CT acquisition protocol

All examinations were performed on a 384-slice third generation dual source CT scanner, SOMATOM FORCE (Siemens Healthineers, Forchheim, Germany) with temporal resolution of 66 milliseconds. CAC scoring was performed using both the conventional sequential protocol and the spiral (FLASH) mode protocol. Images were obtained extending from the carina to the cardiac apex. In the conventional sequential (step-and-shoot) protocol, prospective ECG-gated, non-contrast acquisition was performed at 70% of R-R interval. The imaging parameters included: tube voltage-120 kV, automated tube current modulation (CARE Dose4D, Siemens Healthcare, Forchheim, Germany) with reference tube current being 80 mAs. The images were reconstructed in the mediastinal window with slice thickness of 3 mm and increment of 1.5 mm using Qr36 kernel with model-based iterative reconstruction strength level 3 (ADMIRE; Siemens Healthcare, Forchheim, Germany) (Figure 1A).

Coronary artery calcium (CAC) scoring using conventional sequential protocol (A) and the spiral (FLASH) mode protocol (B) showing the CAC scores to be 108.2 and 115 respectively

The spiral (FLASH) mode utilized a high-pitch and high-speed gantry rotation scanning mode where acquisition of the entire heart was done within a single cardiac cycle with prospective ECG-gating at 70% of R-R interval. The imaging parameters included: tube voltage: 120 kV, pitch: 3.2 and automated tube current modulation (CARE Dose4D, Siemens Healthcare, Forchheim, Germany). Slices were reconstructed in mediastinal window of 3.0 mm section and increment of 1.5 mm using Qr36 kernel with model-based iterative reconstruction strength level 3 (ADMIRE; Siemens Healthcare, Forchheim, Germany) (Figure 1B).