A New Method for Simulating Embolic Coils as Heterogeneous Porous Media

Purpose: To gain insight into the influence of coils on aneurysmal hemodynamics, computational fluid dynamics (CFD) can be used. Conventional methods of modeling coils consider the explicit geometry of the deployed devices within the aneurysm and discretize the fluid domain. However, the complex geometry of a coil mass leads to cumbersome domain discretization along with a significant number of mesh elements. These problems have motivated a homogeneous porous medium coil model, whereby the explicit geometry of the coils is greatly simplified, and relevant homogeneous porous medium parameters are approximated. Unfortunately, since the coils are not distributed uniformly in the aneurysm, the homogeneity assumption is no longer valid. Methods: In this paper, a novel heterogeneous porous medium approach is introduced. To verify the model, we performed CFD simulations to calculate the pressure drop caused by actual deployed coils in a straight cylinder. Next, we considered three different anatomical aneurysm geometries virtually treated with coils and studied the hemodynamics using the presented heterogeneous porous medium model. Results: We show that the blood kinetic energy predicted by the heterogeneous model is in strong agreement with the conventional approach. The homogeneity assumption, on the other hand, significantly over-predicts the blood kinetic energy within the aneurysmal sac. Conclusions: These results indicate that the benefits of the porous medium assumption can be retained if a heterogeneous approach is applied. Implementation of the presented method led to a substantial reduction in the total number of mesh elements compared to the conventional method, and greater accuracy was enabled by considering heterogeneity compared to the homogenous approach.