Motion compensation

This chapter introduces the different methods used to synchronize pulse sequences with both cardiac and respiratory motions, to suppress motion-related blurring and image artefacts. A single frame or a series of images (cine imaging) can be acquired at different time points (cardiac phases) throughout the cardiac cycle by detecting the patient’s heart rate, usually by using an electrocardiogram (ECG) or, in case of poor ECG signals, a pulse oximeter signal. Fast single-shot and segmented k-space acquisition techniques are introduced, and for segmented cine imaging, both prospective and retrospective gating techniques are described. To suppress breathing motion artefacts, acquisitions use respiratory motion techniques. For short acquisition durations, breath-holding is the easiest method to stop the patient’s breathing during data collection. However, for long scans, respiratory gating or respiratory navigated techniques can be used. The principles of these techniques and their applications are presented.