Computational and Experimental Hemodynamic Analysis of an Intracranial Aneurysms

Abstract

Hemodynamics is thought to play a fundamental role in the mechanisms of cerebral aneurysm formation, growth, and either stabilization or rupture. Understanding these mechanisms is important to improve current diagnosis and treatment of intracranial aneurysms. The purpose of this study was to analyze the blood flow field in a growing cerebral aneurysm using experimental particle image velocimetry (PIV) and computational fluid dynamics (CFD) techniques. Patient-specific models were constructed from 3D computed tomography angiography (CTA) images acquired at one-year intervals during a conservative follow up period. Physical silicone models were constructed from the CTA images using rapid prototyping techniques and the pulsatile blood flow fields were measured with PIV. Corresponding CFD models were created and run under pulsatile flows matching the experimental flow conditions. For comparison, the PIV and CFD models were aligned and the corresponding flow fields interpolated to a common grid covering the aneurysm volume. The blood flow fields were then visualized and compared qualitatively by inspection and quantitatively by defining a similarity measure between the PIV and CFD vector fields. The results indicate that the experimental and computational flow fields are in good agreement. Specifically, both techniques yield consistent qualitative representations of the major characteristics of the inflow stream and the intra-aneurysmal flow structures, and their change during the geometric evolution of the aneurysm. Additionally, the PIV and CFD flow fields exhibit a degree of coincidence of over 80% in the aneurysm interior. However, as expected, differences between the experimental and computational results were observed in the regions near the aneurysm wall. Differences in the magnitudes of the CFD and PIV velocities were also observed. Possibly, these differences could be attributed to the limited resolution of the experimental measurements and to imperfect match of the flow boundary conditions. Despite these differences and the inherent limitations of both techniques, the information derived from these complementary models is consistent and can be used to study the role of hemodynamics in the mechanisms of aneurysm pathogenesis and progression.