Hemodynamics and bio-mechanics of morphologically distinct saccular intracranial aneurysms at bifurcations: Idealised vs Patient-specific geometries.

Understanding the factors that influence the rupture of aneurysms is of primary concern to the clinicians, who are grappled with patient management. It is important to know how the relation between morphological features of the cerebral aneurysm, and the mechanical stresses on the containing arterial walls are influenced by the hemodynamic forces. Present study investigates three different shapes, which have been identified correspondingly in patient-specific scenarios as well. The primary objective is to categorize the bifurcation aneurysms into standard shapes such as, spherical, beehive and pear-shaped, based on patient-specific clinical studies and further compare and contrast the model aneurysms with the patient specific configurations, for their hemodynamic factors as well as the attendant stresses on the wall. MethodsComputational fluid dynamic simulations are performed accounting for the fluid-structure interaction (FSI) effects between the flowing fluid and the containing vessel wall. Blood is assumed to be Newtonian, while the arterial walls are assumed to be linearly elastic. A commercial solver is used for performing detailed calculations. Hemodynamic and bio-mechanical rupture predictions are carried out for the three different shapes. Observations derived from the idealised simulations are compared and contrasted against their patient-specific counterparts. ResultsFrom detailed numerical simulations, it was observed that pear-shaped aneurysms exhibit large re-circulation bubble and flow stagnation zone, with higher residence time for the particles, which may lead to atherosclerotic lesions. Beehive shape allows for maximum flow into the aneurysmal sac with concentrated jet impinging on the dome, leading to high values of maximum WSS (MWSS) resulting in great propensity to form a secondary bleb. However, flow field inside a spherical aneurysm is found to be stable with fewer vortices, and nearly uniform distribution of wall stresses are observed though-out the sac, which perhaps signifies hemodynamically and bio-mechanically stable condition. ConclusionCategorizing patient-specific intracranial aneurysms into standard shapes viz, spherical, beehive and pear could generalize the process of prediction of hemodynamic and bio-mechanical rupture indicators. Comparative assessment of the flow field and stresses reported from the simulations on idealised models, with corresponding patient-specific simulations reveal that, these studies could aid in understanding the generalised shape dependence of hemodynamic and bio-mechanical behaviour of aneurysms.