A magnetic resonance imaging-based computational analysis of cerebral hemodynamics in patients with carotid artery stenosis

Figure 1. 3D-reconstructed anatomical models. (A) Close-up of the stenosed carotid bifurcations of patients 1 and 2. The red arrows indicate the location of maximum stenosis. An axial cross-section illustrates the comparison between image data and model contours. (B) Posterior view of the CoW. The black arrows indicate variations in the CoW anatomy. R and L indicate the right and left sides from the subject’s perspective. RICA, right internal carotid artery; RECA, right external carotid artery; LICA, left internal carotid artery; LECA, left external carotid artery; CoW, Circle of Willis; CTA, computed tomography angiography; DUS, Duplex ultrasound.

Figure 2. MRI-informed CFD flow and pressure waveforms at selected locations above the carotid bifurcation and in the CoW over a full cardiac cycle. MRI-informed CFD flow waveforms in the cervical arteries are compared to in-vivo PC-MRI flow data. (A) Pre-operative model of patient 1 (B) Pre-operative model of patient 2. RMCA, right middle cerebral artery; RACA, right anterior cerebral artery; RICA, right internal carotid artery; RVA, right vertebral artery; LACA, left anterior cerebral artery; LMCA, left middle cerebral artery; LVA, left vertebral artery; LICA, left internal carotid artery; MRI, magnetic resonance imaging; CFD, computational fluid dynamics; PC-MRI, phase-contrast MRI; CoW, circle of Willis.

Figure 3. Analysis of blood supply in the CoW with Lagrangian particle tracking. Particles are color-coded based on the originating cervical artery. Histograms show the particle count over a full cardiac cycle at each outlet. The accuracy of the MRI-informed CFD models was demonstrated by validating the supply of the intracranial arteries obtained from LPT against territorial perfusion from vessel-selective ASL, which resulted in an overall good qualitative match. A more comprehensive and quantitative validation of the patient models was previously presented (19). LACA, left anterior cerebral artery; RACA, right anterior cerebral artery; LMCA, left middle cerebral artery; RMCA, right middle cerebral artery; LPCA, left posterior cerebral artery; RPCA, right posterior cerebral artery; RICA, right internal carotid artery; LICA, left internal carotid artery; RVA, right vertebral artery; LVA, left vertebral artery; Cow, circle of Willis; MRI, magnetic resonance imaging; CFD, computational fluid dynamics; LPT, Lagrangian particle tracking; ASL, arterial spin labeling.

Figure 4. Comparison of the preoperative and postoperative blood supply in the CoW of patient 2 using Lagrangian particle tracking. Particles are color-coded based on the originating cervical artery. Histograms show the particle count over a full cardiac cycle at the right and left ACA. A close-up shows the flow in the anterior communication artery. LACA, left anterior cerebral artery; RACA, right anterior cerebral artery; RICA, right internal carotid artery; LICA, left internal carotid artery; LVA, left vertebral artery; Cow, circle of Willis; ACA, anterior cerebral artery.

Figure 5. Comparison of preoperative and postoperative mean flow rates in the main arteries of patient 2. Mean flow rates were normalized by the CO. CO, cardiac output; LICA, left internal carotid artery; RICA, right internal carotid artery; LVA, left vertebral artery; RVA, right vertebral artery; LACA, left anterior cerebral artery; RACA, right anterior cerebral artery; LMCA, left middle cerebral artery; RMCA, right middle cerebral artery; LPCA, left posterior cerebral artery; RPCA, right posterior cerebral artery; LSCA, left superior cerebral artery; RSCA, right superior cerebral artery.

Figure 6. Evaluation of the mean pressure gradient ΔP¯ over the stenosis in patients 1 and 2. The pressure distribution in the vasculature is shown at peak systole. ΔP¯ was calculated as the difference between the mean pressures 2 cm proximal and distal to the peak stenosis. RICA, right internal carotid artery; LICA, left internal carotid artery.