High resolution 2D quantification of myocardial motion abnormalities in mice using high resolution ultrasound with MRI validation

High resolution ultrasound image sequences of left-ventricular motion abnormalities in mice were analyzed on a regional basis using an optimized 2D pixel block tracking technique. The mouse heart was imaged at 35 MHz with approximately 40 mum axial resolution and 100 mum lateral resolution. Myocardial regional motion was tracked using high frame rate mouse heart image sequences using 2D minimum sum of absolute differences (MSAD) block matching. Eight pixel parallel processing was achieved using single instruction multiple data (SIMD) instructions, resulting in a processing speed of 0.11 seconds per frame on a 2.9 GHz Pentium4 PC. Significant differences were observed in the regional displacement, strain and velocity between healthy and infarcted myocardial tissue. Myocardial strains were compared to those obtained via magnetic resonance imaging (MRI). The correlation between the assessment using ultrasound and MRI was R = 91% for radial strain and R = 84% for circumferential strain. Thus, high resolution ultrasound followed by 2D image motion post-processing offers the potential to derive quantitative measures of mouse heart function with the low cost, fine temporal resolution and ease-of-mobility of ultrasound instrumentation