Cumulative radiation exposure from repeated CT imaging in hospitalised COVID-19 patients: Does it matter?

To assess cumulative radiation exposure associated with repeated CT imaging in hospitalized COVID-19 patients and to identify factors contributing to high cumulative dose.

This retrospective observational study included 69 adult patients with confirmed COVID-19 who underwent three or more CT examinations during a single hospitalization. A total of 296 CT examinations comprising 350 acquisition phases were analyzed. Dose parameters (CTDIvol, DLP) were recorded, and cumulative effective dose (CED) was calculated using region-specific conversion factors. Continuous variables were expressed as median with interquartile range (IQR).

The median cumulative effective dose was 47.7 mSv (IQR 34.5-87.2; range 18.0-342.6). A total of 32 patients (46.4%) accumulated ≥ 50 mSv, while 16 patients (23.2%) exceeded 100 mSv during a single hospitalization, including one patient (1.4%) with exposure ≥ 200 mSv. CED showed a moderate correlation with the number of CT examinations (ρ=0.37, p = 0.0016) and a stronger correlation with the total number of acquisition phases (ρ=0.54, p < 0.00001). Patients with CED ≥ 100 mSv had a higher median number of acquisition phases (5.5 vs 3), whereas the difference in the number of CT examinations was less pronounced (4.5 vs 4). Non-contrast chest CT accounted for 70.95% of all examinations.

Repeated and multiphase CT imaging resulted in substantial cumulative radiation exposure in a selected subgroup of hospitalised COVID-19 patients. Nearly one quarter of patients exceeded 100 mSv during a single hospitalisation. These findings support careful justification of repeated CT examinations, limitation of multiphasic acquisitions when clinically feasible, and systematic dose monitoring in patients requiring intensive imaging follow-up.