Assessment of CT doses and practices based on large data collected over four years in six hospitals of regional health network.

INTRODUCTION: Computed tomography (CT) contributes substantially to medical radiation exposure, and considerable dose variation has been reported across scanners and facilities. This study evaluated CT radiation doses and practices across eight CT scanners in six facilities within a regional healthcare network in Canada. The primary objective was to identify opportunities for dose optimization and enhance patient radiation protection across the regional network. METHODS: Data were collected retrospectively from January 1, 2020, to December 31, 2023, using a radiation dose monitoring system. Effective doses (EDs) were estimated using dose-length-product (DLP) based on ICRP103 tissue weighting factor. Exams with ED ≥ 15, 25, 50, 75, and 100 mSv were assessed. RESULTS: Over four years, 141,425 patients underwent 350,260 CT examinations, averaging 2.5 exams per patient; 25 % of patients were under 50 years old. The number of CT scans per 1000 population increased from 156 in 2020 to 184 in 2023, representing an 18 % increase over four years. The annual ED per capita increased by 20 %, from 1.23 mSv to 1.48 mSv over the same period. Median [average] EDs were 2.1 [2.3] mSv for the head, 3.8 [5.6] mSv for the thorax, and 9.4 [13.7] mSv for the abdomen-pelvis. Cardiac CT had the highest median ED of 19.7 mSv. Dose distribution analysis showed that 13.5 % of examinations had doses ≥15 mSv, 5.5 % ≥25 mSv, 1.0 % ≥50 mSv, 0.2 % ≥75 mSv, and 0.04 % ≥100 mSv. Additionally, 13.0 % of abdomen and abdomen-pelvis exams had doses ≥25 mSv. Among age groups, 1.1 % of exams for patients aged 0-10 years, 3.5 % for those aged 10-20 years, and 8.8 % for those aged 20-30 years resulted in doses ≥15 mSv. CONCLUSIONS: The findings highlight a substantial proportion of CT exams involving doses ≥25 mSv. Doses for abdomen-pelvis and cardiac procedures exceed published values, underscoring the need for dose optimization. PLAIN LANGUAGE SUMMARY: CT scans are an important part of healthcare, but they also contribute to a person's exposure to medical radiation. This study reviewed >350,000 CT examinations performed across six healthcare facilities in Canada to examine radiation doses and identify opportunities for improvement. This study found that CT use and overall radiation exposure increased over time, and that some types of scans, especially abdomen-pelvis and cardiac CT, often involved higher radiation doses than published reference values. This matters because identifying where doses are highest can help healthcare providers improve radiation safety while maintaining the benefits of CT imaging.