Assessment of patient doses and corresponding radiation risks from PET/CT examinations in the Russian Federation

In the current study we evaluated the structure of positron emission tomography combined with computed tomography (PET/CT) diagnostics in the Russian Federation. Patient effective doses, organ doses and corresponding radiation risks for the most common PET/CT examinations were evaluated. Data was collected in 12 regions of the Russian Federation in the period 2012-2017 in 19 facilities (26 PET/CT scanners, corresponding to more than 60 % of the scanners in the country). Typical administered activities and DLP values for the CT protocols were estimated with the subsequent calculation of typical organ and effective doses from external and internal exposure. Lifetime radiation detriment-adjusted risks were calculated based on both the effective dose and organ absorbed doses considering the gender of the patient. The results of the dose survey indicate that the most common PET/CT examinations are whole body and brain examinations with 18F-FDG (performed in 26 and 8 surveyed departments respectively). Other PET/CT examinations are significantly less common. The highest patient doses were calculated for whole body PET/CT examinations - about 20 mSv. The doses increase up to 35-40 mSv if multiphase CT scan was performed, the CT scan composed up to 70-90 % of the total effective dose. Lifetime detriment-adjusted risk was estimated for PET/CT examinations of the brain as 2·10 ^-4 ; for pelvic as 5·10 ^-4 , and may reach up to 10 ^-3 for whole body PET/CT examinations. Comparison of risks assessed by two approaches indicated that the simplified risk assessment based on effective dose overestimated the risk for PET/CT examinations of the brain (both genders) and for whole body and pelvic examinations (males only). Overall, differences in male and female patients can reach up to the 30 %.