What is coronary CTA, and how does it differ from routine chest CT?
Coronary CTA is a contrast-enhanced CT study optimized for visualization of the coronary arteries. On a regular CT scan of the chest, the heart appears blurred because of its motion, so coronary CT requires synchronization of image acquisition to the electrocardiogram (ECG) signal. The challenge of imaging the coronary arteries is compounded by the fact that these vessels are very small and move a large amount in every cardiac cycle. The left main coronary artery measures a maximum of 5 mm in diameter, and for much of their course the other arteries are only about 2 mm in diameter; therefore the resolution of the CT scanner must be in the submillimeter range. The right coronary artery can move up to 5 cm in each cardiac cycle—imaging a 2 mm structure that moves 5 cm in each direction every second is challenging. To acquire high-quality images, the following techniques are employed: ECG gating, multidetector image acquisition, fast gantry rotation, and, in some scanners, dual x-ray tubes.