Incidence of exposure in PET/CT compared to the total dose taken by the nuclear medicine technical staff

Full text of publication follows. Aim: the 511-keV photons originated by the annihilation event have a penetration capacity 10-fold greater than the 140 keV gamma rays emitted by ^99mTc. The resulting increased radiation risk for technical staff is sometimes underestimated. The results of a prior pilot investigation had shown that, in our center, radiation exposure for technologists working with PET/CT before installation of the automatic injector was higher than for those working with conventional Nuclear Medicine, and was directly related to the number of scans performed. In this work we measured the actual radiation exposure for the technical staff employed for PET/CT and for conventional Nuclear Medicine, respectively, considering that for PET/CT we minimized radiation exposure by using an automatic injector. Methods: to measure the actual percentage of whole-body and extremities exposures (normally measured every 4 months with chest and wrist film dosimeters, respectively), throughout 2012 each technologist was equipped with two dosimeters, one of which was used only during the PET/CT sessions. Over that period each technologist performed about 500 conventional Nuclear Medicine scans (using mostly ^99mTc, but also ¹³¹I, ¹²³I and ¹¹¹In) and about 250 PET/CT scans (almost exclusively with [¹⁸F]FDG). Results: the range of exposures in 2012 turned out to be 0.5±0.3 mSv (range 0.23-1.04) for the chest dosimeter used in PET/CT, while it was 0.6±0.3 (range 0.21-1.24) for conventional Nuclear Medicine. Regarding the extremities, the dosimeter used only for PET/CT recorded 1.4±0.8 mSv (range 0.69-3.02), while they recorded 5.7±4.17 mSv (range 1.0-13.84) for conventional Nuclear Medicine. Conclusion: these results demonstrate that similar whole-body exposures are reached with about half the PET/CT scans versus the conventional Nuclear Medicine scans (0.5 mSv versus 0.6 mSv deriving from 250 versus 500 scans, respectively). The additional exposure from PET/CT activity to the extremities is instead less important 1.4 mSv for 250 PET scans versus 5.7 mSv for 500 conventional scans), most likely because of the reduced risk due to use of an automatic injector for PET. Instead, for conventional Nuclear Medicine the technologist has to handle more closely the radiopharmaceuticals prepared in the radiopharmacy. In order to further reduce the average dose accumulated by the technical staff, the development of optimal environmental pathways is required to ensure an adequate distance between the injected patient and the technologists. (authors)