Abstract 391: Feasibility and Image Quality of a New Sub-mSv Coronary CT Angiography Protocol Using Prospectively ECG-Triggered High-Pitch Spiral Acquisition
Introduction: Coronary CT angiography (CTA) provides clinically useful information in selected patients, but high radiation exposure has been a limitation. We evaluated the feasibility and image quality of a new scan mode, prospectively ECG-gated high-pitch spiral imaging, for coronary CTA with an effective dose below 1 mSv.
Methods: 60 consecutive patients referred for ruling out coronary stenoses were studied. Selection criteria were absence of previously known coronary disease, body weight ≤ 100 kg, and sinus rhythm < 60 beats/min after pre-medication with beta blockers. 60 ml contrast agent were injected. Coronary CTA was performed using a Dual Source CT system (Siemens Definition FLASH) with 2×128×0.6 mm collimation, 0.28s rotation time, a pitch of 3.2 (first 28 patients or 3.4 (32 patients), 100 kVp tube voltage and a tube current of 320 mAs. Data acquisition was triggered at 60% of the R-R interval and was completed within 1 cardiac cycle. Images reconstruction used 75 ms temporal resolution, 0.6 mm slice thickness and 0.3 mm increment. Image quality was evaluated using a 4-point scale (1 = absence of any artifacts; 2= slight artifacts, fully evaluable; 3 = artifacts, evaluable, 4 = uninterpretable) using the SCCT 18-segment model.
Results: Out of 81 patients screened for inclusion, 21 were excluded: 11 because heart rate remained > 60/min even after beta blockade, and 10 for a body weight > 100 kg. In all 60 included patients, imaging was successfully performed. Mean heart rate before and during coronary CTA was 70±11 and 52±4 beats/min. Mean scan length was 117±9 mm, mean duration of data acquisition was 258±20 ms. Mean dose-length product was 62±5 mGy*cm, the resultant mean effective dose was 0.87±0.08 mSv (range: 0.78 – 0.99 mSv). Of 896 coronary artery segments, 847 (95%) had an image quality score of 1, 36 segments (4.6%) a score of 2, 8 segments (1.0%) a score of 3, and 4 segments (0.4%) were “uninterpretable”.
Conclusion: In non-obese patients with a low and stable heart rate, coronary CTA using prospectively ECG-triggered high-pitch spiral acquisition can be performed with high image quality and a consistent radiation dose below 1.0 mSv.