"Development of system for measurement and analysis of small vibration on heart wall for early stage diagnosis of myocardium"

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In this research, we have developed a new system to accurately measure small vibration signal on the heart wall. By this method, small vibrations of the heart wall with small amplitudes less than 100 mum on the motion resulting from a heartbeat with large amplitude of 10 mm can be successfully detected with sufficient reproducibility in the frequency range up to several hundred Hertz continuously for periods of about ten heartbeats. The resultant small vibration is analyzed not only in the time domain but also in the frequency domain. As confirmed by the experiments herein reported, the new method offers potential for research in acoustical diagnosis of heart disease.In this research, the method is applied to multiple points preset in the left ventricular (LV) wall along the ultrasonic beam so that the spatial (depth) distributions of the velocity at these points are simultaneously obtained. The motion of the heart wall is divided into the following two components : parallel global motion of the heart wall and the change in myocardial layr thickening at each depth across the LV wall during myocardial contraction/relaxation. The latter component is superimposed on the M (motion) -mode image using a color code to map contraction as red and expansion as blue. By preliminary human studies, the principle of the method proposed in this paper is verified and the frequency band of the components generated by thickening and/or thinning in the myocardium is identified. This new approach offers potential for research on noninvasive acoustical diagnosis of myocardial local motility, that is, the myocardial layr function at each depth in the ventricular wall.