Prestressing and other model complexities in simulation of patient-specific abdominal aortic aneurysms

Rupture of abdominal aortic aneurysm (AAA) is the 13th leading cause of death in western society and is fatal in 70-90%. In consequence, precise prediction of AAA rupture risk is essential. In recent years, many groups around the world have started to address the issue of predicting the individual patient-specific rupture risk by means of different interdisciplinary approaches including histological, medical imaging, experimental and mechanical simulation. In this contribution we focus on the important aspect of obtaining realistic stress distributions and deformations of the AAA wall by means of simulation using the finite element method. One important aspect in the before mentioned models in patient-specific simulation is to accurately consider loading that has occurred at the time of in vivo imaging. Because of this loading the geometry obtained from such imaging can obviously not be considered stress-free. To get a realistic prestressing state is not a trivial task when dealing with large strains and complex geometries. Hence, in literature geometries very often are assumed to be stress-free neglecting the loads present at the time of imaging. In this talk we will propose two methods that can be used to determine the prestressing state of patient-specific AAAs in a finite deformation context and will give some remarks on their pros and cons. In addition we will demonstrate in a series of cases, i.e. patients, how dramatically results are influenced by different modeling assumptions. Assumptions that are included are different constitutive models and consideration of aspects like intraluminal thrombus (ILT), prestressing and calcifications.