Radiation Protection During Cyclotron Production of Radiopharmaceuticals

Positron emission tomography (PET) is a radiological diagnostic procedure very suitable for follow up of many oncologic diseases, but can also be efficiently used in diagnostic and follow up of some cardiologic and neurologic diseases too. The most often used radiopharmaceutical, fludeoxyglucose F-18, is produced in the 18 MeV cyclotron in RudJer Medikol Cyclotron d.o.o. (RMC) by the proton bombardment of enriched water H218O. During the whole production cycle the operatives in charge of producing FDG-RMC are, however, exposed to potentially harmful γ-radiation generated either by the operation of cyclotron (proton induced primary, and neutron induced secondary), or to the decay of generated radioisotope 18F, and for their full protection we have implemented the ALARA concept systematically. We have divided the cyclotron operators in three categories depending on the type of activities and the length of potential radiation exposure, and paid special attention to distribute their tasks in such a manner that the overall accumulated dose is approximately equal for all of them. Prior to full operation we have estimated the annual accumulated dose for each operator on the basis of maximum produced activity of 370 GBq (10 Ci) 18F, and dose rate measurements performed by the approved service for radiation protection and radiation monitoring - EKOTEH dosimetry d.o.o. (Thermo Radiameter FH 40-L10, Ser. No. 20268). In this work we report the actual measurements for the period of first three months of regular production (1.11.2010.-31.1.2011.) done by thermoluminescent LiF:Mg,Ti dosimeters Harshaw (TLD-100, type: BG0110). The readings have been done by two automatic personal dosimeter readers Harshaw 6600 by the Rudjer Boskovic Institute licensed service. The measured values were for the observed period much lower than the maximum estimated values, confirming our theoretical model and radiation protection scheme. We have also estimated the rise of absorbed doses due to probable increase in size of production, and concluded that the absorbed doses in these cases will also be within acceptable limits. Therefore, we conclude that the radiation protection at RMC is systematically kept well under legally allowed limits, and ALARA concept is fully implemented. (author)