Computational methods applied to analyze the hemodynamic effects of flow-diverter devices in the treatment of cerebral aneurysms: Current status and future directions

Flow diverter (FD) devices have been widely employed to treat cerebral aneurysms. Despite the well-documented clinical benefits, considerable inter-patient variability in clinical outcome has been reported, which implies the necessity of patient-specifically evaluating hemodynamic changes following FD treatment, especially those associated with posttreatment intra-aneurysmal thrombus formation or complications. Computational fluid dynamics (CFD) methods, owing to the advantages in hemodynamic quantification, cost, and flexibility over traditional in vivo measurement or in vitro experiment methods, have increasingly become a major means for addressing hemodynamic problems related to FD treatment. Relevant CFD-based studies have extensively demonstrated that the results of hemodynamic computation can reasonably explain the clinical outcomes in different patient cohorts and provide useful insights for guiding the selection or optimization of FD devices. Nevertheless, CFD models are inherently unable to predict FD implantation-induced mechanical changes in the walls of aneurysm and its parent artery. In addition, the boundary conditions of most existing CFD models were not fully personalized for purpose of simplicity or due to the difficulty of measuring flow velocity in near-aneurysm regions, which may however considerably compromise the fidelity of the models in reproducing in vivo hemodynamics. To address these issues, the following studies would be expected: (1) perform fluid structure interaction simulations to explore the associations between wall stress/tension and posttreatment adverse vascular remodeling or aneurysm rupture, and (2) develop geometrical multiscale models based on available in vivo data to generate patient-specific boundary conditions for CFD models localized to aneurysm regions.