Simultaneous measurement of the structure and function of the artery using an intravascular ultrasound transducer.

我们研究了血管内超声技术，同时测量结构，弹性和血流相对于动脉。我们测量了动脉壁的声学特性，如声速、声阻抗和壁的反射率，因为即使这些对于动脉的超声测量是必要的，也不能充分获得。利用射频回波信号的频谱分析，成功地测定了动脉壁等薄层的声速。在声阻抗方面，血管壁与血液之间的差异仅为1%左右。这导致了即使阻抗变化相对较小，反射率的变化也很大。然后，我们开发了一种血管内超声成像系统，用于测量动脉的结构和弹性。从其横截面图像获得动脉的管腔面积的脉动变化，并用于确定弹性。为了提高测量精度，根据管腔面积与血压的回归线的斜率计算弹性。弹性测量与发达的方法沿着狗主动脉显示出相当的准确性与参考方法，这是专门设计的弹性measurement.In除了上述测量，我们从理论和实验上研究了一种新的技术，用于测量流量垂直于轴的超声波束与一个单一的换能器。利用这种技术，我们可以测量流量，而无需额外的传感器进行速度测量。当RF回波信号以一定的重复率获取时，横向分量可以从相关性的峰值确定。我们进行了实验，以验证我们的方法的有效性，使用多孔体模放置在转台和流动的淀粉悬浮液在水中的管。实验结果与理论分析吻合较好。

We studied intravascular ultrasound techniques for simultaneous measurements of structure, elasticity and blood flow with respect to the artery. The following results were obtainedWe measured the acoustic properties of arterial walls such as sound velocity, acoustic impedance and reflectivity of the wall, because these were not sufficiently available even if essential for ultrasonic measurement of the artery. The sound velocity of a thin layr like an arterial wall was successfully determined using a spectrum analysis of RF echo signals. As for acoustic impedance there was only abount 1% difference between the wall and the blood. This resulted in large variation of the reflectivity even if the impedance change was relatively small.We then developed an intravascular ultrasound imaging system for the measurement of both the structure and elasticity of the artery. Pulsatile change in luminal area of the artery was obtained from its cross-sectional images and used for determining the elasticity. To improve the measurement accuracy, the elasticity was calculated from the slope of a regression line of luminal area to blood pressure. Elasticity measurement with the developed method along the dog aorta showed comparable accuracy with a reference method which was specially designed for elasticity measurement.In addition to the above measurements, we theoretically and experimentally studied a new technique for measuring a flow perpendicular to the axis of an ultrasound beam with a single transducer. With this technique we can measure a flow rate without additional transducer for velocity measurement. When RF echo signals are taken at a certain repetition rate, the transverse component can be determined from the peak value of the correlation. We conducted experiments to verify the validity of our method, using porous phantom placed on a turn table and flow of starch suspension in water within a tube. Experimental results agreed well with theoreticals.