CFD & AMP Center
Department of Mechanical & Aerospace Engineering
West Virginia University
E: ismail.celik@mail.wvu.edu

CFD Simulation of Flow Through an Intracranial Aneurysm

Title
CFD Simulation of Flow Through an Intracranial Aneurysm
 
Sponsor
WVU Research Corporation
 
Investigators
Dr. Ismail B. Celik (PI)
Dr. Jaggu Nanduri (Co-PI)
Francisco Adolfo Pino Romainville (Graduate Student)
 
Collaborators
Dr. Anssar Rai, MD (Neurosurgery)
 

Abstract

The formation and growth of intracranial aneurysms is partly attributed to various hemodynamic factors such as shear stress and pressure. This issue is further investigated in the current study using some new insight gained from passive scalar dispersion in the blood flow. Intracranial aneurysms are best visualized using selective catheter angiogram technique where a contrast agent added to the blood flow is visualized and filmed dynamically. In the current study, the 2D threshold images produced by “3D rotational X-ray angiography technique” are used in an ‘in-house’ program to construct a 3D volumetric grid which is then used to calculate the blood flow through the aneurysm. Dispersion of a fluid material with properties similar to that of the contrast agent is also modeled in the blood flow. We investigated the dispersion of a pulsed scalar to better understand the flow dynamics. Results from a large aneurysm are compared to those for a relative small one to show the effect of geometry. The dispersion and flow patterns show the localization of high stress in stagnation areas, which may be the potential regions for the origin and growth of aneurysms. We also investigated the dependence of flow properties on the initial and boundary conditions along with an estimate of the discretization error and uncertainity in CFD studies for biofluids applications such as this.

Methodology

Image Acquisition

An X-ray angiogram was performed to a 66-year-old female who presented a giant intracranial aneurysm. Using rotational arm constructed by Siemens, the images were obtained and recorded in four sets of 100 pictures each. The 2D monochromatic images were obtained using the Leonardo software which also computes a 3D visualization of the aneurysm. A nonionic diametric contrast medium (Visipaque Iodixanol 320mgI/mL) was injected during angiography to record the lumen of the arteries.

Model Reconstruction

The rotational angiogram produced images of resolution 512x512 pixels and the slice distance among each image was 0.213158 mm. These images were processed through MATLAB (Mathworks Inc., Natick, MA) to capture the vessel boundaries and generate an iso-surface based on the threshold of the image. Image processing functions similar to those documented in [17] were used to enhance and cleanup the geometry before iso-surface extraction. A region of interest was captured by eliminating the outlying arteries and retaining the main artery, the aneurysm and the bifurcating arterial branch downstream of the aneurysm. Inlets and outlet(s) cross-sections were cut to include the “twist and bend” in the artery leading to the aneurysm and the two bifurcation branches after the aneurysm. In order to make the outlet cross-sections perpendicular to the flow direction, 3Matic software (Materialise, Leuven, Belgium) was used. For more information see CFD Model reconsturuction from diagnostic images- Nanduri et al., Computers and Fluids, 38 (2009), 1026-1032

           

Angiography procedure showing aneurysm   Angiography machine generated image   CFD geometry created from diagnostic images

CFD Simulation

For details on the simulations and results please see

Pino-Romainville, F. A ,Nanduri, J. R.,Celik I. B. and Rai, A. T., "Dispersion Study in a Giant Intracranial Aneurysm using Computational Fluid Dynamics Techniques", Proceedings of 5th Joint ASME/JSME Fluid Engineering Summer Conference, July 30-August 2, 2007, San Diego, CA, USA, FEDSM2007-37444

Pino-Romainville, F. A., Nanduri, J. R. , Celik, I. B. and Rai, A. T., "Quantification of Discretization Error in Wall Shear Stress Calculations for Aneurismal Flows Using CFD", To be presented at ASME Fluid Engineering Division Summer Conference, August 10-14, (2008), Jacksonville, Florida, USA

Rai, A. T., Nanduri, J. R. , Pino-Romainville F. A., and Celik, I. B., "Computational Fluid Dynamics I - Towards Creating an Accurate Aneurysm Geometry for Flow Analysis: Internal Flow Meshes from Rotational Angiography", Poster presented at 4th Annual ASITN (American Society of Interventional and Therapeutic Neuroradiology) Course and Workshops, July 30 - August 3, (2007), Dana Point, CA

Rai, A. T., Nanduri, J. R. , Pino-Romainville F. A., and Celik, I. B., "Computational Fluid Dynamics II - Impact of Aneurysm Geometry on Aneurysm Hemodynamics ", Poster presented at 4th Annual ASITN (American Society of Interventional and Therapeutic Neuroradiology) Course and Workshops, July 30 - August 3, (2007) Dana Point, CA, USA