ECGtriggered

ECG-triggered, or ECG-gated, refers to the synchronization of image acquisition to the electrical activity of the heart using an electrocardiogram (ECG) signal. The goal is to capture data during specific phases of the cardiac cycle when motion is minimized, thereby reducing motion artifacts and improving the accuracy of measurements such as ventricular volumes and function.

Two main triggering approaches are used: prospective triggering, where data collection starts at predefined points in the cardiac cycle (typically after the R-wave) and occurs within a defined window; and retrospective triggering, where continuous data is acquired and later sorted into phases for reconstruction, enabling cine imaging across the cycle. ECG triggering is widely used in cardiac magnetic resonance imaging (MRI) and in computed tomography (CT), including coronary CT angiography, as well as in certain nuclear medicine protocols.

Applications include assessment of ventricular function in MRI, detailed cine imaging of cardiac chambers, evaluation of myocardial perfusion, and reducing motion artifacts in gated CT studies such as coronary angiography. Advantages include improved temporal resolution of cardiac motion, clearer delineation of end-diastolic and end-systolic frames, and enhanced diagnostic confidence. Limitations include reliance on a stable heart rhythm; arrhythmias can degrade timing accuracy, retrospective gating can extend acquisition times and, in CT, may increase radiation dose, and mis-triggering or ECG noise can compromise image quality. Proper ECG lead placement, rhythm monitoring, and protocol selection are essential, with specific choices influenced by heart rate, rhythm stability, and the imaging modality used.