Abstract Number ‐ 58: Effects of Neck Geometry on Reccurence in CFD Analysis for Aneurysms after Low VER Coiling

Abstract

Introduction Although low volume embolization ratio is known as risk factor of aneurysmal recanalization, stable occlusion can be achieved in limited cases. Evaluation of hemodynamic parameters at the neck surface has usually been performed with a flat surface rather than a curved surface following the actual coil shape. In this study, we investigated the effect of the geometry of the neck surface on hemodynamics related to aneurysm recanalization after coil embolization in low volume embolization ratio. Methods We focused on aneurysms of 5–10 mm in size that were conducted coil embolization with 15–20% volume embolization ratio (low‐VER). Aneurysms that were recanalized after coil embolization and conducted additional coil deployment were defined as the recanalized case. We identified 25 aneurysms (7 recanalized and 18 stable). We randomly selected 3 recanalized cases and 6 stable cases. For each case, the three‐dimensional vascular geometry including aneurysm was reconstructed by preoperative angiographic images. To divide the aneurysm from the parent artery, two types of neck surfaces (flat neck surface and curved neck surface) were generated for each case. The embolized coil was modeled in the enclosed area with the neck plane and aneurysmal wall by our original virtual coiling simulation. CFD analyses were conducted with the flat neck surface and the curved neck surface. We estimated 6 morphological parameters and 35 hemodynamic parameters, and the mean values of hemodynamic parameters were compared between the flat neck surface and the curved neck surface. The change rate of each parameter in the curved neck was calculated based on that in the flat neck. Results Since the velocity and pressure were involved in recanalization factors by the previous studies, as illustrative hemodynamic parameters, the mean values and change rate of the spatially averaged velocity normal to the neck surface into the cerebral aneurysm (NVneck) and the pressure difference between the average pressure on the surface of control volume and the maximum pressure at the neck surface (PDneck) were summarized in Table 1. These parameters were higher with the curved neck surface geometry case than with the flat neck surface geometry case. Furthermore, the change rates were higher in the recanalized cases compared to those in the stable cases. Conclusions In the CFD analysis with the curved surface, the averaged inflow velocity and pressure difference at the neck surface were higher than those with the flat surface. In addition, the change rates of hemodynamic parameters in recanalized cases were higher than those of stable cases. Therefore, the hemodynamic parameters are changed depending on the geometry of the neck surface, which may affect the prediction accuracy for recanalization using CFD.