Realistic comparison between aneurysmal wall shear stress vector and blood rheology in patient-specific computational hemodynamic models

摘要

Wall shear stress plays an important role in the development of cerebrovascular pathologies. Its impact on aneurysm initiation, progress and rupture, was reported in previous works during the last years. However, there is still no wide agreement about what WSS characteristics are responsible for triggering those biomechanical processes. The accuracy of the simulations has been successfully validated in the past. 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 WSS 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. Flow rate wave form was imposed at the inlets after scaling according to the Murray's Law for optimal arterial networks. 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.