Magnetic resonance imaging (MRI) has been used to image the brain and other stationary organs within the body and has become widely available as a diagnostic technique for cardiovascular imaging. This has been possible because of sophisticated ECG gating and respiratory motion suppression methods that facilitate high-quality cross sectional images of the heart. It is now customary to use the term cardiovascular magnetic resonance (CMR) when referring to MRI of the heart and blood vessels.
Among the many techniques employed on MRI systems, three are the mainstays of clinical CMR .
●Spin echo imaging — Spin echo imaging depicts the tissue structures of the heart as bright and the blood pool as dark (black blood approach). The spin echo method is predominantly used for anatomical imaging, and for identifying the fatty infiltration of the right ventricular free wall frequently seen in arrhythmogenic right ventricular cardiomyopathy (ARVC) . (See "Clinical manifestations and diagnosis of arrhythmogenic right ventricular cardiomyopathy".)
●Gradient echo imaging — Gradient echo imaging generates images in which the blood pool appears bright and myocardium dark (bright blood approach). This technique is used to evaluate left and right ventricular cavity sizes and function, ventricular mass, intracardiac shunts, valvular functions, and to detect intracardiac masses. Steady state free precession (SSFP), a related approach, can generate high temporal (less than 30 msec) and spatial (2mm in-plane) resolution cine images in an 8 to 12 second breathhold.
●Flow velocity encoding — Flow velocity encoding (also known as phase contrast) is a technique that is used to directly measure blood flow and is useful for quantifying the severity of valvular regurgitation and stenosis, intracardiac shunt size, and the severity of arterial vascular stenosis .