Flow Visualization Study of Bifurcation Aneurysm: Intraaneurysmal Flow and Aspect Ratio (dome/neck)

Abstract

Summary: We carried out flow visualization studies and measurement of intraaneurysmal flow velocity using a set of three-dimensional bifurcation aneurysm models of various aspect ratio (AR＝ dome/neck). The aneurysm models were made by an acryl according to computer specification. Flow visualization was performed using the dye injection method. Stream lines in the aneurysm models were monitored and evaluated under various flow ratios into the branches. A mean transit time was calculated by height-over-area method from the time-related concentration of the injected dye in the aneurysm that can be fitted to the exponential curve. Fundamental aneurysm flow was composed of inflow, circulation flow and outflow. A certain asymmetry of the flow ratio was necessary for a significant intraaneurysmal circulation to develop. Mean transit times correlated well with aspect ratio: 5.90 at AR1.0, 17.74 at AR 1.5, 38.36 at AR 2.0 and 75.96 at AR 3.5. Mean transit times became dramatically slow when AR changed from 1.5 to 2.0 and almost stagnant flow was noticed at dome side of aneurysm with AR 3.5.