Radiation exposure in cardiac computed tomography imaging in Mie prefecture in 2021.

Purpose: Several effective radiation dose reduction methods have been developed for coronary computed tomography angiography (CTA); however, their use in daily clinical practice remains unknown. We aimed to investigate radiation exposure and the utilization of dose-saving strategies for coronary CTA in hospitals in Mie Prefecture, Japan.

Materials And Methods: Image acquisition details and dose reports of 30 consecutive cardiac CT examinations performed in 2021 were obtained from 18 hospitals. The inclusion criteria were patients aged 20-80 years who weighed 50-70 kg and underwent coronary CTA using ≥ 64-row multidetector CT. The doses for the overall cardiac CT examination and coronary CTA were analyzed using the dose-length product (DLP) and CT dose index (CTDIvol), respectively. Multivariate analysis was performed to determine independent predictors that affect the radiation dose in coronary CTA.

Results: The median DLP of cardiac CT was 774 (interquartile range [IQR]: 538-1119) mGy*cm, and the median CTDIvol of coronary CTA was 33 (IQR: 25-48) mGy. The 75th percentile values of DLP for cardiac CT and that of CTDIvol for coronary CTA were slightly lower than the values recorded in the Japan Diagnostic Reference Level (DRLs) 2020 report (1285 mGy*cm and 66.4 mGy, respectively) but were substantially higher than those reported in a previous large international dose survey (402 mGy*cm and 24 mGy, respectively). Iterative reconstruction was performed during all examinations. Only six hospitals (33%) used a low tube potential (≤ 100 kVp), and nine hospitals (50%) used electrocardiogram-triggered prospective scanning. Multivariate analysis revealed low heart rate, low tube potential, and use of electrocardiogram-triggered prospective scanning as independent predictors of CTDIvol ≤ 24 mGy (p < 0.001, respectively).

Conclusion: As of 2021, low tube potential and prospective scanning are underutilized, whereas iterative reconstruction is used in every coronary CTA in Mie Prefecture. Further efforts to optimize the radiation exposure from cardiac CT scans are necessary.