Physician Northwestern Memorial Hospital, United States
Purpose: Packing density is a key determinant of intra-aneurysmal stasis following endovascular coiling, which in turn influences thrombus formation and long-term durability of treatment. Prior work has identified general thresholds for packing density but has not stratified outcomes by aneurysm size, coil size, or neck-to-diameter ratio. Understanding these relationships under realistic physiologic conditions has direct relevance for interventional neuroradiology.
Materials and Methods: Computational fluid dynamics (CFD) simulations were performed using patient-derived intracranial vasculature reconstructed from magnetic resonance angiography. Blood flow was modeled under physiologic pulsatile pressure and viscosity parameters. Virtual aneurysms of varying size and neck morphology were introduced, and aneurysms were “virtually” coiled at different packing densities with coils of varying diameters. Post-procedural intra-aneurysmal stasis was quantified, with >50% reduction in flow defined as a clinically meaningful threshold.
Results: Across all aneurysm models, a mean packing density of 16% was required to achieve >50% stasis. Smaller aneurysms ( < 6 mm) required higher packing densities, up to 22%, whereas larger aneurysms ( >10 mm) required as little as 12% (p < 0.0001). Coil diameter had no measurable effect on intra-aneurysmal stasis (p = 0.6383). Neck-to-diameter ratio strongly influenced outcomes: aneurysms with smaller neck-to-diameter ratios required approximately 14% packing density, while those with larger ratios required up to 30% (p = 0.0015).
Conclusion: CFD studies using physiologic parameters demonstrate that optimal packing density thresholds for achieving hemodynamic stasis vary significantly by aneurysm size and morphology, but not by coil diameter. Tailoring packing targets to aneurysm geometry under physiologic flow conditions may improve treatment durability and reduce recurrence.
