Measurement of high velocity distribution of the myocardium

Abstract

The heart wall motion is color-coded and displayed by the conventional tissue Doppler imaging (TDI) technique. Myocardial motion, however, exhibits frequency components of at least up to 100 Hertz as found by a phased tracking method. In TDI, only the strong slow movements due to the heartbeat are displayed while the rapid and minute velocity components are not included in the results. In this study, by considering the maximum value of the velocity at the points in the interventricular septum (IVS) or the left-ventricle posterior wall (LV-PW) of the human heart, the number of transmission directions of the ultrasonic pulses should be confirmed to be 10, which is much less than the number employed in TDI. Ultrasonic diagnosis equipment was modified so that the 10 directions of the ultrasonic beams were controlled in real time using a micro-computer. By applying the system, the velocity signals at about 240 points in the IVS and the LV-PW were simultaneously measured for healthy volunteers. During a short period of 35 ms around the end diastole, the velocity signals varied spatially in the heart wall. By applying the method to a patient with aortic stenosis (AS), irregular vibration signals, which correspond to the murmur, can be directly detected. This method offers potential for new diagnostic techniques in cardiac dysfunction.