Retta El Sayed
BME PhD Proposal Presentation

Date:2022-04-13
Time: 09:00-11:00 AM
Location / Meeting Link: Emory University Hospital Conf. Room: D105A / https://emory.zoom.us/j/97060520747

Committee Members:
John N. Oshinski, Ph.D. (Advisor) Jason W. Allen, MD/Ph.D. (Co-Advisor) Shella D. Keilholz, Ph.D. David N. Ku, MD/Ph.D. Fadi Nahab, MD Lucas H. Timmins, Ph.D.


Title: 4D Flow Magnetic Resonance Imaging for the Study of Complex Blood Flow Patterns in Carotid Webs

Abstract: The most common cause of stroke is narrowing of blood vessels due to atherosclerotic plaque in the vessel wall. However, up to half of strokes have no known underlying cause (cryptogenic). Recently, carotid artery webs (CaWs), which appear as shelf-like projections into the vessel lumen in the proximal extracranial internal carotid artery (ICA), have been implicated as an etiology for stroke. CaWs may account for up to a third of cryptogenic strokes, generally in young patients without risk of cardiovascular disease. Patients with CaWs usually have a <50% narrowing in the ICA, however, they are suspected to have a higher stroke risk than atherosclerotic patients with similar percent stenosis. The major goal of this study is to understand complex blood flow patterns caused by CaWs. To achieve this goal, 4D Flow Magnetic Resonance Imaging sequence (4D Flow MRI) will be optimized for accurately quantifying blood flow metrics in a phantom model validated using computational fluid dynamics (CFD) simulations (Specific Aim 1). The optimization of 4D flow MRI using the CFD validation is essential due to the limited number of studies evaluating flow in the carotid artery using this imaging sequence and the lack of a gold standard. One of the most challenging tasks in quantifying local hemodynamics using 4D flow MRI is the low-quality magnitude image, limiting the information about vessel wall borders. Therefore, 4D flow MRI will be combined with a segmentation based on vessel wall imaging technique called 3D, stack-of-stars, multi-contrast atherosclerosis characterization (STAR-MATCH) imaging sequence to enhance wall detection (Specific Aim 2). Finally, this work proposes to evaluate pro-thrombogenic flow patterns in vivo, imaging patients with CaWs compared to patients with atherosclerosis lesions (with a similar degree of narrowing) and healthy volunteers using the optimized 4D Flow MRI sequence and post-processing pipeline developed in Specific Aims 1 and 2 (Specific Aim 3). This project aims to study local hemodynamic parameter effects in cases with complicated flow such CaW and atherosclerotic plaque using 4D flow MRI and CFD. The long-term goal of this work is to correlate hemodynamic flow metrics in ICA with CaWs to determine why patients with CaWs have a higher risk of thrombus formation than atherosclerotic patients with similar degrees of stenosis. Overall, this study will facilitate the use of non-invasive 4D flow MRI as a diagnostic tool to advance our understanding of pro-thrombogenic flow patterns in patients with complex hemodynamics related to a variety of etiologies and lay the groundwork for future studies that link hemodynamics to stroke risk.