Right ventricular midwall surface motion and deformation using magnetic resonance tagging.

We describe a method for reconstructing the three-dimensional motion and deformation of the midwall surface of the right ventricular free wall (RVFW) using magnetic resonance tissue tagging. Tag points were defined where the tag stripes intersected the midwall contour and were tracked through systole in both short- and long-axis images. A finite-element model of the midwall surface of the RVFW was constructed to fit the midwall shape at end diastole. The model was then deformed to each subsequent frame by fitting the tag displacements and midwall contour locations. The method was applied to two human studies, a normal subject and a patient with right ventricular hypertrophy. The root mean squared error between model tag planes and tracked tag points was 0.70 mm for the normal heart (180 points) and 0.67 mm for the hypertrophic heart (52 points), both less than the image pixel size of approximately 1.0 mm. The differences in contraction patterns were visualized between the two studies. We conclude that this method allows accurate, noninvasive measurement of in vivo RVFW deformation.