhaled activity from surface con-
positively evaluated RaySafe i2 in optimizing its way of working and provided useful suggestions on how to use the system. https://doi.org/10.1016/j.ejmp.2018.04.346
338. Results of routine monitoring of internal contamination of workers in a Nuclear Medicine department R. Matheoud a, B. Cannillo a, G.M. Sacchetti b, M. Brambila a a
AOU Maggiore della Carità, Medical Physics Department, Novara, Italy AOU Maggiore della Carità, Nuclear Medicine Department, Novara, Italy b
Purpose. Internal contamination may occur when unsealed radioactive substances are manipulated for radiopharmaceutical preparation. This work presents the result of routine monitoring of workers in a Nuclear Medicine department dealing with Tc99m, I123, I131, In111, F18, Cr51, in a 12-months period. F18 dose preparation is performed through and automatic dose partitioner. Methods. Every week, urine samples were collected from 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 patients injection. Samples were measured for 360000 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: 3.0, 17.0, 21.8, 0.3, 8462 GBq of Tc99m, I123, I131, In111, F18 and Cr51, respectively. Results. For the monitored period, the evaluated intakes were 1.2 106 (1.1 106) Bq, 2.5 104 (1.5 103) Bq, 1.4 103 (1.2 103) Bq, 3.0 103 (0) Bq and 1.2 103 (2.3 102) Bq for TEC and (NMP) respectively, and the committed effective doses of 25.3 (24.7) lSv, 5.2 (0.3) lSv, 31.5 (27.4) lSv, 0.9 (0) lSv and 0 (0) for Tc99m, I123, I131, In111 and Cr51, respectively. As expected, F18 activity in urine was below the MDA. Conclusions. The results of the routine monitoring of internal contamination shows that the committed effective dose to the workers in a Nuclear Medicine department is definitely lower than 1 mSv, showing highly safe working conditions. https://doi.org/10.1016/j.ejmp.2018.04.347
339. Radiometabolic treatment of hyperthyroidism after a patient specific dosimetric study: The radiation protection impact C. Canzi a,b, V. Longari b, M. Castellani b, M.F. Bardo b, A. D’Alessio c, R. Benti b a
Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, Medical Physics Dept, Milano, Italy b Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, Nuclear Medicine Dept, Milano, Italy c University of Milan, Medical Physics School, Milano, Italy Purpose. Hyperthyroidism is a diffuse disease mainly treated with I-NaI radiometabolic therapy. Recently published data report that in Europe at least 15.000/y treatments are performed. As hyperthyroidism is a benign condition, the optimization principle stated in art.56 of 2013/59/Euratom Council Directive should be strongly
131
267
applied and radiometabolic treatment should be performed with the minimum activity necessary to reach the clinical purpose minimizing the exposure of non-target tissues. Aim of the work was to evaluate the radioprotection impact of 131I therapies for hyperthyroidism after patient-specific dosimetric-studies, with respect to a standard administration of 600 MBq (max activity allowed in Italy for outpatient treatments). Methods. 503 patients who solved hyperthyroidism within 1 year were considered (183 Graves, 383F, median age = 64y 17–89y]). Results. Median 131I administered activity was 385 MBq [66–629 MBq] and only 29% of the patients had the maximum allowed activity. Total administered activity was 209 GBq; if the standard activity of 600 MBq had been administered to all patients total would have been 302 GBq, 45% greater than the really used one. This acts on the patient mean effective dose and on the mean absorbed dose to the stomach wall (critical organ for 131I-NaI/ ICRP53) that were 5.8 Sv instead of 9.0 Sv and 177 mGy instead of 276 mGy respectively, with a maximum dose saving (9 times) for the patient who was given 66 MBq. The reduction of 131I administered activity also acts on the exposure of the nuclear medicine staff and of population: the mean dose rate at 1 m at the patient discharge time is 12 lSv/h instead of 20 lSv/h. This approach involves also the environment, as in the first 24 h 60% of administered activity is excreted. Conclusions. The application of a patient specific pretreatmentdosimetric study can reduce of 45% the radioprotection impact of 131 I treatments of hyperthyroidism with clinical results guaranteed and activity administered to the single patient can be decreased down to 9 times. https://doi.org/10.1016/j.ejmp.2018.04.348
340. Evaluation of worker inhaled activity after surface contamination C. Gori a, L. Fedeli a, R. Ropolo b a b
University of Florence, Dept. ‘‘Fisica e Astronomia”, Firenze, Italy A.O.U. Città della Salute e della Scienza di Torino, Torino, Italy
Purpose. The use of unsealed sources (either in nuclear medicine or in radiochemical bio-laboratories) involves the risk of internal contamination for workers after partial evaporation of the unsealed source during its use. This issue was already addressed in [1], the aim of this work is to extend that work towards a comprehensive model taking into account also the airborne contamination after radionuclide evaporation from the cumulated surface contamination of the working area. Methods. The above mentioned model takes into account the manipulation time (tm, the manipulated activity (A), the frequency of manipulations, the total time the workers spend in the laboratory (on an yearly basis), the air exchange ratio (R) and the half-life of the manipulated radionuclides. According to the actual working conditions, the model evaluates firstly the radionuclide air concentration as a function of time and thereafter the committed effective dose depending on the time spent in the laboratory by the worker. Results. During tm the radioisotope manipulation determines both air contamination (AC) and probabilistic surface contamination (SC). After tm AC decreases due to R, whereas surface contamination increases after each manipulation, decreasing only through physical decay, thus leading to an asymptotic SC in the long run. SC is more relevant for long-life radioisotopes. Conclusions. Application of the model to an actual bio-laboratory case shows that contribution to inhaled activity from surface con-