[CCoE Notice] PhD Defense Announcement

[Khator, Suresh]

PhD Defense of Aishwarya Mantha

Hemodynamic analysis of flow near cerebral aneurysms: Insight into aneurysm formation and effects of intervention

April 10th 2012, 11:00 AM, ME Large conference room

Committee Members: Prof. Metcalfe, Prof. Kleis, Prof. Franchek, Prof Larin, Dr. Cohn and Dr. Naghavi


Abstract
The purpose of this study is to investigate the role of hemodynamics in the initiation and progression of cerebral aneurysms. It is composed of two major sections, where the first part attempts at understanding the hemodynamic cause and effect linkages leading to aneurysm formation. The second part consists of hemodynamic analysis inside the aneurysm; application of this knowledge will aid in better design of flow diverting devices.

In my Master's thesis, it was shown that low and oscillatory wall shear stresses (WSS) correlated with the aneurysm sites. In order to capture these instantaneous effects of WSS on an arterial vessel wall, a hemodynamic variable called the aneurysm formation indicator (AFI) was proposed. This work is summarized and then a careful critique of some newer aneurysm formation theories involving high WSS and wall shear stress gradients and how they relate to the AFI is presented.

Second, a numerical experiment is performed to demonstrate the potential drawbacks of using WSSG and its variations, as a hemodynamic indicator. A simple flow problem was chosen whose analytic solution is derived and compared against the numerical solution by computing WSSG in an elliptical pipe. Effects of various meshing schemes and resolutions are investigated systematically and the sensitivity of WSSG to image acquisition and reconstruction is demonstrated, along with its potential for misleading interpretation.

Third, robustness and sensitivity of the proposed AFI is demonstrated by analyzing the effects of waveform shape on the hemodynamic variables. In addition, the effects of ageing reflected by the change in waveform shape as a result of degeneration of arterial tone are also studied. It is shown that AFI indeed captures the differences in the waveforms of an older and a younger adult.

Fourth, hemodynamic influences on aneurysm stability under realistic physiological conditions are explored. Results were obtained from computational hemodynamic simulations (CHD) of six cerebral aneurysms. Two aneurysm types were considered: sidewall (paraclinoid) and bifurcation (basilar tip), with three specimens of each obtained from human patients via clinical 3D digital subtraction angiography. The goal was to identify common features of large-scale flow patterns observed in many aneurismal flows. This knowledge of flow patterns is applied towards better design of stents and other flow diverting devices. In addition, potential use of hemodynamic simulations in clinical application is also explored.


_______________________________________________________
Suresh K. Khator, Ph.D., P.E.                         Phone: 713-743-4205
Associate Dean, College of Engineering    Fax: 713-743-4214
University of Houston                                     Email: skhator at uh.edu<mailto:skhator at uh.edu>
E421 Engineering Bldg 2                                www.egr.uh.edu/ie<http://www.egr.uh.edu/ie>
Houston, TX 77204-4008

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