Advanced MRI Evaluation of Abdominal Aortic Aneurysms

腹主动脉瘤(AAA)很常见，如果进展到破裂，可能会危及生命。他们 据报道，高达8%的老年男性患有这种疾病，每年有超过15,000人死亡。基本容器 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。但有一种方法 与其说是维度，不如说是故事本身。使用计算生物力学模型估计的壁应力可能 与直径相比，更好地预测生长和破裂。此外，AAA的增长往往不是持续的，而且 相反，它的特点是先是快速增长，然后是停滞。小系列报道无关外科手术 手术可导致腹主动脉破裂，提示间歇性和异质性炎症过程。 同时，不利的血流动力学和生物力学对AAA疾病的进展也很重要。 新的功能成像技术比功能成像技术更能充分揭示主动脉疾病的复杂性 仅进行传统的解剖分析。虽然AAA已经被广泛研究，但疾病的机制 进展还没有完全阐明。如果更好地理解，它们可能会导致显著改善 小AAA退伍军人的管理(&lt；5.5厘米)。这些动脉瘤中的许多都可以安全地追踪。 筛查间隔时间长达2-3年，但有些可进展为破裂。识别这个子集将 大大简化了患有AAA的退伍军人的监控成像。另一方面，大多数AAA 永不破裂，识别低风险退伍军人可以帮助更好地管理资源，并仅针对那些 真正面临干预风险的退伍军人。 MRI独一无二地提供了对作用于血管壁的力(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)。血液流动 使用时间分辨3D相位对比磁共振成像(4D Flow)可以对关键参数进行量化，包括 流动湍流和壁面剪应力。动态增强(DCE)MRI可提供有效的评估 主动脉壁发炎。电影置换编码与刺激回声(高密度)MRI可以量化 血管壁的局部拉伸差异，并结合3D容积MRI解剖学 数据和计算模型可用于计算患者特定的机械壁应力。 我们研究的目的是揭示重要的炎症变化和不利的血流动力学和 目前的成像没有解决的生物力学，并使用它们来预测AAA疾病的进展。 我们还试图优化一种短时间(5分钟)的磁共振成像方案，而不进行对比，以确定是否具有附加值 对于这种全面的评估，因为快速非对比MRI将是更可取的，并且更有效地使用VA 资源。我们的总体目标是有意义地推进对不符合条件的退伍军人的风险评估 目前的干预阈值，从而在未来通过改进监视成像来改善结果 有关AAA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.