ECGGating

ECG gating, also written ECG-gating, is a technique used in medical imaging to synchronize image acquisition with the cardiac cycle by using the electrocardiogram signal. By timing data collection to a specific phase of the heartbeat, gating reduces motion artifacts caused by cardiac motion and enhances the ability to assess cardiac structure and function.

In computed tomography (CT), there are two primary gating approaches. Prospective gating triggers data acquisition at predefined cardiac phases, typically diastole, and usually reduces radiation dose but can be vulnerable to heart-rate variability or arrhythmias. Retrospective gating records data continuously throughout the cardiac cycle and reconstructs images at multiple phases, enabling functional analysis of motion and volumes but at a higher radiation dose.

In magnetic resonance imaging (MRI), ECG gating coordinates data acquisition to the R-wave. Prospective gating triggers acquisitions at set times in the cardiac cycle, while retrospective gating collects data throughout the cycle and sorts it afterward for reconstruction. Cardiac gating is essential for cine MRI, where repeated rapidly acquired images show heart motion and enable measurements of ejection fraction, stroke volume, and wall motion. Gating performance can be affected by unstable ECG signals in the MRI environment or irregular heart rhythms.

Limitations include susceptibility to arrhythmias and heart-rate variability, signal degradation or interference with the ECG leads, and, in CT, radiation exposure. The choice of gating strategy depends on clinical goals, patient rhythm, and the balance between image quality, temporal resolution, and radiation dose.