Numerical Analysis of Bifurcation Angles and Branch Patterns in Intracranial Aneurysm Formation

BACKGROUND Hemodynamic factors, especially wall shear stress (WSS), are generally thought to play an important role in intracranial aneurysm (IA) formation. IAs frequently occur at bifurcation apices, where the vessels are exposed to the impact of WSS. OBJECTIVE To elucidate the relationship between bifurcation geometry and WSS for IA formation. METHODS Twenty-one bifurcation models varying in branch angles and branch diameters were made with 3-dimensional computer-aided design software. In all models, the value of maximum WSS (WSSMAX), the area of high WSS (AREA), and the magnitude of wall shear force over AREA () were investigated by the steady-flow simulation of computational fluid dynamics. RESULTS On the basis of statistical analysis, WSSMAX tended to be high when the bifurcation angle and/or branch diameter was small. AREA and significantly increase as the bifurcation and/or the branch angle became larger. CONCLUSION The magnitude of WSS strongly correlated with bifurcation geometry. In addition to high WSS, AREA and were thought to affect IA formation. Observed bifurcation geometry may predict IA formation. Large branch angles and small branch may increase the risk of IA formation.