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

摘要建议编号：CTS-0421461首席研究员：R.Shandas，美国科罗拉多大学不透明流体流动速度场的测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渲染的复杂形状的流动的成像，到充气冲浪区流动的严格限制。在心血管研究方面，对生物进行测量的额外要求进一步限制了流场仪器的选择和能力。这笔赠款是为了开发一种系统，以满足这些需求，基于两项现有技术的综合：粒子图像测速(PIV)和亮度模式(B模式)对比超声回波成像：ECHO PIV。医用B型对比回声成像是通过“造影剂”的超声后向散射实现的，造影剂是注入血流的薄层气体微泡。然后对两个序列图像进行PIV分析，其中两个图像之间的互相关给出粒子的位移，从而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以满足科罗拉多大学(CU)目前的心血管流体动力学研究计划。超声技术的进步是必要的，但也是可行的。该系统将用于支持UCHSC的一系列心血管血流研究。特别是，该系统将能够测量小动脉壁附近的流体剪切，回答了许多关于剪切在血管疾病中的作用的问题。它将能够测量大血管系统中复杂的、依赖于时间的流动，例如活体的主肺动脉和主动脉弓，允许验证寻求将壁面的真实固体力学模型与脉动3-d流动相结合的建模努力。它还将用于增加对脑室血流的了解，在这种情况下，基于流体物理的分析可能导致区分因年龄而引起的变化与因疾病而引起的变化。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。PIs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：这两个组合确保了广泛的研究生和本科生参与这一系统的发展。此外，这个系统将被用作新生和研究生设计课程的范例。

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.