The effect of intracranial stent implantation on the curvature of the cerebrovasculature

Abstract

Background and purpose: Recently, the use of stents to assist in the coiling and repair of wide-neck aneurysms has been shown to be highly effective; however, the effect of these stents on the RC of the parent vessel has not been quantified. The purpose of this study was to quantify the effect of intracranial stenting on the RC of the implanted artery using 3D datasets.

Materials and methods: Twenty-four patients receiving FDA-approved neurovascular stents to support coil embolization of brain aneurysms were chosen for this study. The stents were located in the ICA, ACA, or MCA. We analyzed C-arm rotational angiography and contrast-enhanced cone beam CT datasets before and after stent implantation, respectively, to ascertain changes in vessel curvature. The images were reconstructed, and the vessel centerline was extracted. From the centerline, the RC was calculated.

Results: The average implanted stent length was 25.4 ± 5.8 mm, with a pre-implantation RC of 7.1 ± 2.1 mm and a postimplantation RC of 10.7 ± 3.5 mm. This resulted in a 3.6 ± 2.7 mm change in the RC due to implantation (P < .0001), more than a 50% increase from the pre-implantation value. There was no difference in the change of RC for the different locations studied. The change in RC was not impacted by the extent of coil packing within the aneurysm.

Conclusions: The implantation of neurovascular stents can be shown to have a large impact on the RC of the vessel. This will lead to a change in the local hemodynamics and flow pattern within the aneurysm.

Fig 1.

Illustrative case of a 61-year-old female with family history of aneurysmal subarachnoid hemorrhage. MR angiography revealed a left ICA terminus aneurysm. Catheter angiography demonstrated a 2.5 mm aneurysm having a 2 mm neck (A, frontal oblique projection) that subsequently underwent stent assisted coil embolization (B, frontal oblique projection). Pre-embolization 3DRA (C) and post-embolization CBCT (D) are used to isolate a 3D model of the stented artery (pre-embolization, E; post-embolization, F). The centerlines of the stented vascular segment pre and post stent-assisted coiling are extracted in G and H, respectively.

Fig 2.

The best-fit polynomial (green line) of the resampled centerline data (blue triangles) is used to calculate the radii of curvature before (top) and after (bottom) stent implantation.

Fig 3.

Rotational angiography (A) and contrast-enhanced CBCT (B) of 1 of the vascular phantoms. Bland-Altman plot (C) of the differences in the radii of curvature measured based on data obtained from each imaging technique (bold dashed line is the mean difference; dotted lines are the limits of the agreement).

Fig 4.

A, Box-and-whisker plots showing the radii of curvature before and after stent implantation (***, P < .0001, paired t test). B, Histogram of the increase of the radii of curvature from pre- to post-stent implantation.

Fig 5.

Box-and-whisker plot of the change in the radius of curvature due to stent implantation based on the anatomic location of the aneurysm.

Fig 6.

Linear regression analysis of the effect of packing attenuation on changes in the radius of the curvature of the stented segment (P > 0.05; R² = 0.002).