Imaging spatial distribution of high-frequency small vibrations on the heart wall

We have developed a novel method for accurately measuring the velocity signals on the multiple points preset on an ultrasonic beam in the heart wall by tracking the movement of the heart wall. By applying the time-frequency analysis to the resultant velocity signals of the heart wall, we have determined the instantaneous eigenfrequency of the left ventricle (LV) at the end-diastole. From the eigenfrequency, the wall thickness of the LV, the average radius of the LV, and the inner pressure of the LV, are noninvasively estimated at the end-diastole using a model of an elastic spherical shell. For this measurement, however, it is necessary to confirm the mode of the eigenvibration in the LV. In this report, therefore, we control the directions of the ultrasonic beams so that the velocity signals are simultaneously measured at the multiple points on the surface of the LV wall. From these data, we estimate the spatial distribution of the eigenvibration of the LV wall at the end-diastole.