Eventos Anais de eventos
COBEM 2021
26th International Congress of Mechanical Engineering
On the Influence of the Wall Thickness Heterogeneity in the Mechanics of Intracranial Aneurysms
Submission Author:
Iago Lessa Oliveira , SP , Canada
Co-Authors:
Iago Lessa Oliveira, José Luiz Gasche, Julio Militzer, Carlos Baccin , Philip Cardiff
Presenter: Iago Lessa Oliveira
doi://10.26678/ABCM.COBEM2021.COB2021-0451
Abstract
Although intracranial aneurysms (IAs) have been extensively investigated in the last three decades by using numerical techniques, the bulk of these works have been focused on using Computational Fluid Dynamics (CFD) to simulate the blood flow, since substantial evidence shows that hemodynamics plays a crucial role in this pathology. However, most works assumed the vascular tissue as rigid, i.e., ignoring the effect of its elasticity. This is an understandable choice because the main subject of study was the hemodynamics and, if patient-specific blood flow information is already hard to obtain, data on an IA’s wall tissue properties are even scarcer. Nevertheless, it is well known that arteries exhibit nonlinear and anisotropic constitutive behavior with heterogeneous mechanical properties. Moreover, the vascular wall does not have uniform thickness. Relatively few works have investigated the impact of wall tissue modeling on the mechanics of IAs: some of them have focused on the hemodynamics without presenting the eventual changes on tissue stress and deformation; while others have numerically simulated the IA sac only — isolating the aneurysm and removing the vascular branches — by using a membrane model approach that assumed a uniform thickness throughout the aneurysm. To have better models to study the mechanics of IAs in a Fluid-Solid Interaction (FSI) context and while patient-specific data is not routinely collected yet, it is important to understand the impact of modeling choices on the wall mechanics of this pathology since an IA rupture, that physicians ultimately try to prevent, is a wall-exclusive event that depends on the level of stresses. In this context, this work investigates the influence of thickness heterogeneity directly on the wall mechanics for the St. Venant-Kirchhoff and the neo-Hookean models by numerically simulating a pressure-inflation model of two patient-specific vasculatures with ruptured and unruptured IAs, collected from medical images. We used the library solids4foam, an extension of the CFD library foam-extend, that implements the Finite Volume Method (FVM) to solve solid deformation problems. Our results suggest that the uniform thickness modeling choice throughout the vasculature may overestimate or underestimate the von Mises stress on the aneurysm depending on the value of this uniform thickness. Furthermore, this seems to be consistent for different constitutive laws. Therefore, it is essential to account for a realistic modeling of the wall thickness distribution on a vasculature when investigating IA wall mechanics.
Keywords
Intracranial aneurysms, aneurysm wall mechanics, heterogeneous thickness, solids4foam
