A Study on development of realtime system for diagnosis of regional elasticity of myocardium and arterial wall using ultrasound

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In this research, we have developed a new system to accurately measure small vibration signal on the heart wall and arterial 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 preliminary experiments herein reported, the new method offers potential for research in acoustical diagnosis of heart disease.On the other hand, this system is also applicable to the measurement of local pulse wave velosity, which is an index of the hardness in the range of several millimeters on the aortic wall. In the standard method, the pulse wave velocity (PWV) is obtained from the difference in arrival time of … More pressure waves propagating from the carotid artery to the femoral artery. In this method, the measurable points are limited to those where the aorta exists near the skin surface and the distance between such points is considerable long, i. e., several hundred millimeters. It is important for early diagnosis, however, to measure the local hardness of the surface of the arterial wall. To increase the spatial resolution, it is necessary to measure vibrations due to pulse waves with frequency components up to about 50 Hz.The developed system is also applied to measurement of local PWV by simultaneously measuring small vibrations at two points on the surface of the aortic wall. By the developed method, high spatial resolution, which is necessary in the evaluation of local hardness, is attained. By comparing the static experiments and dynamic experiments using a silicon tube, it is confirmed that the local hardness (Young's modulus) of the vessel wall is also evaluated with high spatial resolution. The local elasticity (Young's modulus) is also evaluated for each measurement point. Thus, the developed system will be effective also for local evaluation of the hardness on the aortic wall. Less