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

To characterize recurrent CT examinations and cumulative effective dose (CED) prevalence across observation periods of one to five years in a Canadian hospital network.

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.

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.

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.

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.