Analysis of type I endoleaks in a stented abdominal aortic aneurysm.

To improve the performance of endovascular grafts used for the treatment of abdominal aortic aneurysms, we develop a methodology to analyze the phenomena of type I endoleaks in a non-invasive-stented abdominal aorta. As one aspect of this study, an evaluation of the parietal stresses generated by the blood flow is provided. As blood is known to be a shear-thinning, non-Newtonian fluid, we have chosen to use the Phan-Thien and Tanner model, which can be derived from the rheology of polymer solutions. As a second aspect, we develop an axisymmetric finite-element model of the complete system. An explicit finite-element in-house code, is used to simulate the behavior of the system, which is subjected to hydrostatic pressure and to the stresses generated by the blood flow. As the response of the solid is strongly affected by the response of the fluid, and vice versa, the modeling of a coupled fluid-structure interaction is achieved in this work. This study provides an evaluation of the stresses generated by the blood flow on the aorta's wall. The finite-element model allows to identify biomechanical factors that can influence the propensity of an aneurysm treated with an endograft, to exhibit endoleaks. First observations are made concerning the influence of oversizing of the endograft and the influence of friction coefficients between the aorta, endograft and plaque.