How do coil configuration and packing density influence intra-aneurysmal hemodynamics?

Abstract

Background and purpose: Endovascular coiling is a well-established therapy for treating intracranial aneurysms. Nonetheless, postoperative hemodynamic changes induced by this therapy remain not fully understood. The purpose of this work is to assess the influence of coil configuration and packing density on intra-aneurysmal hemodynamics.

Materials and methods: Three 3D rotational angiography images of 3 intracranial aneurysms before and after endovascular coiling were used. For each aneurysm, a 3D representation of the vasculature was obtained after the segmentation of the images. Afterward, a virtual coiling technique was used to treat the aneurysm geometries with coil models. The aneurysms were coiled with 5 packing densities, and each was generated by using 3 coil configurations. Computational fluid dynamics analyses were carried out in both untreated and treated aneurysm geometries. Statistical tests were performed to evaluate the relative effect of coil configuration on local hemodynamics.

Results: The intra-aneurysmal blood flow velocity and wall shear stress were diminished as packing density increased. Aneurysmal flow velocity was reduced >50% due to the first inserted coils (packing density <12%) but with a high dependency on coil configuration. Nonsignificant differences (P > .01) were found in the hemodynamics due to coil configuration for high packing densities (near 30%). A damping effect was observed on the intra-aneurysmal blood flow waveform after coiling.

Conclusions: Intra-aneurysmal hemodynamics are altered by coils. Coil configuration might reduce its influence on intra-aneurysmal hemodynamics as the packing density increases until an insignificant influence could be achieved for high packing densities.

Fig 1.

Results of virtual coiling for case 2. Untreated model (A) and treated models corresponding to coil packing densities of 5.6% (B), 11.2% (C), 16.7% (D), 22.2% (E), and 30.0% (F).

Fig 2.

Blood flow velocity magnitudes in gray-scale for an aneurysm cross-section at peak systole for case 2. A, Changes in the velocity are presented with a fixed coil configuration and increasing packing density. B, Two coil configurations are compared for packing densities of 11.2% and 16.7%. The coils are presented in yellow and the percentages represent the packing densities achieved for each model.

Fig 3.

WSS distributions for the untreated and several treated models for case 2, calculated at peak systole (A) and end diastole (B).

Fig 4.

A, Time-averaged intra-aneurysmal mean flow velocity reduction rate. B, Time-averaged WSS in the aneurysm dome.

Fig 5.

Variation of the aneurysm areas with low and high WSS expressed as a percentage of the whole aneurysm dome during one cardiac cycle for case 2. A, Untreated model. B and C, treated models with packing densities of 22.2% and 30.0%, respectively.