"Development of ultrasonic diagnosis system for early-stage arteriosclerosis using impulsive actuator"

在这项研究中，我们开发了一种新的方法来测量局部脉搏波速度，这是一个衡量主动脉壁几毫米范围内硬度的指标。在标准方法中，脉搏波速度(PWV)是由压力波从颈动脉传播到股动脉的到达时间之差得到的。在这种方法中，可测量的点仅限于主动脉位于皮肤表面附近，并且这些点之间的距离相当长，即数百毫米。然而，测量动脉壁表面的局部硬度对于早期诊断很重要。为了提高空间分辨率，需要测量频率高达50赫兹的脉搏波引起的振动，因此，我们开发了一种新的系统，基于超声多普勒效应，从皮肤表面非侵入性地测量心脏或主动脉壁上的微小振动信号。该系统从胸腔起连续10多个搏动周期，在1 kHz以下的频率范围内，成功地检测到幅度为10~100微米的微小振动，幅度为10 mm。为了提高动脉壁振动局部速度测量的空间分辨率，本研究还开发了一种新的方法，从脊椎向外激励频率高达1 kHz的脉冲波，并经皮测量脉冲波在主动脉壁上传播的两个近似点的传播延迟时间。该方法为动脉硬化的声学诊断研究提供了潜力。

In this research, we have developed a new method to measure local pulse wave velocity, 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 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.Therefore, we have developed a new system to noninvasively measure small vibration signals on the heart wall or the aortic wall from the surface of the skin based on the ultrasonic Doppler effect. By this system, small vibrations with amplitudes of 10-100mum on the motion due to heart beat with the large amplitude of 10 mm are successfully detected in the frequency range up to 1 kHz continuously for more than ten beat periods from the chest.To improve the spatial resolution in the local velocity measurement of vibration propagating on the arterial wall, this research also developed a new method to actuate impulsive wave with higher frequency components until 1 kHz from the backbone and transcutaneously measure the transit delay time of the impulsive wave propagating two proximate points on the aortic wall. The method offers potential for research in acoustical diagnosis of arteriosclerosis.