Multidimensional Heart Imaging With Ultrasound

描述(申请人提供)：舒张性功能障碍是指左心室在生理压力下充盈的能力受损，通常导致心房充盈压力的代偿性增加以维持每搏量。这种情况通常与心壁僵硬增加有关。超声心动图通过将各种测量方法与临床信息相结合，可以提供关于心脏舒张期功能的最全面的信息。下一个资助周期的目标是生产超声仪器和技术，用于定量和非侵入性、高时间和空间分辨率的活体心肌机械特性测量，特别是在体心壁的各向异性粘弹性模数测量。这种新的方法，我们称之为振动法，利用聚焦的超声束的辐射压力来刺激横波的形成和沿感兴趣区域内适当的轴线传播。剪切波的速度和频散是用脉冲多普勒、B扫描相关或我们新的卡尔曼方法测量的。波在所研究的特定几何形状中的传播的数学模型将被用来解析地求解，或者用先进的逆有限元方法来求解相关的力学特性，例如各向异性粘弹性模数。模型将通过独立的体外和体内测量进行验证。在对模体和切除的心脏的初步研究中，该方法被证明能够快速、准确和非侵入性地测量切除的心肌和横纹肌的肌纤维上和横跨肌纤维的剪切弹性(MU1)和粘性(MU2)项。这项计划的目标将通过四个具体目标来实现。目的1：在一系列日益复杂的理论发展中，我们将推导出心壁某点或某一直线上的简谐或脉冲辐射力与由此引起的附近传播波位移之间的解析数学关系。目标2：我们将使用谐波和脉冲辐射力方法来诱导运动，并使用高精度方法测量模体和组织中产生的动态应变随时间和空间的变化，以验证目标1中开发的逆解。目标3：目标1和目标2中的理论和方法将在分离的灌流跳动和非跳动心脏中进行测试。一台商用扫描仪将进行改装，以进行振动测量。目的4：振动测定法将推广到闭胸猪，以期临床应用。这项计划的成功完成将带来测量人类心壁机械特性的技术和程序，为评估与心壁僵硬变化相关的心脏异常提供了一种工具。

DESCRIPTION (provided by applicant): Diastolic dysfunction is the impaired ability of the left ventricle to fill at physiologic pressures, often resulting in a compensatory increase of atrial filling pressures to maintain the stroke volume. This condition is usually associated with increased stiffness of the heart wall. Echocardiography can provide the most comprehensive information on diastolic function of the heart by integrating a variety of measurements with the clinical information. The goals of the next grant cycle are to produce ultrasound apparatus and techniques for quantitative and noninvasive high temporal and spatial resolution biopsy-like measurement of myocardial mechanical properties, specifically the anisotropic visco-elastic moduli of the heart wall in vivo. The new method, which we call vibrometry, uses radiation pressure of a focused ultrasound beam to stimulate formation and propagation of shear waves along the appropriate axes within the region of interest. The velocity and dispersion of the shear wave is measured with pulsed Doppler, B-scan correlation, or our new Kalman method. Mathematical models for the propagation of the wave in the particular geometry being studied will be used to solve analytically or with advanced inverse finite element methods for relevant mechanical properties such as the anisotropic visco-elastic moduli. Models will be validated with independent in vitro and in vivo measurements. In preliminary investigations of phantoms and excised hearts the method has been shown to be capable of performing fast, accurate and noninvasive measurements of the elastic (mu1) and viscous (mu2) terms of the shear modulus along and across the myofibers of excised myocardium and striated muscle. The goals of this program will be achieved through four Specific Aims. Aim 1: In a sequential development of increasingly complex theories, we will derive the analytic mathematical relationships between harmonic or impulse radiation force at a point or line in the heart wall and the resulting nearby propagating wave displacements caused by the force. Aim 2: We will use harmonic and impulse radiation force methods to induce motion and high precision methods to measure the resulting dynamic strain versus time and space in phantoms and tissues to validate the inverse solutions developed in Aim 1. Aim 3: Theory and methods from Aims 1 and 2 will be tested in isolated perfused beating and non beating hearts. A commercial scanner will be modified to make vibrometry measurements. Aim 4: Vibrometry will be extended to closed chest pigs in anticipation of clinical application. Successful completion of this program will result in techniques and procedures for measuring mechanical heart wall properties in humans providing a tool for evaluating cardiac abnormalities associated with alterations in heart wall stiffness.