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

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Object. 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.

Methods. 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 µm, 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.

Conclusions. 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.

Article Information

Address reprint requests to: Gádor Cantón, Ph.D., Department of Mechanical and Aerospace Engineering, University of California, San Diego, 9500 Gilman Drive, MC 0411, La Jolla, California 92093–0411. email: gcanton@mae.ucsd.edu.

© AANS, except where prohibited by US copyright law.

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Figures

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    Photograph showing the sidewall aneurysm model and geometrical data relevant to the study.

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    Graph showing the waveform corresponding to flow in the carotid artery, which was supplied to the sidewall aneurysm model.

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    Images obtained using the DPIV system showing the velocity field in the parent artery as well as within the aneurysm sac throughout the cardiac cycle. Panels correspond to the stages (a–l) indicated in Fig. 2.

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    Schematic drawing showing the effect of the flow pattern in the aneurysm sac downstream from the parent vessel.

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    Images generated by the DPIV system showing the velocity magnitude field (m/second) inside the aneurysm sac throughout the cardiac cycle. Panels correspond to the stages indicated in Fig. 2.

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    Images generated by the DPIV system showing the vorticity field (1/second) inside the aneurysm sac throughout the cardiac cycle. Panels correspond to the stages indicated in Fig. 2.

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    Images generated by the DPIV system showing the stress field (1/second) inside the aneurysm sac of the control model. Panels correspond to the stages indicated in Fig. 2.

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    Graphs showing a comparison of the velocity fields at the peak systole corresponding to the control model (upper left) and the experimental models after placement of one (upper right), two (lower left), and three (lower right) stents.

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    Graphs showing a comparison of the shear stress fields at peak systole corresponding to the control model (upper left) and the experimental models after placement of one (upper right), two (lower left), and three (lower right) stents.

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    Graphs demonstrating a comparison of the vorticity fields at peak systole corresponding to the control model (upper left) and the experimental models after placement of one (upper right), two (lower left), and three (lower right) stents.

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    Graphs demonstrating a comparison of the change with time of the absolute value of the circulation for the control model and the experimental models. Upper: Changes in circulation due to the placement of one stent. Center: Changes due to two stents. Lower: Changes due to three stents.

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