Validation of CFD simulations of cerebral aneurysms with implication of geometric variations

Background. Computational fluid dynamics (CFD) simulations using medical-image-based anatomical vascular geometry are now gaining clinical relevance. This study aimed at validating the CFD methodology for studying cerebral aneurysms by using particle image velocimetry (PIV) measurements, with a focus on the effects of small geometric variations in aneurysm models on the flow dynamics obtained with CFD. Method of Approach. An experimental phantom was fabricated out of silicone elastomer to best mimic a spherical aneurysm model. PIV measurements were obtained from the phantom and compared with the CFD results from an ideal spherical aneurysm model (S1). These measurements were also compared with CFD results, based on the geometry reconstructed from three-dimensional images of the experimental phantom. We further performed CFD analysis on two geometric variations, S2 and S3, of the phantom to investigate the effects of small geometric variations on the aneurysmal flow field. Results. We found poor agreement between the CFD results from the ideal spherical aneurysm model and the PIV measurements from the phantom, including inconsistent secondary flow patterns. The CFD results based on the actual phantom geometry, however, matched well with the PIV measurements. CFD of models S2 and S3 produced qualitatively similar flow fields to that of the phantom but quantitatively significant changes in key hemodynamic parameters such as vorticity, positive circulation, and wall shear stress. Conclusion. CFD simulation results can closely match experimental measurements as long as both are performed on the same model geometry. Small geometric variations on the aneurysm model can significantly alter the flow-field and key hemodynamic parameters. Since medical images are subjected to geometric uncertainties, image-based patient-specific CFD results must be carefully scrutinized before providing clinical feedback

Degree of Retrograde Flow and Its Effect on Local Hemodynamics and Plaque Distribution in an Aortic Regurgitation Murine Model of Atherosclerosis

INTRODUCTION Previously, Zhou et al. Recently, Hoi et al. [2] used image-based Computational Fluid Dynamics (CFD) to demonstrate that maps of oscillatory shear index (OSI) and relative residence time (RRT) METHODS As detailed in [2] , the three-dimensional (3D) aortic geometry of a control mouse was reconstructed from micro-CT scans. The smoothed model, which closely resembled the original aortic lumen, was truncated at the celiac artery, thereby including only the aortic arch and DTA

Carotid bifurcation hemodynamics in older adults: effect of measured versus assumed flow waveform

Recent work has illuminated differences in carotid arter

A model system for mapping vascular responses to complex hemodynamics at arterial bifurcations in vivo

Cerebral aneurysms are preferentially located at arterial bifurcation apices with complex hemodynamics. To understand disease mechanisms associated with aneurysm initiation, we attempted to establish a causal relationship between local hemodynamics and vascular responses. Arterial bifurcations were surgically created from native common carotid arteries in two dogs, angiographically imaged 2 weeks and 2 months later, and then excised. We characterized local morphological changes in response to specifically manipulated hemodynamics. Computational fluid dynamics simulations were performed on the in vivo images and results mapped onto histological images. Local flow conditions, such as high wall shear stress and high wall shear stress gradient, were found to be associated with vascular changes, including an intimal pad in the flow impingement region and a "groove" bearing the characteristics of an early aneurysm. This novel method of histohemodynamic micromapping reveals a direct correlation between an altered hemodynamic microenvironment and vascular responses consistent with aneurysm development