Quantitative Effects of Coil Packing Density on Cerebral Aneurysm Fluid Dynamics: An In Vitro Steady Flow Study

Abstract

Over the past 15 years, coil embolization has emerged as an effective treatment option for cerebral aneurysms that is far less invasive than the long-standing convention of surgical clipping. However, aneurysm recurrence after coil embolization is not uncommon: recurrence rates as high as 50% have been reported in the literature. One factor that may contribute to recurrence after coiling is residual flow into the aneurysmal sac. At present, there is limited quantitative knowledge of the relationship between coil packing density and aneurysmal inflow. We present an in vitro fluid dynamic study of basilar tip aneurysm models that elucidates this relationship. At physiologically normal flow rates, we found that a packing density of 28.4% decreased aneurysmal inflow by 31.6% in a wide-neck model, and that a packing density of 36.5% decreased aneurysmal inflow by 49.6% in a narrow-neck model. Results also indicated that coiling reduced aneurysmal inflow more significantly at lower parent vessel flow rates, and that coiling reduced neck-plane velocity magnitudes more significantly for narrow-neck aneurysms. Our study provides novel quantitative information that could ultimately contribute to improved outcomes for patients with cerebral aneurysms by enabling more effective coil embolization.

Influence of stent configuration on cerebral aneurysm fluid dynamics

“…Our study also reports significant changes, one example of which is that stents, in some cases, reduced aneurysmal inflow by margins comparable to those reported for embolic coils (Babiker et al, 2010). In addition, our study demonstrates that stent configuration has a significant influence on aneurysmal fluid dynamics.…”

“…A lost-core Sylgard s model of an idealized wide-neck basilar tip aneurysm was constructed using a process previously reported by our group (Babiker et al, 2010). The model, shown later in Fig.…”

Effects of anatomic characteristics of aneurysms on packing density in endovascular coil embolization: analysis of a single center’s experience

“…Therefore, the conventionally recommended VER of 20-25 % can be roughly interpreted as 15.5-19.4 % when the volume is digitally measured using 3D-RA, and a VER of 20 % was set as the minimum requirement in our practice. It may be controversial to set a single VER value as a goal, because in vitro experiments and computational fluid dynamic studies have shown that a hemodynamically effective VER is dependent on neck size, lateral wall type or terminal type, and the angle made by a sac and its parent artery [1,20]. Therefore, 20 % of VER is always a minimum requirement and we aim to embolize as densely as possible.…”

How Do Coil Configuration and Packing Density Influence Intra-Aneurysmal Hemodynamics?

“…This finding is consistent with previous CFD-based studies and in vitro experiments. 13,15,19,20,26 Particular flow patterns were visualized due to the coil configuration (Fig 2B), which are associated with the special location of the coils at the aneurysm ostium. Specific flow characteristics also were reported by an in vivo study, in which short and disturbed streamlines were found near the aneurysm wall.…”