Assessment of turbulent blood flow and wall shear stress in aortic coarctation using image-based simulations

Abstract

In this study, we analyzed turbulent flows through a phantom (a 180$$^{\circ }$$ ∘ bend with narrowing) at peak systole and a patient-specific coarctation of the aorta (CoA), with a pulsating flow, using magnetic resonance imaging (MRI) and computational fluid dynamics (CFD). For MRI, a 4D-flow MRI is performed using a 3T scanner. For CFD, the standard $$k-\epsilon $$ k - ϵ , shear stress transport $$k-\omega $$ k - ω , and Reynolds stress (RSM) models are applied. A good agreement between measured and simulated velocity is obtained for the phantom, especially for CFD with RSM. The wall shear stress (WSS) shows significant differences between CFD and MRI in absolute values, due to the limited near-wall resolution of MRI. However, normalized WSS shows qualitatively very similar distributions of the local values between MRI and CFD. Finally, a direct comparison between in vivo 4D-flow MRI and CFD with the RSM turbulence model is performed in the CoA. MRI can properly identify regions with locally elevated or suppressed WSS. If the exact values of the WSS are necessary, CFD is the preferred method. For future applications, we recommend the use of the combined MRI/CFD method for analysis and evaluation of the local flow patterns and WSS in the aorta.

On the identification of hypoxic regions in subject-specific cerebral vasculature by combined CFD/MRI

“…While the absolute values of WSS are generally underestimated by MRI, the local distributions of high/low WSS can still be properly estimated by this technique [ 19 ]. To be able to compare the WSS distribution between CFD and MRI, we have normalized both of the datasets by their respective average values.…”

“…To be able to compare the WSS distribution between CFD and MRI, we have normalized both of the datasets by their respective average values. This allows for a qualitative comparison between the two methods [ 19 ]. As shown in figure 4 , the local WSS distribution in the different arteries of CoW is similar for MRI and CFD.…”

“…In recent years, a continuous increase in computational capabilities enabled detailed numerical simulation studies of the blood flow in the complex patient-specific geometries of the cardiovascular system. To obtain subject-specific results, the four-dimensional (4D)-flow MRI measurements can be used to provide both computational domain and boundary conditions for CFD simulations [9][10][11][12][13][14][15][16][17][18][19]. In addition to the flow, the mass transfer needs to be modelled too.…”

Does the Internal Carotid Artery Attenuate Blood‐Flow Pulsatility in Small Vessel Disease? A 7 T 4D‐Flow MRI Study

“…18 The interexamination, interobserver reproducibility, and intraobserver repeatability of the analysis with the CAAS software have been tested previously and showed a very good reproducibility and repeatability for volume, surface area, and centerline length (ICC = 0.65-0.96) and excellent reproducibility and repeatability for maximal diameter (ICC = 0.94-0.99). [20][21][22] For the current study, we assessed the intraobserver repeatability (RvT with 3 years of experience with MRI flow data analysis, including CAAS software) by analyzing five subjects twice. The results showed an average dice coefficient of 0.94 (range 0.90-0.98) for vPI, mean velocity, diameter, and arterial distensibility.…”

Accelerated sequences of 4D flow MRI using GRAPPA and compressed sensing: A comparison against conventional MRI and computational fluid dynamics

“…CFD coupled to MRI has already proven capable of providing the flow fields with high fidelity under well‐controlled in vitro conditions, 23 , 24 whereas moderate correlations have been reported for patient‐specific MRI‐based simulations 25 , 26 or superresolution of 4D flow MRI using CFD 27 for velocity and flow rates. Indeed, the choice of the CFD strategy is crucial to accurately predict the hemodynamics, particularly in such flow regimes where boundary conditions 28 and turbulence models, 29 , 30 as well as numerical schemes , 31 have shown to greatly influence the resulting flow field. In this context, CFD may be used as a third‐party modality, yet without being considered a ground truth, to confirm and quantify the discrepancies observed with 4D flow MRI.…”