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

为了实现无创的局部心肌组织表征，本研究通过切除大鼠左室壁的体外实验，试图阐明心肌对电刺激的反应特征。为了使这种传播速度可达数m/s的传播现象可视化，采用了高帧率超声。利用振动波形间的互相关函数估计参考超声波束中测量到的振动波形与各超声波束之间的延迟时间，从而可视化心肌振动的传播过程。根据估计的延迟时间，我们可视化了由电激励引起的心肌振动的传播。左室壁内外表面的传播速度估计为2.5 m/s。这些结果与高帧率超声在体内实验中得到的结果相一致。

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.