A particular point in the cardiac cycle.

See also Arrhythmia Rejection.

Cardiology is a medicine sector that covers the clinical study, treatment and imaging of the heart actions and diseases.

See also Ischemia, Calcium Score, Cardiac Phase, Diastole, Adventitia, Defibrillator, ECG Trigger, Arrhythmia Rejection.

(CCTA) Coronary computed tomography angiography is a diagnostic imaging procedure to visualize the coronary arteries. CCTA is a non-invasive angiogram that allows the assessment of narrowed and clogged arteries that can cause heart attack and stroke.
Coronary CTA is a non-invasive alternative to traditional angiography that offers detailed images of heart function, resulting in faster, more accurate diagnosis. It helps stratify cardiac risk in patients with low to intermediate likelihood of coronary artery disease. For some patients with chest pain, coronary CTA can rule out the need for cardiac catheterization.
Coronary imaging requires a very fast CT scan, because the coronary arteries and other cardiac structures move rapidly during the cardiac cycle. The current 'state of the art' 64 slice multi-detector row CT systems rotate around the patient in less than 500 ms. The data must be acquired monitored by an electrocardiogram, which allows the computer to reconstruct retrospectively slices at different small segments of the cardiac cycle. This cardiac synchronization reduces motion artifacts in the coronary arteries and provides movies of the beating heart and valve motion.
See also Coronary Angiogram, Calcium Score, Cardiac Phase, Cine Mode and Defibrillator.

Gating is the synchronization of imaging with a phase of the cardiac or respiratory cycles.
A variety of means for detecting these cycles can be used, such as the ECG, peripheral pulse, chest motion, etc. The synchronization can be prospective or retrospective.