PurposeThe purpose of this study is to explore the influence of segmentation of the upstream and downstream parent artery and hemodynamic boundary conditions (BCs) on the evaluated hemodynamic factors for the computational fluid dynamics (CFD) analysis of intracranial aneurysms.Materials and MethodsThree dimensional patient-specific aneurysm models were analyzed by applying various combinations of inlet and outlet BCs. Hemodynamic factors such as velocity pattern, streamline, wall shear stress, and oscillatory shear index at the systolic time were visualized and compared among the different cases.ResultsHemodynamic factors were significantly affected by the inlet BCs while there was little influence of the outlet BCs. When the inlet length was relatively short, different inlet BCs showed different hemodynamic factors and the calculated hemodynamic factors were also dependent on the inlet length. However, when the inlet length (L) was long enough (L>20D, where D is the diameter of inlet section), the hemodynamic factors became similar regardless of the inlet BCs and lengths. The error due to different inlet BCs was negligible. The effect of the outlet length on the hemodynamic factors was similar to that of the inlet length.ConclusionSimulated hemodynamic factors are highly sensitive to inlet BCs and upstream parent artery segmentation. The results of this work can provide an insight into how to build models and to apply BCs for more accurate estimation of hemodynamic factors from CFD simulations of intracranial aneurysms.

Multiple aneurysms occur rarely and have not been well investigated. The purpose of this study is to verify whether high rupture risk of multiple aneurysms is due to the interaction between multiple aneurysms' geometrical characteristics. The following geometrical characteristics were varied in an idealized sidewall-type model: aneurysm a 1 's dome-neck length (S), size ratio, inflow angle (a), distance between two aneurysms (D), and the parent vessel's angle (u). We varied the parent blood vessel and aneurysm sac a 1 's geometrical characteristics to analyze their hemodynamic influence on aneurysm a 2 . By comparing the influence on aneurysm a 2 , we found that parent blood vessel geometrical characteristics such as the distance between aneurysms (D) and the parent vessel's angle (u) were the most hemodynamically influential characteristics examined. The impact of varying the aneurysm's geometrical characteristics such as dome-neck length (S), size ratio, and inflow angle (a) was not obvious. The reason for the higher rupture rate of multiple aneurysms is not due to interactions between the aneurysm sacs but due to factors of each individual aneurysm.