A Magnetic Resonance Imaging Based Computational Analysis of Plaque Morphology and Hemodynamics in Patients with High Grade Asymptomatic Carotid Artery Stenosis

项目概要/摘要 颈内动脉（伊卡）狭窄是中风、长期残疾和死亡的主要原因。 目前伊卡狭窄的评估是基于通过双功超声（DUS）估计狭窄% 或横断面血管造影。里程碑式的研究表明，无症状的狭窄患者 >60%的病变应考虑颈动脉内膜切除术（CEA），然而， 保留给狭窄病变>80%和/或易损斑块的患者。仅狭窄百分比是一个很差的 斑块易损性的替代物，不能识别中风高危患者。此外，委员会认为， 狭窄的严重程度不能解释诸如斑块负荷，壁切应力（WSS）， 压力梯度和脑血流补偿，这是了解中风风险的关键。最优 颈动脉血运重建的患者选择，特别是无症状患者，仍然是一个问题。 重要的临床需求。 我们已经开发了一个基于MRI数据的患者特定CFD建模的工作流程， 并证明了具有相似狭窄程度的患者（使用DUS诊断的狭窄> 70%） 和/或横截面血管造影术）在压力梯度和脑血流方面具有差异。 这些结果再次表明，单独的解剖和血流数据不能识别中风风险的标志物 以及能从颈动脉血运重建中获益的患者。在本提案中，我们将利用MRI来 表征斑块成分和CFD建模，以评估斑块上的血流动力学负荷， 从而更好地评估脆弱性。我们假设相似程度的患者 无症状高度（DUS速度标准狭窄> 70%）颅外伊卡狭窄 在斑块形态、斑块上的血流动力学应力以及 脑灌注与其DUS速度曲线和狭窄严重程度无关。到 为了验证这一假设，我们将追求以下目标：1）使用T1/T2确定菌斑组成 使用MRI校准的CFD工作流程，在一个 无症状性伊卡狭窄患者队列， DUS. 2)描述上述指标的变异程度，从而测试 我们的假设3)在选择进行CEA的患者中，我们将研究 术前和术后血流动力学的差异，以评估手术的有效性 修复.

PROJECT SUMMARY/ABSTRACT Internal carotid artery (ICA) stenosis is a leading cause of stroke, long-term disability, and death. Current assessment of ICA stenosis is based on estimation of % stenosis via duplex ultrasound (DUS) or cross-sectional angiography. Landmark studies suggested that asymptomatic patients with stenotic lesions >60% should be considered for carotid endarterectomy (CEA), however intervention is often reserved to those with stenotic lesions >80% and/or vulnerable plaques. The % stenosis alone is a poor surrogate for plaque vulnerability and does not identify patients at high risk for stroke. Moreover, stenosis severity does not account for indices such as plaque burden, wall shear stress (WSS), pressure gradients, and cerebral flow compensation which are key to understand stroke risk. Optimal patient selection for carotid artery revascularization, particularly in asymptomatic patients, remains a significant clinical need. We have developed a workflow based on patient-specific CFD modeling informed by MRI data, and demonstrated that patients with similar degrees of stenosis (> 70% stenosis diagnosed using DUS and/or cross sectional angiography) have differences in pressure gradients and cerebral blood flow. These results suggest again that anatomic and flow data alone fail to identify markers for stroke risk and patients who would benefit from carotid revascularization. In this proposal, we will leverage MRI to characterize plaque composition and CFD modeling to assess hemodynamic loads on the plaque to thus provide a better assessment of vulnerability. We hypothesize that patients with similar degrees of asymptomatic high-grade (> 70% stenosis on DUS velocity criteria) extracranial ICA stenosis will have differences in plaque morphology, hemodynamics stresses on the plaque, and cerebral perfusion that are independent of their DUS velocity profiles and stenosis severity. To test this hypothesis, we will pursue the following Aims: 1) To determine plaque composition using T1/T2 MRI, hemodynamic loads on the plaque and cerebral flow using MRI-calibrated CFD workflows in a cohort of patients with asymptomatic high grade ICA stenosis who have similar velocity profiles on DUS. 2) To characterize the degree of variability in the above metrics, and therefore test the validity of our hypothesis. 3) In a subset of the patients who are chosen for CEA, we will investigate the differences in pre-operative and post-operative hemodynamic to assess the efficacy of the surgical repair.