We have applied methodologies to investigate the role played by the native abdominal aortic aneurysm geometry on the flow-induced wall stress in the presence of an intact aneurysm and after its surgical repair. This research led to the development of a procedure for the calculation of shear stresses at the inner wall of dilated large arteries and is currently conducted within the context of improving the assessment of aneurysm rupture potential and design of endovascular grafts used for repair. The modeling approach taken in this research differentiates us from other researchers in the field in that we have hypothesized that the stresses at the blood vessel wall are primarily caused by the dynamics of pulsatile blood flow rather than wall mechanics alone induced by a uniform intraluminal pressure. As such, our fluid-structure interaction modeling of (cerebral and aortic) aneurysm geometries has led to more accurate predictions of the flow-induced stresses on the vessel wall that are deemed to increase the risk of rupture of these aneurysms. To this end, we are currently developing numerical techniques to (i) determine the zero-pressure geometry of blood vessels under in vivo flow conditions directly from medical images; (ii) calculate outflow conditions from patient-specific blood flow velocity derived from magnetic resonance imaging (MRI); (iii) generate a constitutive anisotropic model for the characterization of aneurysm tissue material properties; (iv) calculate geometry-based indices derived from computed tomography (CT) images of ruptured and non-ruptured aneurysms to evaluate the significance of geometry in rupture potential and its correlation with wall mechanics; (v) validate the computational predictions with in vitro experimental techniques (PIV) and dynamic imaging techniques (phase contrast- and cine-MRI); (vi) estimate non-invasively the thickness distribution of the aortic wall by means of image processing algorithms, giving us an unprecedented contribution to the accurate assessment of the biomechanical environment of diseased arteries.
Schematic of research activities associated with abdominal aortic aneurysm biomechanics.