Fluid-solid interaction simulation of flow and stress pattern in thoracoabdominal aneurysms: A patient specific study

Thoracoabdominal aneurysm (TA) is a pathology that involves the enlargement of the aortic diameter in the inferior descending thoracic aorta and has risk factors including aortic dissection, aortitis or connective tissue disorders (Webb, T. H. and Williams, G. M. 1999). Abnormal flow patterns and stress on the diseased aortic wall are thought to play an important role in the development of this pathology and the internal wall stress has proved to be more reliable as a predictor of rupture than the maximum diameter for abdominal aortic aneurysms (Fillinger, M. F., et al. 2003). In the present study, two patients with TAs of different maximum diameters were scanned using magnetic resonance imaging (MRI) techniques. Realistic models of the aneurysms were reconstructed from the in vivo MRI data acquired from the patients, and subject-specific flow conditions were applied as boundary conditions. The wall and thrombus were modeled as hyperelastic materials and their properties were derived from the literature. Fully coupled fluid-solid interaction simulations were performed for both cases using ADINA 8.2. Results were obtained for both the flow and wall stress patterns within the aneurysms. The results show that the wall stress distribution and its magnitude are strongly dependent on the 3-D shape of the aneurysm and the distribution of thrombus.