4D Flow Magnetic Resonance Imaging and Computational Fluid Dynamics for the Study of Complex Blood Flow Patterns in Carotid Webs

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ELSAYED-DISSERTATION-2024.pdf (30.27 MB)
4DFlowMRI.mp4 (12.35 MB)
CFDSimulation.mp4 (10.23 MB)
Author(s)
El Sayed, Retta
Advisor(s)
Allen, Jason W.
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Wallace H. Coulter Department of Biomedical Engineering
The joint Georgia Tech and Emory department was established in 1997
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https://hdl.handle.net/1853/75300
Abstract
Carotid webs (CaW) contribute to cryptogenic strokes in young patients aged 30-48 years, even in the absence of traditional risk factors for vascular disease. CaW poses a challenge in clinical management as it is often resistant to traditional antiplatelet therapy. Understanding the complex flow alterations induced by CaW that lead to thrombus formation and subsequent stroke is crucial to improve clinical outcomes. To characterize flow patterns associated with CaW, advanced imaging techniques such as three-dimensional, three-directional, ECG-gated, time-resolved, phase-contrast magnetic resonance imaging (4D flow MRI) as well as computational fluid dynamics (CFD) are employed in this study. First, the spatio-temporal parameters of 4D flow magnetic resonance imaging were optimized using a patient-derived phantom model and CFD. This optimization is crucial for resolving complex flow patterns in the regions immediately distal to CaW within a clinically acceptable scan time. Subsequently, the study enrolled participants to measure hemodynamics in the carotid artery bulb in three groups: patients with CaW, patients with mild atherosclerosis with a comparable degree of narrowing, and healthy subjects. This was achieved using both 4D flow MRI and CFD. The results suggest that CaW is associated with lower time-averaged wall shear stress (TAWSS) and higher oscillatory shear index (OSI) than both mild atherosclerosis and carotid bifurcations in healthy subjects. Finally, we used a dataset where subjects had images with and without a clot to determine hemodynamic metrics in the location where a thrombus was observed in patients with CaW. This enables us to identify patients with CaW at risk for stroke by pinpointing the shear rate responsible for thrombus formation downstream of regions with blood stasis. This research aimed to deepen our understanding of the hemodynamic mechanisms linked to stroke risk in patients with CaW. These insights may lead to enhanced diagnostic and preventive strategies tailored to subjects with CaW, potentially improving outcomes.
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2024-04-29
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Dissertation
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