Recurrent CT Examinations and Cumulative Effective Dose Prevalence: A Five-Year Regional Hospital Network Study

Abstract Purpose To characterize recurrent CT examinations and cumulative effective dose (CED) prevalence across observation periods of one to five years in a Canadian hospital network. Methods Data from eight CT scanners were analyzed for 2020–2024, with effective doses estimated from dose–length product (DLP) using standard conversion factors. Cumulative prevalence of recurrent examinations and high CED was assessed across progressively longer observation periods. Results A total of 413,680 CT examinations were performed on 161,420 patients, of whom 26% were aged 50 years or younger. Across one to five years, the proportions of patients undergoing five or more examinations were 3.8%, 7.0%, 9.6%, 12.2%, and 13.8%, respectively. Patients receiving CED ≥100 mSv over the same periods were 0.6%, 1.1%, 1.6%, 2.0%, and 2.3%. Notably, 233 patients aged 30 years or younger received a CED ≥50 mSv, representing 1.7% of all patients in this age group and 1.8% of all patients with a CED ≥50 mSv. Conclusions Recurrent CT examinations and high CED were observed among younger patients within five years. These findings highlight the importance of ensuring imaging-referral appropriateness and optimizing radiological practices to minimize unnecessary radiation exposure. Monitoring CED and recurrent imaging may provide useful population-level indicators for reviewing imaging practices and supporting ongoing optimization and radiation-protection efforts. Advances in knowledge This multi-period analysis provides population-level benchmarks for recurrent CT use and cumulative radiation exposure while clarifying how prevalence changes with observation-window length.