Motion Analysis of Both Ventricles Using Tagged-MRI in Paced Canine Hearts

Methods For this study, tagged MRI images (see Fig.1) were acquired from canine hearts while pacing with standard cardiac gated, breath-hold, cine SPGR, no echo sharing or interpolation, in a 1.5T cardiac scanner. (GE Medical Systems). Following myocardial and tag segmentation a four-dimensional B-spline based parametric motion field was computed for a volume of interest encompassing both ventricles. Using this motion field, 3D displacements, velocities and strains were calculated for the RV and LV. The circumferential strain (Ecc) is commonly used for the analysis of the LV. For the RV, we chose the Ecc direction tangential to the RV surface and parallel to the short axis imaging plane. The Ecc range [∆Ecc = (the end diastolic Ecc)-(the end systolic Ecc)] was calculated at 20 mid-wall locations over the RV and the spatial inhomogeneity of this parameter was evaluated using coefficient of variation (CV): CV = (standard deviation of ∆Ecc) / (mean ∆Ecc).