CFD: Computational Fluid Dynamics or Confounding Factor Dissemination? The Role of Hemodynamics in Intracranial Aneurysm Rupture Risk Assessment

Abstract

SUMMARY:Image-based computational fluid dynamics holds a prominent position in the evaluation of intracranial aneurysms, especially as a promising tool to stratify rupture risk. Current computational fluid dynamics findings correlating both high and low wall shear stress with intracranial aneurysm growth and rupture puzzle researchers and clinicians alike. These conflicting findings may stem from inconsistent parameter definitions, small datasets, and intrinsic complexities in intracranial aneurysm growth and rupture. In Part 1 of this 2-part review, we proposed a unifying hypothesis: both high and low wall shear stress drive intracranial aneurysm growth and rupture through mural cell-mediated and inflammatory cell-mediated destructive remodeling pathways, respectively. In the present report, Part 2, we delineate different wall shear stress parameter definitions and survey recent computational fluid dynamics studies, in light of this mechanistic heterogeneity. In the future, we expect that larger datasets, better analyses, and increased understanding of hemodynamicbiologic mechanisms will lead to more accurate predictive models for intracranial aneurysm risk assessment from computational fluid dynamics. ABBREVIATIONS:CFD ϭ computational fluid dynamics; IA ϭ intracranial aneurysm; LSA ϭ low shear-stress area; MWSS ϭ maximum wall shear stress; OSI ϭ

The Computational Fluid Dynamics Rupture Challenge 2013—Phase I: Prediction of Rupture Status in Intracranial Aneurysms

“…Both studies agreed that ruptured aneurysms present complex flow structures and concentrated inflow. Recently, Meng et al 12 and Xiang et al 13 published a 2-part review summarizing the various criteria for rupture status predictions and introducing a hypothesis that both high and low WSS might lead to aneurysm rupture.…”

Changes of Time-Attenuation Curve Blood Flow Parameters in Patients with and without Carotid Stenosis

“…[1][2][3] Using different approaches, a number of recent studies have demonstrated the feasibility of quantitative flow parameter measurement by using flat detector DSA. [4][5][6][7] Compared with optical flow methods and computer fluid dynamics simulations, flow parameter analysis with the time-attenuation curve (TDC) of DSA images is less demanding in terms of computer power and processing time. 8,9 Clinically, TDCs are used to assess the "real-time" peritherapeutic hemodynamics of various vascular disorders in an angiography suite.…”

Variability of hemodynamic parameters using the common viscosity assumption in a computational fluid dynamics analysis of intracranial aneurysms

“…Large discrepancies were observed between the results with the non-Newtonian model with higher viscosity and those with the Newtonian model for several parameters, especially MWSS and NWSS, where NWSS is the WSS value normalized by WSS on the parent artery. Data are typically normalized so that the results for different patients can be compared when a CFD analysis is performed using the same inflow conditions [27]. Our results show that the differences in the ratios between the Newtonian and non-Newtonian models were greater for the normalized WSS than for the non-normalized WSS in case A (the smallest aneurysm).…”