Flow changes caused by the sequential placement of stents across the neck of sidewall cerebral aneurysms

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Abstract
The goal of this study was to quantify the reduction in velocity, vorticity, and shear stresses resulting from the sequential placement of stents across the neck of sidewall cerebral aneurysms. A digital particle image velocimetry (DPIV) system was used to measure the pulsatile velocity field within a flexible silicone sidewall intracranial aneurysm model and at the aneurysm neck-parent artery interface in this model. The DPIV system is capable of providing an instantaneous, quantitative two-dimensional measurement of the velocity vector field of "blood" flow inside the aneurysm pouch and the parent vessel, and its changes at varying stages of the cardiac cycle. The corresponding vorticity and shear stress fields are then computed from the velocity field data. Three Neuroform stents (Boston Scientific/Target), each with a strut thickness between 60 and 65 microm, were subsequently placed across the neck of the aneurysm model and measurements were obtained after each stent had been placed. The authors measured a consistent decrease in the values of the maximal averaged velocity, vorticity, and shear stress after placing one, two, and three stents. Measurements of the circulation inside the sac demonstrated a systematic reduction in the strength of the vortex due to the stent placement. The decrease in the magnitude of the aforementioned quantities after the first stent was placed was remarkable. Placement of two or three stents led to a less significant reduction than placement of the first stent. The use of multiple flexible intravascular stents effectively reduces the strength of the vortex forming in an aneurysm sac and results in a decrease in the magnitude of stresses acting on the aneurysm wall.
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