Non invasive measurement of myocardial motion using magnetic resonance tagging.

Magnetic resonance imaging has become a key modality within the modern radiology department. In addition to the conventional slice images, three dimensional angiographic images, and quantitative flow measurements can be obtained. More recently methods have been developed which enable one to visualize the motion of objects through the application of magnetic resonance markers or tags. Generally the myocardium appears homogeneous with respect to magnetic resonance imaging. Thus at best the displacement of the myocardial surfaces can be observed, but rotational and shear motions are not discernable. With magnetic resonance tagging this all changing. Tagging involves modifying the ability of the tissue to produce a nuclear magnetic resonance signal, in a spatially dependent manner. Typically the pattern is a grid of reduced signal intensity. The tagging grid is applied prior to the heart contraction. Then images are made during systole and diastole. The rotation and shear of the myocardium can be inferred from the distortions of the tagging grid. Here our work in this field is reviewed.