Graduate Seminar in Fluid Mechanics
4:10-4:35 p.m. Presentation
“Echo Contrast Particle Image Velocimetry in Brain and Heart”
Presented by ZENG ZHANG (Adviser: Prof. Katz)
Quantitative assessment of hemodynamic flows is vital for clinical diagnostics, especially in cardiology and neurology. Routinely, MRI or ultrasound doppler imaging are used to obtain such data. However, doppler imaging is limited to a single point, and MRI is not suitable for certain patients e.g. those requiring life-support equipment. Therefore, our objective is to develop a convenient tool combining contrast ultrasound imaging, which is a widely used clinical tool, with particle image velocimetry to obtain real-time blood velocity maps in internal organs that will be available during routine clinical tests. This technique is referred to as Echo contrast Particle Image Velocimetry (Echo-PIV). Unlike optical PIV, echo images are prone to non-uniform spatiotemporal variations in tracer distribution, complicating the application of standard PIV algorithms. To address this problem, our group has developed an optimized procedure that integrates image enhancement, PIV and particle tracking velocimetry (PTV) to obtain reliable time-resolved 2D velocity distributions (Sampath et al., 2018). It has been used successfully for studying the flow inside a human’s left ventricle. For this presentation, this procedure is being implemented in two studies: (i) Characterizing the flow inside a neonatal brain in cases with suspected brain injury. New image segmentation procedures involving a support vector machine (SVM) with multiple criteria have been developed for distinguishing between blood vessels and background in the brain images, enabling detection of blood flow in narrow passages. (ii) Measuring the interaction between cardiac flow and the flow induced by an external ECMO machine which is designed to oxygenate blood in patients with non-functioning heart or lung. On-going tests show the evolution of the aortic root flow in pigs as the ECMO flow impinges on the cardiac output during the cardiac cycle.