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Research Papers

Numerical Simulation of Pre- and Postsurgical Flow in a Giant Basilar Aneurysm

[+] Author and Article Information
Vitaliy L. Rayz

 Radiology Service, VA Medical Center-San Francisco, 4150 Clement Street, San Francisco, CA 94121vlrayz@gmail.com

Michael T. Lawton

 UCSF Center for Cerebrovascular Research, 1001 Potrero Avenue, San Francisco, CA 94110lawtonm@neurosurg.ucsf.edu

Alastair J. Martin

Department of Radiology, University of California San Francisco, 505 Parnassus Avenue, San Francisco, CA 94143amartin@radiology.ucsf.edu

William L. Young

James P. Livingston Professor Vice-Chair of Department of Anesthesia and Perioperative Care Professor of Neurological Surgery and Neurology University of California San Francisco, 1001 Potrero Avenue, San Francisco, CA 94110youngw@anesthesia.ucsf.edu

David Saloner

Department of Radiology, University of California San Francisco, San Francisco CA 9443; Director Vascular Imaging Research Center, VA Medical Center-San Francisco, 4150 Clement Street, San Francisco, CA 94121saloner@radmail.ucsf.edu

J Biomech Eng 130(2), 021004 (Mar 27, 2008) (6 pages) doi:10.1115/1.2898833 History: Received October 17, 2006; Revised September 12, 2007; Published March 27, 2008

Computational modeling of the flow in cerebral aneurysms is an evolving technique that may play an important role in surgical planning. In this study, we simulated the flow in a giant basilar aneurysm before and after surgical takedown of one vertebral artery. Patient-specific geometry and flowrates obtained from magnetic resonance (MR) angiography and velocimetry were used to simulate the flow prior to and after the surgery. Numerical solutions for steady and pulsatile flows were obtained. Highly three-dimensional flows, with strong secondary flows, were computed in the aneurysm in the presurgical and postsurgical conditions. The computational results predicted that occlusion of a vertebral artery would result in a significant increase of the slow flow region formed in the bulge of the aneurysm, where increased particle residence time and velocities lower than 2.5cms were computed. The region of slow flow was found to have filled with thrombus following surgery. Predictions of numerical simulation methods are consistent with the observed outcome following surgical treatment of an aneurysm. The study demonstrates that computational models may provide hypotheses to test in future studies, and might offer guidance for the interventional treatment of cerebral aneurysms.

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Copyright © 2008 by American Society of Mechanical Engineers
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Figures

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Figure 2

Coregistration of the presurgical (gray) and postsurgical (black) geometries

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Figure 3

Presurgical flow streamlines for the flow entering (a) through the left vertebral and (b) through the right vertebral

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Figure 4

(a) Presurgical (top row) and postsurgical (bottom row) flow streamlines, (b) velocity magnitude distribution, and (c) particle residence time for steady flow simulations

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Figure 5

Number of particles remaining at a given time in the aneurysm for presurgical and postsurgical flows

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Figure 6

Surfaces of constant velocity (2.5cm∕s) at different times of the cardiac cycle for presurgical (top row) and postsurgical (bottom row) flows

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Figure 7

WSS distribution at different times of the cardiac cycle for presurgical (top row) and postsurgical (bottom row) flows

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Figure 8

Coregistration of presurgical and postsurgical geometries with a constant velocity surface obtained from CFD simulation. Three views of the coregistered geometries are shown to demonstrate the three-dimensional distribution of the thrombus. Gray is the original lumen, blue is the postsurgical lumen, and red is the CFD constant velocity surface.

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Figure 1

CE-MRA data: (a) giant basilar aneurysm presenting with rapid growth before surgery and (b) after clipping of the right vertebral artery. Arrow 1 shows the clip location on the right vertebral artery; Arrow 2 points at the bypass connecting the clipped vertebral to the superior cerebral artery (note that the remainder of the bypass lies outside the imaging volume and is not visualized).

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