TECHNICAL PAPERS: Fluids/Heat/Transport

Validation of CFD Simulations of Cerebral Aneurysms With Implication of Geometric Variations

[+] Author and Article Information
Yiemeng Hoi, Scott H. Woodward, Minsuok Kim

Department of Mechanical and Aerospace Engineering, University at Buffalo, Buffalo, NY 14260 and Toshiba Stroke Research Center, University at Buffalo, Buffalo, NY 14260

Dale B. Taulbee

Department of Mechanical and Aerospace Engineering, University at Buffalo, Buffalo, NY 14260

Hui Meng

Department of Mechanical and Aerospace Engineering, University at Buffalo, Buffalo, NY 14260; Toshiba Stroke Research Center, University at Buffalo, Buffalo, NY 14260; and Department of Neurosurgery, University at Buffalo, Buffalo, NY 14260huimeng@eng.buffalo.edu

J Biomech Eng 128(6), 844-851 (Jun 15, 2006) (8 pages) doi:10.1115/1.2354209 History: Received September 27, 2005; Revised June 15, 2006

Background. Computational fluid dynamics (CFD) simulations using medical-image-based anatomical vascular geometry are now gaining clinical relevance. This study aimed at validating the CFD methodology for studying cerebral aneurysms by using particle image velocimetry (PIV) measurements, with a focus on the effects of small geometric variations in aneurysm models on the flow dynamics obtained with CFD. Method of Approach. An experimental phantom was fabricated out of silicone elastomer to best mimic a spherical aneurysm model. PIV measurements were obtained from the phantom and compared with the CFD results from an ideal spherical aneurysm model (S1). These measurements were also compared with CFD results, based on the geometry reconstructed from three-dimensional images of the experimental phantom. We further performed CFD analysis on two geometric variations, S2 and S3, of the phantom to investigate the effects of small geometric variations on the aneurysmal flow field. Results. We found poor agreement between the CFD results from the ideal spherical aneurysm model and the PIV measurements from the phantom, including inconsistent secondary flow patterns. The CFD results based on the actual phantom geometry, however, matched well with the PIV measurements. CFD of models S2 and S3 produced qualitatively similar flow fields to that of the phantom but quantitatively significant changes in key hemodynamic parameters such as vorticity, positive circulation, and wall shear stress. Conclusion. CFD simulation results can closely match experimental measurements as long as both are performed on the same model geometry. Small geometric variations on the aneurysm model can significantly alter the flow-field and key hemodynamic parameters. Since medical images are subjected to geometric uncertainties, image-based patient-specific CFD results must be carefully scrutinized before providing clinical feedback.

Copyright © 2006 by American Society of Mechanical Engineers
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Figure 4

In-plane vorticity contours and positive circulation values in (a) Plane A, (b) Plane B, and (c) Plane C for various models. (Solid lines represent positive vortex; dashed lines represent negative vortex).

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Figure 5

(a)–(c) Variations of magnitude of vertical velocity component in Plane Z, along three horizontal lines, marked as A, B, and C, obtained from intersection with Planes A, B, and C

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Figure 1

Geometry of the experimental phantom. A, B, C, and Z denote the PIV imaging planes. Plane Z is the meridian plane. Plane A is 0.25d below the center of the aneurysm. Plane B is at the center of the aneurysm, and Plane C is 0.25d above the center of aneurysm, where d is the major diameter.

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Figure 2

Schematic diagram of the experimental setup, with Plane B being imaged. Imaging Planes A and C required parallel shifts of the laser light sheet, and imaging Plane Z required turning the model block 90° so that the meridian plane faced the camera.

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Figure 3

Comparison of (a) velocity fields in Plane Z, (b) velocity fields, and (c) vorticity contours in Plane B for various models




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