Keywords: Cardiovascular: Cardiac
The heart exhibits complex motion due to cardiac contraction and respiration. ECG and diaphragm navigators have been commonly used for the past two decades. However, these classic techniques have limitations such as distortion of ECG due to magnetohydrodynamic effects. Self-gating directly extracts physiological motion from the image data, allowing 5D imaging of coronary arteries without ECG. Pilot tone utilizes a small antenna to transmit a continuous RF and MR receiver coils to capture modulated RF signal by cardiac and respiratory motion. External devices such as Doppler ultrasound, acoustic sensors and photoplethysmography have also emerged as methods alternatives to ECG gating.