Comparative Assessment of the Absorbed Doses Resulted from Occupational Exposure and Computed Tomography
A comparative assessment of the absorbed doses resulted from computed tomography (CT) examinations, and the dose resulted from occupational external gamma exposure of the “Mayak” workers was carried out. The patients’ diagnostic radiation dose was reconstructed using Monte-Carlo simulation on a population of 58 virtual adult phantoms across 13 CT protocol categories. Archival records of CT examinations of patients were used for the dose reconstruction. Information on technical parameters of scanning was extracted from DICOM files. The study sample has been linked to the Mayak worker register database to identify persons who had professional contact with ionizing radiation. Annual occupational dose records for the Mayak workers were obtained from the Dose-2013 dosimetry system. In this study, information on 212 patients was collected from 303 records. Among them, 42 Mayak employees were identified, including 24 persons who had non-zero dose of external gamma radiation, and 16 persons with internal alpha radiation dose due to occupational intake of239Pu. Individual doses absorbed in the organs resulted from exposure to computed tomography and occupational activities has been compared. The results showed significant variability of the absorbed organ dose depending on the area of CT examination. The brain and lens were subjected to the highest radiation exposure during head CT. The average absorbed dose in brain was 24.5 mGy per single examination (the maximum brain dose accumulated over the entire study period was 82.3 mGy), and 27.7 mGy for the lens of the eye (the maximum lens dose reached 92.9 mGy). Relevant comparison of the absorbed dose of diagnostic and occupational exposure, accumulated during one year, has been performed. The average estimate of cumulative radiation dose absorbed in the organs during computed tomography was an order of magnitude lower than the one from occupational external gamma exposure of Mayak personnel, except brain dose. Annual CT dose equivalent of external gamma radiation was 2.82.
