A Study on Ultrasonic Measurement and Visualization of Propagation of Myocardial Contraction Response

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For realization of non-invasive regional myocardial tissue characterization, in the present study, we tried to elucidate the characteristic of the myocardial response to the electrical excitation by an in vitro experiment using an excised rat left-ventricular wall. To visualize such propagation phenomenon, whose propagation speed is up to several m/s, high frame rate ultrasound was used. Propagation of the myocardial vibration was visualized by estimating the delay time between vibration waveforms measured in the reference ultrasonic beam and each ultrasonic beam using the cross-correlation function between the vibration waveforms. From the estimated delay time, we visualized the propagation of myocardial vibration caused by the electrical excitation. Propagation velocities were estimated to be 2.5 m/s at the internal and external surfaces of the left-ventricular wall. These results correspond to the results obtained in in vivo experiments measured with high frame rate ultrasound.