Comparison of CFD and MRI Flow and Velocities in an In Vitro Large Artery Bypass Graft Model

Abstract

Bypass graft failures have been attributed to various hemodynamic factors, including flow stasis and low shear stress. Ideally, surgeries would minimize the occurrence of these detrimental flow conditions, but surgeons cannot currently assess this. Numerical simulation techniques have been proposed as one method for predicting changes in flow distributions and patterns from surgical bypass procedures, but comparisons against experimental results are needed to assess their usefulness. Previous in vitro studies compared simulated results against experimentally obtained measurements, but they focused on peripheral arteries, which have lower Reynolds numbers than those found in the larger arteries. In this study, we compared simulation results against measurements obtained using magnetic resonance imaging (MRI) techniques for a phantom model of a stenotic vessel with a bypass graft under conditions suitable for surgical planning purposes and with inlet Reynolds numbers closer to those found inthe larger arteries. Comparisons of flow rate and velocity profiles were performed at maximum and minimum flows at four locations and used simulation results that were temporally and spatially averaged, key postprocessing when comparing against phase contrast MRI measurements. The maximum error in the computed volumetric flow rates was 6% of the measured values, and excellent qualitative agreement was obtained for the through-plane velocity profiles in both magnitude and shape. The in-plane velocities also agreed reasonably well at most locations.

In Vivo Wall Shear Stress Distribution in the Carotid Artery

“…15,18,38 -40 However, it is still debated how boundary conditions needed for the CFD calculations (rigid walls, idealized in-flow velocity profiles, non-Newtonian blood models) affect the results. [41][42][43] CFD can provide vital information about the effect of 3D vascular geometry on flow and wall parameters as shown in a systematic and detailed analysis of 50 normal carotid bifurcations in a study by Lee at al. 18 In their study, a similar data analysis strategy based on 20% and 10% group thresholds was used.…”

Combinational Optimization of Strut Placement for Intracranial Stent Using a Realistic Aneurysm

“…Reynolds number of 200 was chosen to compare the flow to our previous study using same aneurysm. Given that the Reynolds number ranges from 110 to 850, a non-Newtonian effect can be neglected [20]. In this study, we used a basilar artery with a diameter of 3.9 mm and the Reynolds number of 200.…”

The emerging clinical role of cardiovascular magnetic resonance imaging

“…Several methods are available for this purpose -phase-contrast sequences quantify anterograde and retrograde flow volumes and velocities in any desired imaging plane, within a vessel or a valvular plane (89,90). The accuracy of phase-contrast measurements as assessed with in vitro models is excellent (91,92) and good correlations have been documented between CMR flow measurements and Doppler echocardiography (93), as well as cardiac catheterization (94,95). Cine imaging is applied to quantify the orifice of a stenotic valve (96).…”