9A-3 Clinical Validation of Angle-Independent Myocardial Elastography Using MRI Tagging

In this paper, two-dimensional angle-independent myocardial elastography (2DME) was employed in order to assess and image myocardial deformation (or, strains) in an entire left-ventricular view and was further validated against tagged magnetic resonance imaging (tMRI) in normal as well as abnormal human subjects. Both RF ultrasound and tMRI frames were acquired in a 2D short-axis (SA) view at the papillary muscle level. In 2DME, in-plane (lateral and axial) incremental displacements (i.e., between two consecutive RF frames) were iteratively estimated using 1D cross-correlation and recorrelation techniques in a 2D search with a 1D matching kernel. The incremental displacements starting from end-diastole (ED) to end-systole (ES) were then accumulated to obtain cumulative systolic displacements. In tMRI, cardiac motion was obtained using a template-matching algorithm on a 2D grid-shaped mesh. The entire displacement distribution within the myocardium was obtained by a cubic B-spline-based method. In both 2DME and tMRI, 2D Lagrangian finite systolic strains were calculated from cumulative 2D displacements. Principal strains, which were angle-independent and less centroid dependent than polar (i.e., radial and circumferential) strains, were then computed from the 2D finite strains through our previously established strategy. Both qualitatively (or, full SA view) and quantitatively (or, temporal strain profiles), 2DME is shown capable of estimating myocardial deformation highly comparable to tMRI estimates in a clinical setting.