Effect of through-plane motion on left ventricular rotation: a study using slice-following harmonic phase imaging.

Noninvasive quantification of regional left ventricular rotation may improve understanding of cardiac function. Current methods used to quantify rotation typically acquire data on a set of prescribed short-axis slices, neglecting effects due to through-plane myocardial motion. We combine principles of slice-following tagged imaging with harmonic phase analysis methods to account for through-plane motion in regional rotation measurements. We compare rotation and torsion measurements obtained using our method to those obtained from imaging datasets acquired without slice-following. Our results in normal volunteers demonstrate differences in the general trends of average and regional rotation-time plots in midbasal slices and the rotation versus circumferential strain loops. We observe substantial errors in measured peak average rotation of the order of 58% for basal slices (due to change in the pattern of the curve), -6.6% for midventricular slices, and -8.5% for apical slices; and an average error in base-to-apex torsion of 19% when through-plane motion is not considered. This study concludes that due to an inherent base-to-apex gradient in rotation that exists in the left ventricular, accounting for through-plane motion is critical to the accuracy of left ventricular rotation quantification.