Arterial Properties from Stimulated Acoustical Emission

描述（由申请人提供）： 最近，大血管和传导动脉的僵硬度增加被认为是心血管和许多其他疾病的潜在危险因素。用于估计人体血管硬度的标准方法测量血管直径的变化，并将这些测量结果与动脉压相关联，以估计动脉硬度（顺应性）。这种技术可能是耗时的，很难应用在与血管张力的快速变化相关的生理演习期间，并且对于几种刚度的推导计算中哪一种是最好的存在争议。此外，血压的无创测定可能在动脉硬度的估计中带来额外的误差。因此，开发新的方法来评估人体血管硬度有可能成为研究健康和疾病中人类心血管功能的非常有用的工具。这里提出的方法的优点是，它们是非侵入性的和快速的，允许实时测量的属性，并且它们考虑到属性是频率的函数的事实。我们的新方法是我们的振动声成像技术的扩展。我们使用聚焦超声波束的辐射压力以一组低频（50-600 Hz）振动血管壁。然后，我们测量每个频率的血管壁内产生的传播剪切波的速度和衰减。然后从色散曲线计算杨氏模量。本申请的目的是开发这种非侵入性方法，用于定量测量血管的材料特性。我们将通过四个具体目标实现这些目标，包括：1）扩展发展先进的波传播理论，用于血管壁中的剪切波和来自波的声发射，2）开发用于诱导组织运动的更好的换能器和用于测量所产生的声发射和位移的接收器，3）验证我们新开发的动物振动测量方法，和4）应用振动测量法定量测量人体血管壁粘弹性（复杨氏模量）。该项目的成功完成将导致新的非侵入性方法，以评估动脉硬度和其他材料特性，快速，准确的测量适用于有意识的人。

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.