Advanced MRI Evaluation of Abdominal Aortic Aneurysms

腹主动脉瘤（AAA）是常见的，如果进展到破裂，可能危及生命。他们 据报道，在8%的老年男性中，每年有超过15，000人死亡。基本血管 尺寸是目前临床上用于对患者进行风险分层的主要成像测量。但 比维度更重要的东西用计算生物力学模型估计的壁应力可以 比直径更好地预测生长和破裂。此外，AAA级增长往往不是连续的， 而是以快速增长和随后的停滞为特征。小系列报道称， 手术可促使AAA破裂，表明偶发性和异质性炎症过程 与不利的血流动力学和生物力学相一致，对AAA疾病的进展很重要。 新的功能成像技术比传统的血管造影技术更能充分揭示主动脉疾病的复杂性。 传统的解剖分析。虽然AAA已被广泛研究，但疾病的机制 进展尚未完全阐明。如果能更好地理解，它们可能会大大改善 小AAA（<5.5 cm）的退伍军人的管理。许多这样的动脉瘤可以安全地随访 筛查间隔时间较长，为2 - 3年，但有些可能进展为破裂。识别这个子集将 极大地简化了对患有AAA的退伍军人的监视成像。另一方面，大多数AAA 永远不会破裂，识别低风险退伍军人可以帮助更好地管理资源， 退伍军人面临的干预风险真的很高。 MRI独特地提供了对作用于血管壁的力的全面评估（血流动力学和 生物力学），以及影响壁强度的因素（结构、形态和炎症）。血流 使用时间分辨3D相位对比MRI（4D Flow）成像可量化关键参数，包括 流动湍流和壁面切应力。动态对比增强（DCE）MRI可以提供有效的评估， 主动脉壁炎症刺激回波电影位移编码（DENSE）MRI可以量化 血管壁经历的局部拉伸差异，以及与3D容积MRI解剖学 数据和计算建模可用于计算患者特异性机械壁应力。 我们研究的目的是揭示重要的炎症变化和不良血流动力学， 生物力学，目前的成像没有解决，并使用它们来预测AAA疾病的进展。 我们还试图优化一个短（5分钟）的MRI协议，没有对比，以确定是否有附加值 对于这种综合评估，快速非造影MRI更可取，更有效地使用VA 资源我们的总体目标是有意义地推进风险评估的退伍军人谁不符合 当前的干预阈值，从而在未来通过改进监测成像来改善结果 关于AAAs早期干预的方案和决定。

Abdominal aortic aneurysms (AAA) are common and can be life-threatening if they progress to rupture. They have been reported in up to 8% 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 biomechanical modeling may better predict growth and rupture than diameters. Furthermore, AAA 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, suggesting that episodic and heterogeneous inflammatory processes in concert with adverse hemodynamics and biomechanics 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, they could lead to significant improvement of the management of veterans with small AAAs (< 5.5 cm). 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 veterans with AAA. On the other hand, the majority of AAAs never rupture, and identifying low risk veterans could help better manage resources and subject only those veterans at truly elevated risk to intervention. MRI uniquely offers comprehensive assessment of forces acting on the vessel wall (hemodynamics and biomechanics), as well as factors affecting wall strength (structure, morphology and inflammation). Blood flow imaging with time-resolved 3D phase-contrast MRI (4D Flow) allows quantification of key parameters including flow turbulence and wall shear stress. Dynamic contrast enhanced (DCE) MRI may offer efficient evaluation of aortic wall inflammation. Cine Displacement Encoding with Stimulated Echoes (DENSE) MRI can quantify regional stretch differences experienced by the vessel wall, and, in tandem with 3D volumetric MRI anatomic data and computational modeling can be used to calculate patient-specific mechanical wall stress. The aim of our study is to uncover important inflammatory changes and adverse hemodynamics and biomechanics that are not addressed by current imaging, and use them to predict AAA disease progression. We also seek to optimize a short (5 minute) MRI protocol without contrast to determine if there is added value to this comprehensive assessment, as fast non-contrast MRI would be preferable and more efficiently use VA resources. Our overall goal is to meaningfully advance the assessment of risk in veterans who do not meet current intervention thresholds and thereby in the future improve outcomes by refining surveillance imaging regimens and decisions regarding early intervention for AAAs.