Institutional clinical indication-based diagnostic reference levels and size-specific dose estimates in multiphasic abdominopelvic CT protocols in adult patients

Objective: In this retrospective study, we aimed to determine the clinical indication-based diagnostic reference levels (DRLci) and Size-Specific Dose Estimates (SSDE) of multiphasic abdominopelvic CTs. Materials and Methods: Multiphasic liver, kidney, pancreas and mesenteric ischemia protocol CT scans performed at Izzet Baysal Training and Research Hospital between January 2018 and December 2021 were analyzed. CTDIvol and DLP values were recorded, SSDE and ED (effective dose) values were calculated. SSDE calculation was made with water equivalent diameter (Dw). Results: The total number of patients was 514, and 46 patients excluded from the study. As the height and weight of the patients were not known, 42 patients with CTDIvol and DLP values in the minimum and maximum 5% range were not included in the DRL calculation. DRLs were calculated on 426 patients (183 women, 243 men; 111 liver, 120 renal, 85 pancreas, 110 mesenteric). The 75th percentile values were given for DRL. Clinical indications were hepatocellular carcinoma, renal cell carcinoma, pancreas adenocarcinoma, and mesenteric ischemia. We found DRLs for CTDIvol, DLP, SSDE, and ED were 11.17 mGy, 1074.31 mGy.cm, 13 mGy, and 16.43 mSv for liver CT; 10.07 mGy, 1163.16 mGy.cm, 12.07 mGy and 17.79 mSv for kidney CT; 10.1 mGy, 701.26 mGy.cm, 12.04 mGy and 10.72 mSv for pancreas CT; 11.45 mGy, 1230.05 mGy.cm, 15.13 mGy and 17.09 mSv for mesenteric CT, respectively. Conclusion: This is the first national and international DRLci and SSDE study of multiphasic abdominopelvic CT protocols. As standardized protocols are not widely used for multiphasic CTs, resulting in large differences in DRLs between different scanners, institutions and countries. It is recommended to ensure protocol standardization, and in cases where it cannot be achieved, to evaluate periodical DRL in their own institution. In this way it is possible to detect unforeseen deviations in patient doses in routine clinical practice and to correct them. When taken into account of the frequent use of multiphasic abdominopelvic CT examinations, causing the highest medical ionising radiation exposure, it is obvious that there is an urgent need for more comprehensive DRL studies at national and international level.