Anatomically shaped internal carotid artery aneurysm in vitro model for flow analysis to evaluate stent effect

Abstract

Background and purpose: Stent implantation alone might not be sufficient to produce definitive treatment of cerebral aneurysms. Therefore, extended experimental work is needed to improve results. We show the feasibility of using an in vitro anatomically shaped elastic model for flow evaluation before and after stent implantation.

Methods: Based on human vascular casting, an anatomic elastic internal carotid artery model, including an aneurysm on the supraclinoid portion, was manufactured. The model was connected to a circulatory loop to simulate physiological flow. After visualization of the flow by using glass particles and laser sheet translumination, the digitally recorded data were transferred for computer analysis. Intra-saccular flow pattern changes and the vortex velocity reduction induced by the stent were investigated qualitatively and quantitatively.

Results: The distal neck of the aneurysm behaved as a flow divider. Therefore, it was directly exposed to the hemodynamic stress. Inside the sac, a well-defined vortex formed and progressed along the wall toward the proximal neck. After stent implantation this pattern changed significantly; the vortex appeared more dispersed and its residence time increased. The velocity reduction was 32%. Velocity peak was observed close to the distal neck in both cases.

Conclusion: In vitro anatomic elastic models are feasible for flow evaluation with laser sheet translumination. In our model, stent implantation resulted in hemodynamic changes that might favor the exclusion of the aneurysm from the circulation and can prevent regrowth of the aneurysmal sac.

Fig 1.

Elastic anatomic model with physiological curves of internal carotid artery and with aneurysm located on supraclinoid segment. Arrows show increased flow intensity at these points, caused by centrifugal effect of fluid.

Fig 2.

Lateral cross-section view of aneurysm model with implanted stent across neck.

Fig 3.

Experimental setup.

Fig 4.

Gallery of images of non-stented aneurysm obtained every 0.04 s. A, Native images. B, Subsequent subtraction images.

Fig 5.

Gallery of images of stented aneurysm obtained every 0.04 s. A, Native images. B, Subsequent subtraction images.

Fig 6.

Trajectories of subsequent subtracted vortex advancement (SVC path line). Arrow shows flow unsteadiness due to effect of next vortex entering into cavity. A, Non-stented model. B, Stented model.

Fig 7.

Graphs show SVC velocity and position values. A, Direct velocity. Velocity of vortices in function of time shows pulsatile characteristics of flow. B, Indirect velocity. Trajectory length of vortex advancement (SVC position values) in function of time represents velocity of vortices. C, Trajectory length in function of power of time.

Fig 8.

Images of models obtained every 0.12 s. A, Non-stented model. B, Stented model.