Calcium Scoring with Prospective ECG-Triggered coronary CT Angiography: A Path to Reduce Radiation Dose

Abstract

Abstract Objectives: To examine if calcium scoring CT (CAS-CT) reduces the whole-examination radiation dose of prospectively ECG-triggered coronary CT-angiography (CCTA). Methods In this retrospective study, patients underwent CAS-CT and prospectively ECG-triggered CCTA on a 2nd generation Dual-Source CT scanner. CCTA was planned on CAS-CT images. We further simulated CCTA-planning on scout-view. Therefore, the scan length of the scout-view-derived CCTA was set equal to the CAS-CT scan length. Effective doses were compared for the following scenarios: (1) CAS-CT-derived CCTA + CAS-CT and (2) scout-view-derived CCTA without CAS-CT. Dose differences between the scenarios were additionally examined with respect to scan mode and body-mass-index. Results Among 182 patients (58±12 years, 47% females), planning cCTA on CAS-CT resulted in a shorter scan length than planning on scout-view (114.3 ± 9.7 mm vs 133.7 ± 13.2 mm, p<0.001). The whole-examination effective dose was slightly lower for scenario (1) (3.2 [1.8 – 5.3] mSv vs 3.4 [1.5 – 5.9] mSv; p<0.001, n=182). Scenario (1) resulted in a substantially lower radiation dose in sequential scans (3.6 [2.3 – 6.1] mSv vs 3.9 [2.4 – 6.50] mSv, n=150), or in obese patients (6.8 mSv [4.5 – 9.1]) vs 7.3 mSv [4.7 – 9.9], n=45), p<0.001 respectively. Only in high-pitch spiral CCTA, scenario (2) resulted in a dose salvage (0.8 mSv [0.6 – 1.4] vs 1.0 mSv [0.8 – 1.5], n=32; p<0.001). Conclusions Planning prospectively ECG-triggered CCTA on CAS-CT reduces the overall radiation dose of the examination compared to a scout-view planning approach where no CAS-CT is acquired. Only for high-pitch spiral CCTA a slightly opposite effect was observed.