Hemodynamic and inflammatory imaging in evaluation of abdominal aortic aneurysms

描述(申请人提供)：腹主动脉瘤(AAA)是常见的，如果进展到破裂可能危及生命。据报道，5%的老年男性患有这种疾病，每年有超过15,000人死于此病。血管基本尺寸是目前临床上用于对患者进行风险分层的主要影像测量方法。但除了维度，故事中还有更多的东西。用计算模型估计的壁应力可能比直径更好地预测生长和破裂。增长往往不是连续的，而是以快速增长和随后的停滞为标志。小系列报道，不相关的外科手术可导致腹主动脉破裂。这些发现表明，间歇性和异质性炎症过程与不利的血流动力学相一致，对于AAA疾病的进展是重要的。与传统的解剖分析相比，新的功能成像技术能更全面地揭示主动脉疾病的复杂性。虽然AAA已经得到了广泛的研究，但疾病进展的机制还没有完全阐明。如果更好地了解，小AAA(5.5 cm)患者的管理可以得到显著改善。这些动脉瘤中的许多可以通过长达2-3年的长时间筛查得到安全的随访，但也有一些可能进展为破裂。确定这一亚组将极大地简化数百万AAA患者的监视成像。另一方面，大多数AAA从不破裂，识别低风险患者可以帮助更好地管理资源，并仅对那些真正风险较高的患者进行干预。主动脉壁发炎可以 用核磁共振造影剂阿魏酸甲酯进行评价，阿魏酸甲酯在延迟成像中具有巨噬细胞选择性。MRI还提供了对主动脉血流动力学的独特和全面的评估。使用时间分辨的3D相位对比MRI(4D FLOW)的血流成像可以量化关键的二次血管参数，包括湍流和壁切应力(WSS)。用模拟回声(密集)进行电影位移编码可以量化血管壁所经历的区域拉伸差异。基于MRI体积数据的计算模型可用于计算壁应力。我们研究的目标是发现重要的炎症变化和不良血流动力学，这些都是目前的成像没有解决的，并用它们来预测疾病的进展。我们寻求有意义地推进对未达到当前干预阈值的患者的风险评估，并通过完善监测成像方案和关于AAA早期干预的决定来改善结果。

DESCRIPTION (provided by applicant): Abdominal aortic aneurysms (AAA) are common and can be life-threatening if they progress to rupture. They have been reported in 5% of older men and account for over 15,000 deaths per year. Basic vessel dimensions are currently the primary imaging measurement used clinically to risk-stratify patients. But there is more to the story than dimensions. Wall stress estimated with computational modeling may better predict growth and rupture than diameters. Growth is often not continuous, and instead marked by periods of rapid growth followed by quiescence. Small series report that unrelated surgical procedures can precipitate AAA rupture. These findings suggest that episodic and heterogeneous inflammatory processes in concert with adverse hemodynamics are important for the progression of AAA disease. The complexity of aortic disease is more fully revealed with new functional imaging techniques than with conventional anatomic analysis alone. While AAA has been extensively studied, the mechanisms of disease progression have not been fully elucidated. If better understood, the management of patients with small AAAs (< 5.5cm) could be significantly improved. Many of these aneurysms can be followed safely with a long screening interval of 2-3 years, but some may progress to rupture. Identifying this subset would greatly streamline the surveillance imaging of the millions of patients with AAA. On the other hand, the majority of AAAs never rupture, and identifying low risk patients could help better manage resources and subject only those patients at truly elevated risk to intervention. Aortic wall inflammation can be evaluated with the MRI contrast agent ferumoxytol, which has macrophage- selective properties on delayed imaging. MRI also offers a unique and comprehensive assessment of aortic hemodynamics. Blood flow imaging with time-resolved, 3D phase-contrast MRI (4D Flow) allows quantification of key secondary vascular parameters including turbulence and wall shear stress (WSS). Cine Displacement Encoding with Stimulated Echos (DENSE) can quantify regional stretch differences experienced by the vessel wall. Computational modeling based on MRI volumetric data can be used to calculate wall stress. The goal of our study is to uncover important inflammatory changes and adverse hemodynamics that are not addressed with current imaging, and use them to predict disease progression. We seek to meaningfully advance the assessment of risk in patients who do not meet current intervention thresholds and improve outcomes by refining surveillance imaging regimens and decisions regarding early intervention for AAAs.