Motion measurement has the potential to be used as a diagnostic tool for assessment of heart disease and as a theoretical tool for physiological analysis. Past approaches for measuring heart motion can be divided into two types. The second type of approach uses tagged magnetic resonance imaging techniques to estimate the displacement field for all points within the heart. Here we present a technique that uses the standard MR tagging protocol, but measures motion at a discrete set of material points as in the material marker methods. This technique may be used to compare the merits of MR tagging to material marker techniques, or to provide data to existing analysis routines intended for use with material marker data.
Tags appear as dark regions in the images that move with an object as it moves.
Tagging is particularly valuable in cardiac imaging because the tissue in the walls of the heart provides few natural features for motion tracking. An example of a tagged heart image is shown at left, where the ring shaped object is the wall of the left ventricle. The tag pattern used was originally a set of parallel stripes and this image was taken after heart motion had deformed the stripes into the bent lines you see here. Click on the image to see a 10 frame mpeg movie demonstrating the deformation of the tag lines from their original straight configuration. This concept is illustrated in the next image below, which shows a single tag surface intersecting a set of images.