Sensitivity of CFD Based Hemodynamic Results in Rabbit Aneurysm Models to Idealizations in Surrounding Vasculature

Abstract

Computational fluid dynamics (CFD) studies provide a valuable tool for evaluating the role of hemodynamics in vascular diseases such as cerebral aneurysms and atherosclerosis. However, such models necessarily only include isolated segments of the vasculature. In this work, we evaluate the influence of geometric approximations in vascular anatomy on hemodynamics in elastase induced saccular aneurysms in rabbits. One representative high aspect ratio (AR—height/neck width) aneurysm and one low AR aneurysm were created at the origin of the right common carotid artery in two New Zealand white rabbits. Three-dimensional (3D) reconstructions of the aneurysm and surrounding arteries were created using 3D rotational angiographic data. Five models with varying extents of neighboring vasculature were created for both the high and low AR cases. A reference model included the aneurysm sac, left common carotid artery (LCCA), aortic arch, and downstream trifurcation/quadrification. Three-dimensional, pulsatile CFD studies were performed and streamlines, wall shear stress (WSS), oscillatory shear index, and cross sectional velocity were compared between the models. The influence of the vascular domain on intra-aneurysmal hemodynamics varied between the low and high AR cases. For the high AR case, even a simple model including only the aneurysm, a small section of neighboring vasculature, and simple extensions captured the main features of the steamline and WSS distribution predicted by the reference model. However, the WSS distribution in the low AR case was more strongly influenced by the extent of vasculature. In particular, it was necessary to include the downstream quadrification and upstream LCCA to obtain good predictions of WSS. The findings in this work demonstrate the accuracy of CFD results can be compromised if insufficient neighboring vessels are included in studies of hemodynamics in elastase induced rabbit aneurysms. Consideration of aspect ratio, hemodynamic parameters of interest, and acceptable magnitude of error when selecting the vascular domain will increase reliability of the results while decreasing computational time.

From bench to bedside: utility of the rabbit elastase aneurysm model in preclinical studies of intracranial aneurysm treatment

“…In a study of 51 elastase induced RCCA aneurysms, Zeng et al found that the range in values of pressure, wall shear stress, and oscillatory shear index were all within the ranges seen in human aneurysms. The number of recirculation regions seen within the aneurysms was also similar to that seen in human aneurysms 31 32…”

High WSS or Low WSS? Complex Interactions of Hemodynamics with Intracranial Aneurysm Initiation, Growth, and Rupture: Toward a Unifying Hypothesis

“…Animal models commonly used for clinical studies are good for testing medical devices and investigating hemodynamics 71 but are generally biologically deficient. On the other hand, current endogenous models 34,37 capture some hemodynamic-biologic effects in the early stages of aneurysm formation but lack the ability to study growth and rupture.…”

Biomechanical Factors Influencing Type B Thoracic Aortic Dissection: Computational Fluid Dynamics Study

“…Suspended particles and nonNewtonian effect of the fluid were ignored. The vessel walls were taken as rigid, an assumption frequently employed in CFD analysis of blood flow (Shojima et al, 2004;Zeng et al, 2010). Effects of relaxing these assumptions can be investigated, e.g.…”

“…Consequently, quantitative information is provided to the clinicians to assess if such a repair is necessary. The precise selection of vasculature geometry is critical, as computational accuracy might be compromised if insufficient neighboring blood vessels are included in the calculations (Zeng et al, 2010). Here we tested the robustness of our results against variation in domain geometry in two ways.…”