Fine resolution 3D displacement measurements of mouse left ventricle using orthogonal sets of 2D B-mode ultrasound images

Fine spatial and temporal resolution of 3D displacement field in the mouse left ventricle (LV) is reconstructed from finely sampled stacks of 2D orthogonal images. Using orthogonal 2D image stacks allows for each of X, Y and Z direction displacement vectors to be detected. Serial short-axis (SA) and long-axis (LA) images of both healthy and infarcted mouse left ventricles were acquired at 0.5mm intervals using a linear array transducer operating at 30MHz. Myocardial motion was tracked using a 2D minimum sum of absolute difference (MSAD) speckle tracking technique. In regions experiencing image artifacts or signal dropout, an incompressible tissue mathematical model was employed, and motion was corrected based on a weighted average of tracked motion and model predicted values. Displacement error was computed based on the ratio of final displacement to the length of the trajectory through the entire heart cycle. By incorporating an incompressible LV mathematical model, tracking error was reduced from 8.4±1.4% to 5.6±1.2%. 3D analyses of cardiac motion provide a more comprehensive assessment of post-infarct ventricular function than conventional 2D analyses. For example, after evaluating the relative displacement magnitudes of post-infarct hearts, dysfunctional myocardium was localized to the apical-anterolateral region of the LV. In the dysfunctional tissue, average radial, circumferential, and longitudinal displacements were reduced by 45.1±9.8%, 43.5±8.2%, and 52.4±9.2%, respectively.