Image-based Computational Fluid Dynamics and Structural Analysis in Abdominal Aortic Aneurysms

Abdominal aortic aneurysm (AAA) is a localized dilatation of the aortic wall. The lack of an accurate AAA rupture risk index remains an important problem in the clinical management of the disease. To accurately estimate AAA rupture risk, detailed information on patient specific wall stress distribution and aortic wall tissue yield stress is required. A complete fluid structure interaction (FSI) study of the wall forces is impractical and thus of limited clinical value. On the other hand, isolated static structural stress analysis based on a uniform wall loading is a widely used approach for AAA rupture risk estimation that however neglects flow induced wall stress variation. Aim of this study was to assess the merit of a decoupled fluid structure analysis of AAA wall stress. Anatomically correct patient specific AAA wall models were created by 3D reconstruction of computed tomography (CT) images. Flow simulations were carried out with inflow and outflow boundary conditions obtained from patient extracted data. Static structural stress analysis was performed applying a uniform pressure wall loading and a flow induced non-uniform pressure loading. In the structural analysis a hyperelastic arterial wall model and an elastic intraluminal thrombus (ILT) model were applied. Our results show that the decoupled fluid structural analysis approach yields a more realistic AAA wall stress distribution than the isolated structural stress analysis approach thus providing a practical alternative to the more complete but computationally intensive FSI study.