What question did this study set out to answer?

The study aims to assess cumulative radiation exposure from recurrent CT imaging and establish a local reference level.

February 16, 2026Open Access

Recurrent CT imaging and strategies for patient radiation protection

AJAntonio JreijeKaunas University of Technology LKLeonid KrynkeVilnius University Hospital Santariskiu Klinikos BGBirutė GricienėVilnius University

Key Points

The study aims to assess cumulative radiation exposure from recurrent CT imaging and establish a local reference level.
Retrospective analysis of adult CT examinations over two years at a tertiary care hospital.
Identification of recurrent patients based on CT history in 2022, 2023, or 2024.
Measurement of cumulative effective doses (CED) and determination of a Recurrent Exposure Reference Level (RERL).
78,258 patients underwent 99,865 CT examinations over three years.
Yearly incidence of patients with CED ≥100 mSv remained stable at ~2%.
3.6% of patients exceeded 100 mSv; 0.04% exceeded 500 mSv.
Among recurrent patients, 18.2% exceeded 100 mSv within three years.

Abstract

Abstract Background: Computed tomography (CT) contributes disproportionately to medical radiation exposure. While most patients undergo only a few examinations, a subset accumulates high cumulative effective doses (CEDs), raising concern for long-term stochastic risks. Recently, the concept of a Recurrent Exposure Reference Level (RERL) has been proposed as a benchmark for cumulative dose monitoring in recurrently imaged patients.Aim: To evaluate cumulative radiation exposure from recurrent CT imaging in a tertiary care hospital, determine the proportion of patients exceeding high-dose thresholds, and establish a local RERL.Methods: All adult CT examinations performed at Vilnius University Hospital Santaros Klinikos between 2022 and 2024 were retrospectively analyzed. Recurrent patients were defined as those with at least one CT in 2023 and an additional CT in 2022, 2023, or 2024. Outcome measures included the annual and three-year incidence and prevalence of CED ≥100 mSv, dose distributions, and RERL determination as the 75th percentile of annual CED among recurrent patients.Results: Over three years, 78,258 patients underwent 99,865 CT examinations. The annual number of patients and exams increased steadily, but the yearly incidence of high-dose patients (CED ≥100 mSv) remained stable at ~2%. Across the full cohort, 1,633 patients (3.6%) exceeded 100 mSv, and 29 patients (0.04%) surpassed 500 mSv. Among 9,199 recurrent patients (35.6% of the total), 18.2% exceeded 100 mSv within three years. Most patients (68%) crossed this threshold with fewer than five CTs. The local RERL, defined as the 75th percentile of annual CED in recurrent patients, was 36 mSv.Conclusion: A subset of patients in a tertiary care setting accumulated high radiation doses from recurrent CT, often with relatively few examinations. The derived RERL aligns closely with values reported in other European studies, supporting its use as a practical benchmark for monitoring cumulative dose. Systematic dose tracking, integration of RERLs, and strict adherence to justification and optimization are essential to mitigate risks while preserving the diagnostic value of CT.

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