Dose calibrator linearity test: 99mTc versus 18F radioisotopes*

OBJECTIVE The present study was aimed at evaluating the viability of replacing (18)F with (99m)Tc in dose calibrator linearity testing. MATERIALS AND METHODS The test was performed with sources of (99m)Tc (62 GBq) and (18)F (12 GBq) whose activities were measured up to values lower than 1 MBq. Ratios and deviations between experimental and theoretical (99m)Tc and (18)F sources activities were calculated and subsequently compared. RESULTS Mean deviations between experimental and theoretical (99m)Tc and (18)F sources activities were 0.56 (± 1.79)% and 0.92 (± 1.19)%, respectively. The mean ratio between activities indicated by the device for the (99m)Tc source as measured with the equipment pre-calibrated to measure (99m)Tc and (18)F was 3.42 (± 0.06), and for the (18)F source this ratio was 3.39 (± 0.05), values considered constant over the measurement time. CONCLUSION The results of the linearity test using (99m)Tc were compatible with those obtained with the (18)F source, indicating the viability of utilizing both radioisotopes in dose calibrator linearity testing. Such information in association with the high potential of radiation exposure and costs involved in (18)F acquisition suggest (99m)Tc as the element of choice to perform dose calibrator linearity tests in centers that use (18)F, without any detriment to the procedure as well as to the quality of the nuclear medicine service.