Hemodynamic characteristics and drug deposition in cerebral aneurysm sac.

Abstract

Patient-specific cerebral aneurysms exhibit complex hemodynamics insights that influence thrombus formation, wall remodeling, and therapeutic delivery. The article presents a high-fidelity, multi-parametric CFD analysis of nine distinct aneurysm cases using 3-D model-resolved meshes, non-Newtonian Casson rheology, and steady-state flow conditions. Further, the Lagrangian particle tracking was employed to assess drug transport and hemodynamic metrics such as WSS and normalized residence time (NRT) were evaluated, along with vortex dynamics, indicators including helicity (H) and Q criterion to characterize rotational flow structures. Results reveal that narrowed neck models (m₁, m₂, m₅, m₈) exhibit weak vortex structures and dominant axial washout (velocity magnitude < 0.10 m/s; NRT < 0.2), while sac-expanded geometries (m₃, m₄, m₆, m₉) support robust helical vortices (H > 40 m²/s², Q > 0) and elevated residence times. Regions of low WSS (τ_w < 0.5 Pa) spatially co-localize with high NRT and potential thrombogenicity, whereas high WSS (τ_w > 2.5 Pa) associates with jet impingement zones and possible endothelial damage. Notably, sharp WSS gradients are identified as destabilizing hemodynamic factors. Rheological analysis reveals a critical threshold at γ̇ ≈ 415 s⁻¹ (µ ≈ 6.4 mPa·s), distinguishing thrombosis-prone regions (low γ̇, high µ) from stable zones (high γ̇, low µ). Particle transport studies show that effective drug retention occurs in high-helicity, wide neck models for Stokes number (St = 0.1-1), while laminar-dominant aneurysmal flows demonstrate poor drug deposition due to axial convection. Overall, the findings underscore that aneurysm stability and therapeutic outcomes are governed by the interplay of aneurysm induced flow structures, WSS heterogeneity, non-Newtonian rheology, and vortex coherence are refining rupture risk assessments and optimizing endovascular drug delivery strategies.