Hemodynamic differences in intracranial anerusysm blebs due to blood rheology

Computational blood flow simulations over patient-specific image-based three dimensional domains under personalized flow conditions have been extensively used to investigate associations between flow characteristics and aneurysm initiation, progress and rupture. Although it is widely accepted that the wall shear stress is associated to those processes, there is still no agreement about what stress characteristics are responsible for triggering those biomechanical processes. Although the incorporation of the blood rheology in large arterial systems containing aneurysms resulted in similar hemodynamic characterizations for most aneurysms, large aneurysms, especially those containing blebs, are expected to have flow rates in the range where Newtonian and non-Newtonian models largely differ. However, there is no consent among authors about the impact of blood rheology on the intraaneurysmal wall shear stress magnitude. In this work we used high resolution models reconstructed from rotational angiography images to perform unsteady finite element blood flow simulations to investigate the differences in WSS distribution and alignment for Newtonian and non-Newtonian rheologies. Unstructured finite element meshes were generated using an advancing front technique. Personalized flow conditions were imposed at the inlets of the models. The Casson model was incorporated as a velocity-dependent apparent viscosity and the results were compared to those using the Newtonian rheology. Associations between the localization of regions with large differences in wall shear stress magnitude and orientation, and the regions of differentiated wall shear stress magnitude were studied in a cohort of patients.