High resolution quantification of myocardial motion in mice using 2d speckle tracking

Mid-ventricular myocardial tissue motion in mice was examined using high resolution ultrasound B- mode images. The mouse heart was imaged at 35MHz, with approximately 40μm axial resolution and 100μm lateral resolution. Over 100 image frames per cardiac cycle were used in the analysis. Myocardial motion was tracked between successive image frames using a 2D minimum sum of absolute differences (MSAD) applied to 2D pixel kernels. The method is computationally efficient and a processing speed of 0.11 second per tracked image frame was achieved on a 2.9GHz Pentium IV PC, nearly 100X faster than in MATLAB. In the normal mouse heart, physiologically typical values for left ventricular myocardial deformation were obtained: the peak radial strain was approximately 40%, the peak rate of systolic wall endocardial velocity was 23 mm/s and the peak rate of diastolic wall velocity was 39 mm/s in the lateral wall. The preliminary mouse results correlate well with human MRI results.