Multi-time-lag PIV analysis of steady and pulsatile flows in a sidewall aneurysm

Abstract

The effect of inflow waveform on the hemodynamics of a real-size idealized sidewall intracranial aneurysm (IA) model was investigated using particle imaging velocimetry (PIV). For this purpose, we implemented an error analysis based on several PIV measurements with different time lags to ensure high precision of velocity fields measured in both the IA and the parent artery. The relative error measured in the main part of the circulating volume was \1 % despite the three orders of magnitude difference of parent artery and IA dome velocities. Moreover, important features involved in IA evolution were potentially emphasized from the qualitative and quantitative flow pattern comparison resulting from steady and unsteady inflows. In particular, the flow transfer in IA and the vortical structure were significantly modified when increasing the number of harmonics for a typical physiological flow, in comparison with quasi-steady conditions.

Computational fluid dynamics with stents: quantitative comparison with particle image velocimetry for three commercial off the shelf intracranial stents

“…The choice of such a simple IA geometry allows operating at nominal stent porosities, experimentally (for PIV) and virtually (for CFD). The recently developed MTL method, which uniformly reduces the experimental velocimetry precision below the 1% level,27 was very sensitive to CFD and PIV flow pattern differences, particularly for low velocity fields. The downward orientation of IA was essential for optical accessibility.…”

“…the geometry mismatch between actual IA geometry and silicone models was estimated with µCT to 102 µm 27. The influence of this mismatch accounted for up to 50% of CFD–PIV local velocity differences evaluated by NVD.…”

“…The sidewall IA geometry model (figure 1) considered for CFD and for molding of the silicone phantom was previously described by Bouillot et al 27. It is composed of a straight cylindrical tube of radius r=2 mm and a sphere of radius R=5 mm shifted downwards the artery centerline by a distance d 3 =6 mm.…”

“…The PIV experimental setup and MTL acquisition method were previously described by Bouillot et al 27. Considering optical accessibility, the IA model was oriented downwards.…”

“…To assess CFD performance in the presence of realistic stents, we performed high accuracy and uniform precision multi-time lag (MTL) PIV measurements27 28 in a sidewall IA model. For the three studied RS and FDS commercial off the shelf (COTS) stents, porosity and design parameters were assessed and correlated with CFD outcome.…”