Effect of Foam Insertion in Aneurysm Sac on Flow Structures in Parent Lumen: Relating Vortex Structures with Disturbed Shear

TL;DR

This study develops a methodology to analyze vortex structures in blood flow to understand how foam insertion in aneurysm sacs affects disturbed shear, which is linked to endothelial dysfunction.

Contribution

It introduces a vortex characterization approach using topological features to relate flow disturbances with aneurysm treatment effects.

Findings

Foam insertion increases the number of vortex core lines in the parent lumen.

Average length of vortex core lines increases significantly after foam insertion.

Regions with increased disturbed shear correlate with more oblique vortex core lines.

Abstract

Numerous studies suggest that disturbed shear, causing endothelium dysfunction, can be related to neighboring vortex structures. With this motivation, this study presents a methodology to characterize the vortex structures. Precisely, we use mapping and characterization of vortex structures' changes to relate it with the hemodynamic indicators of disturbed shear. Topological features of vortex core lines (VCLs) are used to quantify the changes in vortex structures. We use the Sujudi-Haimes algorithm to extract the VCLs from the flow simulation results. The idea of relating vortex structures with disturbed shear is demonstrated for cerebral arteries with aneurysms virtually treated by inserting foam in the sac. To get physiologically realistic flow fields, we simulate blood flow in two patient-specific geometries before and after foam insertion, with realistic velocity waveform imposed at the inlet, using the Carreau-Yashuda model to mimic the shear-thinning behavior. With homogenous porous medium assumption, flow through the foam is modeled using the Forcheimmer-Brinkmann extended Darcy model. Results show that foam insertion increases the number of VCLs in the parent lumen. The average length of VCL increases by 168.9% and 55.6% in both geometries. For both geometries under consideration, results demonstrate that the region with increased disturbed shear lies in the same arterial segment exhibiting an increase in the number of oblique VCLs. Based on the findings, we conjecture that an increase in oblique VCLs is related to increased disturbed shear at the neighboring portion of the arterial wall.