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. 2018 May;8(4):399-409.
doi: 10.21037/qims.2018.05.02.

Hemodynamic analysis of carotid artery after endarterectomy: a preliminary and quantitative imaging study based on computational fluid dynamics and magnetic resonance angiography

Yuanyuan Dai  1   2 , Peng Lv  1 , Ashkan Javadzadegan  2 , Xiao Tang  3 , Yi Qian  2 , Jiang Lin  1
Affiliations

Hemodynamic analysis of carotid artery after endarterectomy: a preliminary and quantitative imaging study based on computational fluid dynamics and magnetic resonance angiography

Yuanyuan Dai et al. Quant Imaging Med Surg. 2018 May.

Abstract

Background: The carotid blood flow following carotid endarterectomy (CEA) is not fully understood. Computational fluid dynamics (CFD) is a promising method to study blood flow. This study is to investigate local hemodynamic characteristics after CEA via the use of unenhanced magnetic resonance angiography (MRA) and CFD.

Methods: Eight carotid arteries with atherosclerosis and sixteen normal carotid arteries were included in this study. Time-of-flight (TOF) and phase contrast (PC) MRA were applied for the measurement of three-dimensional artery geometries and velocity profile under CFD simulation. The hemodynamic parameters of the proximal internal carotid artery (ICA) including velocity, ICA/common carotid artery (CCA) velocity ratio, mean, maximum, minimum and gradient of wall shear stress (WSSmean, WSSmax, WSSmin and WSSG) were calculated before and after CEA. Morphologic characteristics of the carotid including bifurcation angle, tortuosity and planarity were also analyzed.

Results: Compared with pre-CEA, there was a significant reduction in post-CEA velocity, WSSmax, WSSmean, and WSSG, by 87.24%±13.38%, 86.86%±14.97%, 57.32%±56.71% and 69.74%±37.03% respectively, whereas WSSmin was almost unchanged. ICA/ CCA velocity ratios increased significantly after CEA. We also found that the post-CEA flow conditions were positively remodelled to approximate the conditions in normal arteries. The correlation between PC-MRA and CFD was excellent for the measurement of maximum velocity at the external carotid artery (r=0.846).

Conclusions: Our preliminary results indicated that major flow dynamics were restored shortly following CEA, and CFD based on MRA measurements could be useful for quantitative evaluation of hemodynamic outcomes after CEA.

Keywords: Carotid atherosclerosis; computational fluid dynamics (CFD); magnetic resonance angiography (MRA); wall shear stress (WSS).

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Conflict of interest statement

Conflicts of Interest: The authors have no conflicts of interest to declare.

Figures

Figure 1
Figure 1
3D TOF-MRA images generated from pre-CEA (A), post-CEA (B) and normal carotids (C). Pre- and post-CEA carotids are from a 59-year-old male with severe stenosis at the proximal internal carotid artery 3 days before and 5 days after CEA. The normal carotid is from a 48-year-old healthy male. TOF-MRA, time-of-flight magnetic resonance angiography; CEA, carotid endarterectomy.
Figure 2
Figure 2
Velocities measured by PC-MRA. (A,B,C) Show velocities from CCA (A), ICA (B) and ECA (C) of a pre-CEA carotid (the same artery as Figure 1A). The velocities of the post-CEA carotid (the same artery as Figure 1B) in CCA (D), ICA (E) and ECA (F) are shown. The velocities of a normal carotid (the same artery as Figure 1C) measured in CCA (G), ICA (H) and ECA (I) are demonstrated. PC-MRA, phase contrast magnetic resonance angiography; CCA, common carotid artery; ICA, internal carotid artery; ECA, external carotid artery; CEA, carotid endarterectomy.
Figure 3
Figure 3
Scatter plots show the hemodynamic parameters of velocity (A), ICA/CCA velocity ratio (B), WSSmax (C), WSSG (D), WSSmean (E) and WSSmin (F) from eight stenotic carotids before and after CEA and sixteen normal carotids (control). ICA, internal carotid artery; CCA, common carotid artery; CEA, carotid endarterectomy; WSS, wall shear stress.
Figure 4
Figure 4
Wall shear stress map showed that the distribution of wall shear stress was demonstrated on a pre-CEA (A), post-CEA (B) and normal carotid (C). Wall shear stress increases significantly at stenotic area of pre-CEA carotid. In contrast, the wall shear stress profile after CEA from the same patient is similar to that of a normal carotid. CEA, carotid endarterectomy.
Figure 5
Figure 5
Wall shear stress map demonstrated that (A) the carotid with large tortuosity showed relatively low wall shear stress at bifurcation area (circle), while the carotid with small tortuosity showed relatively high wall shear stress at bifurcation (B).
Figure 6
Figure 6
There is an excellent agreement between CFD and PC-MRA in measurement of the velocity at external carotid artery. CFD, computational fluid dynamics; PC-MRA, phase contrast magnetic resonance angiography.
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