Hemodynamic changes due to stent placement in bifurcating intracranial aneurysms.

OBJECT The aim of this study was to measure changes in intraaneurysm flow dynamics and mechanical stresses resulting from the placement of Neuroform stents in bifurcating intracranial aneurysm models. METHODS A digital particle image velocimetry (DPIV) system was used to measure the pulsatile velocity and shear stress fields within the aneurysm and at the aneurysm neck-parent artery interface. The DPIV system provides an instantaneous two-dimensional measurement of the temporal and spatial variations of the velocity vector field of the flow inside the aneurysm pouch and the parent vessel, providing information on both the temporal and spatial variations of the velocity field during the entire cardiac cycle. The corresponding shear stress field was then computed from the velocity field data. A flexible silicone model of bifurcating intracranial aneurysms was used. Two Neuroform stents with a 60- to 65-microm strut thickness and an 11% metal/artery ratio were placed in a Y-configuration, and measurements were obtained after placing the stents. CONCLUSIONS Two three-dimensional vortices of different strengths persisted within the aneurysm during the entire cardiac cycle. The peak velocity and strength of these vortices were reduced after placing the two bifurcating stents. The effect of placing the Neuroform stent across the neck of a bifurcating intracranial aneurysm was shown to reduce the magnitude of the velocity of the jet entering the sac by as much as 11%. Nevertheless, the effect of the stents was particularly noticeable at the end of the cardiac cycle, when the residual vorticity and shear stresses inside the sac were decreased by more than 40%.