| Research Abstract |
Myocardial motion exhibits frequency components of up to 100 Hertz as found by a phased tracking method. To simultaneously measure the rapid and minute velocity signals at multiple points along the surface of the left ventricle (LV), in this study, conventional ultrasonic diagnosis equipment was modified to allow 10 scan lines from a sector scanner to be arbitrarily selected in real time for analysis. By considering the maximum value of the velocity in the heart wall and the maximum depth from the chest surface, the number of transmission directions of the ultrasonic pulses should be carefully confirmed to be 10 to avoid aliasing, which is much less than the number employed in conventional tissue Doppler imaging (TDI). By applying the system, the velocity signals at about 240 points in the heart walls were simultaneously measured for three healthy volunteers. During a short period of 35 ms around end-diastole, the velocity signals varied spatially in the heart wall. At the end of systo
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le, in the wavelets near the base of the interventricular septum (IVS), the slow pulse continued for about 30 ms just before the radiation timing of the second heart sound. Then, a steep pulse occurred just at the timing of the closure of the aortic valve. The steep pulse at the base preceded that at the apex by several milliseconds. By Fourier transforming each wavelet, the spatial distribution of the phase of the steep pulsive components were clearly displayed. By applying the measurement method to two patients with aortic stenosis (AS) , irregular vibration signals, which correspond to the murmur of the heart sound, could be directly detected during ejection period. In conventional TDI, only the large slow movements due to the heartbeat are displayed, while these rapid and minute velocity components cannot be displayed. In this study, moreover, the phase components were detected for the first time from each of the velocity signals simultaneously measured at multiple points along the 10 scan lines. This measurement and method of analysis offer potential for new diagnostic techniques in cardiac dysfunction. Less
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