Measurements and calculation of local radiation doses in the vicinity of a positron emission tomograph (PET)

To assess the possible radiation dose from PET studies to personnel working in the vicinity of a PET scanner, local doses were measured with LiF thermoluminescence dosemeters at five different positions (maximum distance from the scanner 5.33 m) within the PET area, during a one year period. For the 692 clinical, and physical, PET measurements carried out during the same 12 month period the doses at the five positions were calculated and compared with the measured local doses. In the calculation, absorption and scattering of annihilation quanta was taken into account with geometry factors determined with a separate dose measurement using a strong 198Au source of 11.26 GBq (304 mCi), centred in the field of view of the tomograph. Measured local doses ranged from 0.86 mSv to 3.80 mSv (including the natural background of 0.70 mSv). The range of the corresponding calculated doses was 0.90-4.21 mSv. Good agreement existed between measured and calculated doses, demonstrating the validity of the calculation method. The results show that the calculations are applicable for predicting local doses in the vicinity of planned PET installations. (Author)