Assessing trends in patients undergoing recurrent CT examinations and cumulative doses

Recent research has enhanced our understanding of the number of patients receiving relatively high radiation doses (≥100 mSv) through recurrent CT examinations. However, there is a paucity of information on temporal trends. This study elucidates these trends over the past 11 years.

We retrieved data on CT exams conducted from 2013 to 2023 from our hospital's dose-management system. We analyzed the number of patients undergoing recurrent CT examinations, calculated the median cumulative effective dose (CED), and assessed the frequency of patients receiving doses of ≥ 50 mSv and ≥ 100 mSv. Generalized linear models that accounted for autocorrelation via Newey-West covariance estimates and non-linearities due to the COVID-19 pandemic were employed to quantify temporal trends.

Among 403,997 patients in 11 years, 46.3 % had 1 CT exam, 53.7 % received ≥ 2 exams, 20.3 % received ≥ 5 exams, and 8.3 % had ≥ 10 exams, with 6.6 % having CEDs ≥ 100 mSv. The rate of recurrent exams decreased post-2020 (incident rate ratio, IRR: 1.029, 95 % CI 1.025, 1.033). The median CED increased post-2020 relative to pre-2020 (difference in annual changes: -0.102, 95 % CI -0.119, -0.085). Patients with new annual doses ≥ 100 mSv decreased post-pandemic (IRR: 0.976, 95 % CI 0.955, 0.997).

In this study examining temporal trends, the percentage of patients undergoing multiple CT examinations has changed since 2020, with a shift from an increasing to a decreasing trend in those receiving cumulative doses ≥ 100 mSv per year. This suggests an alteration in imaging practices or patient demographics since 2020, providing valuable insights to inform policymaking.