Detailed motion analysis of the left ventricular myocardium using an MR tagging method with a dense grid

Detailed analysis of myocardial deformation through a whole cardiac cycle w as accomplished using a tagging method with a high-density grid. Four sets of tagged images with a 4-mm-spacing grid were measured by generating four tagging pulses arranged at regular intervals in the cardiac cycle. Through each set of images, tag intersections were tracked semi-automatically. The estimated motions of tag intersections were concatenated so that sequential positions of myocardium were connected through a whole cardiac cycle. In v itro evaluation of the precision of this technique showed that the mean err or of tracked 4-mm tag intersections was less than 0.47 +/- 0.17 mm, even o n the quite low-contrast images, and the concatenation error caused by doub le concatenation was comparable to the interpolation error in the subendoca rdial area obtained with 8-mm tag intersection motion. The small difference between the two mean distance curves of the in vivo evaluation indicated t hat the method is useful for analyzing heart wall abnormalities. (C) 2000 W iley-Liss, Inc.