Stereoscopically Observed Deformations of a Compliant Abdominal Aortic Aneurysm Model

International audienceBackground: Computational models of abdominal aortic aneurysm (AAA) have aimed to address the limited understanding of aneurysm rupture and their development. Fluid solid interaction (FSI) modeling provides an approach that allows for calculation of stress within the wall and wall shear stress. The experimental validation of this approach has been limited by its lack of consideration of the large and varied deformations the AAA undergoes in response to physiologic flow and pressure. Method and Approach: Towards addressing the issue of accurately modeling this deformation experimentally, a stereoscopic imaging system was constructed to measure model aneurysm displacement in response to pressurization. The device demonstrated adequate accuracy (locations within 0.07 mm) for capturing local variation, while allowing the full length of the aneurysm sac to be observed at once. The model shapes, consisting of healthy aorta, AAA with bifurcation, and AAA without bifurcation, were also evaluated computationally using finite elements to assess the impact of differences between material properties and to compare against the experimental inflation test. Results: The experimental material demonstrated realistic AAA behavior, producing clinically observed levels of cyclic strain (1-2% circumferentially), where cyclic strain is the strain occurring between diastolic and systolic pressures. Conclusions: The technique also captured regional variations of strain that are unobservable with diameter measures alone. However, the experimental material has a time-dependent aspect not reported in tissue tests. The results of the computations show that an asymmetric aortic bifurcation created displacement differences but not cyclic strain differences within the aneurysm sac