Hemodynamic-Structural Multi-Fidelity Assessment of Endovascular Flow Diversion Strategies for Cerebral Aneurysm Treatment: An Integrated Computational and Experimental Framework

Subarachnoid hemorrhage caused by a ruptured cerebral aneurysm carries a 50% fatality rate within the first month. Endovascular flow diversion is currently the standard treatment for such cases. However, there has never been a comprehensive study that simultaneously assesses the hemodynamic performance and structural behavior of different flow diversion strategies in a single framework.

Researchers constructed an aneurysm model using computed tomography imaging from a patient's CT scan. They then employed computational fluid dynamics to analyze various hemodynamic metrics for three flow diversion approaches: stents, coils, and the Woven Endo-Bridge. The team also utilized finite element analysis to evaluate the mechanical properties of stent geometries with different porosities made of 316L stainless steel, poly-L-lactic acid, and nitinol.

To validate their models, they conducted universal testing machine tests on printed polylactic acid and thermoplastic polyurethane analogues, and performed dimensional and elastic-tube analyses to ensure scale equivalence between their finite element analysis and universal testing machine geometries, as well as the rigid-wall computational fluid dynamics assumption.

Patient-specific computational fluid dynamics simulations revealed a high-risk hemodynamic profile. The stent option resulted in the lowest peak intra-saccular velocity, the greatest pressure reduction, near-zero wall shear stress, the only reduction in time-averaged wall shear stress, the largest cycle-averaged TAWSS, and the most significant peak-systolic velocity, wall shear stress, and vorticity reductions among all three strategies.

Both oscillatory shear index and rapid reaction ratio increased for all three treated configurations, aligning with the expected hemodynamic signature of flow diversion. Finite element analysis successfully reproduced the anticipated stiffness hierarchy (Steel > Nitinol > PLLA), with the trilayer polyurethane performing the closest to nitinol's elastic recovery characteristics.

The scaled specimens matched the native-scale stiffness within 2.3%. Predicted radial distension was several orders of magnitude lower than native wall values, confirming the validity of the rigid-wall computational fluid dynamics assumption. Stent-assisted diversion emerged as the most favorable hemodynamic profile among the examined strategies.

A stent with 50% porosity made of nitinol best matched the desired elastic mechanics, while a stent composed of 316L stainless steel offered the greatest resistance to radial compression.