Arterial Properties from Stimulated Acoustical Emission

描述(由申请人提供)： 大血管和传导动脉僵硬的增加最近被认为是心血管和许多其他疾病的潜在危险因素。评估人体血管硬度的标准方法测量血管直径的变化，并将这些测量与动脉压联系起来，以估计动脉硬度(顺应性)。这项技术可能很耗时，在与血管张力快速变化相关的生理动作中很难应用，而且对于几种派生的僵硬计算中哪一种是最好的存在争议。此外，非侵入性的血压测量可能会在估计动脉硬度时带来额外的误差。因此，开发评估人类血管僵硬的新方法有可能成为研究健康和疾病中人类心血管功能的一种非常有用的工具。这里提出的方法的优点是它们是非侵入性的，并且允许对特性进行实时测量，并且它们考虑到特性是频率的函数的事实。我们的新方法是我们的振动声学技术的延伸。我们使用聚焦超声束的辐射压力在一组低频(50-600赫兹)上振动容器的壁。然后，我们测量每个频率在血管壁内传播的剪切波的速度和衰减。然后根据色散曲线计算杨氏模数。这项应用的目标是开发这种非侵入性的方法来定量测量血管的材料特性。我们将通过四个具体目标来实现这些目标：1)扩展先进的血管壁剪切波和波声发射的波传播理论，2)开发更好的用于诱导组织运动的换能器和用于测量由此产生的声发射和位移的接收器，3)在动物身上验证我们新开发的振动测量方法，以及4)将振动测量方法应用于定量测量人类血管壁粘弹性(复数杨氏模数)。这项计划的成功完成将带来新的非侵入性方法来评估动脉僵硬和其他材料特性，适用于有意识的人的快速和准确的测量。

DESCRIPTION (provided by applicant): Increased stiffness of the great vessels and conducting arteries has recently gained acceptance as a potential risk factor for cardiovascular and many other diseases. Standard methods for estimating blood vessel stiffness in humans measure changes in blood vessel diameter and relate these measurements to arterial pressure to estimate arterial stiffness (compliance). This technique can be time-consuming, is difficult to apply during physiologic maneuvers associated with rapid changes in blood vessel tone, and there is controversy about which of several derived calculations of stiffness is best. In addition, non-invasive determination of blood pressure may bring additional errors in the estimation of arterial stiffness. Therefore, development of new approaches to assess blood vessel stiffness in humans has the potential to be an extremely useful tool in studying human cardiovascular function in health and disease. The advantages of the methods proposed here are that they are noninvasive and fast allowing real-time measurement of properties, and they take into account the fact that properties are a function of frequency. Our new method is an extension of our vibro-acoustography technique. We use radiation pressure of focused ultrasound beams to vibrate the wall of a vessel at a set of low frequencies (50-600 Hz). We then measure the speed and attenuation of the resulting propagating shear wave within the vessel wall for each frequency. The Young's modulus is then calculated from the dispersion curves. The goal of this application is to develop this noninvasive method for quantitatively measuring the material properties of vessels. We will achieve these goals with four specific aims including: 1) Extended development of advanced wave propagation theory for shear waves in walls of vessels and for acoustic emission from the waves, 2) Development of better transducers for inducing tissue motion and receivers for measuring the resulting acoustic emission and displacement, 3) Validation of our newly developed vibrometry methods in animals, and 4) Application of vibrometry methods to quantitative measurement of vessel wall viscoelasticity (complex Young's modulus) in humans. Successful completion of this program will result in new noninvasive methods to assess arterial stiffness and other material properties with fast and accurate measurements applicable to the conscious human.