MRI: Development of a Micro- and Macro- particle Image Velocimetry System for Opaque Flows

摘要建议编号 CTS-0421461主要研究者： R.不透明流体流的速度场的确定在流体研究的许多领域都是一个挑战，从难以在透明介质中呈现的复杂形状的流动的成像，到充气冲浪区中流动的苛刻限制。在心血管研究的背景下，在活体中进行测量的附加要求进一步限制了流场仪器的选择和能力。这项资助是为了开发一个系统，以满足这些需求，基于两个现有的技术，粒子图像测速（PIV）和清晰度模式（B模式）对比超声回波成像：回声PIV的合成。 医用B型造影回波成像是通过超声从“造影剂”，薄壳的微气泡，已被注射到血流中的反向散射来实现的。然后对两个连续图像进行PIV分析，其中两个图像之间的互相关给出了颗粒的位移，允许基于图像之间的时间来确定速度矢量场。一个原型系统目前正在使用中，但现成的组件导致空间分辨率和动态范围不足的心血管流体动力学在科罗拉多大学（CU）的当前研究计划。超声技术的进步将是必要的，但是可行的。该系统将用于支持UCHSC的一系列心血管流量研究。特别是，该系统将能够测量小动脉壁附近的流体剪切力，回答有关剪切力在血管疾病中的作用的许多问题。它将能够测量复杂的，时间依赖性的大型脉管系统，如主肺动脉和主动脉弓在体内的流量，允许验证建模努力，寻求结合联合收割机现实的固体力学模型的墙壁与脉动的3-d流。它还将用于增加对心室流量的理解，其中基于流体物理学的分析可能导致区分因年龄引起的变化和因疾病引起的变化。这项工作将通过演讲和出版物传播到生物医学和实验流体动力学社区。PI是NIH培训补助金的接受者，科罗拉多大学是促进生物医学研究中代表性不足群体的补助金的接受者：这一组合确保了广泛的研究生和本科生参与该系统的开发。此外，这个系统将被用作新生和研究生设计课程的例子。

ABSTRACTProposal No. CTS-0421461Principal Investigator: R. Shandas, University of ColoradoDetermination of the velocity field of opaque fluid flows is a challenge in many areas of fluids research, ranging from the imaging of flows in complex shapes that are difficult to render in transparent media, to the demanding constraints of flow in the aerated surf zone. In the context f cardiovascular research, the added requirements of measurements made in living creatures limit the choices and capabilities of flow field instrumentation even further. This grant is to develop a system to meet these needs, based on the synthesis of two existing technologies, Particle Image Velocimetry (PIV) and Brightness-Mode (B-mode) contrast ultrasound echo imaging: Echo PIV. Medical B-mode contrast echo imaging is achieved by the backscatter of ultrasound from "contrast agent", thin-shelled microbubbles of gas that have been injected into the bloodstream. Two sequential images are then subjected to PIV analysis, in which a cross correlation between the two images gives the displacement of the particles, allowing a velocity vector field to be determined based on the time between images. A prototype system is currently in use, but the off-the-shelf components result in spatial resolution and dynamic range inadequate for the current research program in cardiovascular fluid dynamics at the University of Colorado (CU). Advances in ultrasound technology will be required, but are feasible. This system will be used in support of a range of studies of cardiovascular flow at UCHSC. In particular, this system will enable the measurement of fluid shear near the walls of small arteries, answering many questions about the role of shear in vascular diseases. It will enable the measurement of the complex, time dependent flows in the large vasculature, such as the main pulmonary artery and aortic arch in vivo, allowing the validation of modeling efforts that seek to combine realistic solid mechanics models of the walls with pulsatile 3-d flows. It will also be used to increase understanding of ventricular flows, where fluid-physics-based analysis may lead to the differentiation of changes due to age from those due to illness. This work will be disseminated into both the biomedical and experimental fluid dynamics communities via presentations and publications. The PIs are recipients of an NIH training grant, and University of Colorado is the recipient of a grant promoting underrepresented groups in biomedical research: the combination ensures the participation of a wide range of graduate and undergraduate students in the development of this system. Also, this system will be used as examples in both freshman and graduate design courses.