MRI of Structure and Function in Assessing Hemodynamic Impact on AAA Evolution

描述(由申请人提供)：腹主动脉瘤(AAA)是一种如果动脉瘤进展到破裂，可能会造成毁灭性后果的疾病。尽管AAA的进化是一个复杂的过程，可能是由生化和生物力学因素相互作用所调节的，而且尽管实体本身的几何和结构可变， 目前的临床标准取决于单个参数--最大管腔直径。根据临床指南，有大量的人的动脉瘤尚未达到大小(5.5厘米)，手术干预(开放手术或血管内支架植入)的益处超过了手术的风险。然后，这些患者将被警惕地等待。这个项目的假设是，血流动力学因素在决定给定的动脉瘤是否会比仅基于最大管腔直径估计的情况下进展得更快方面发挥着重要作用。该项目将开发先进的磁共振成像能力，以测量血管管腔和可能存在的任何腔内血栓的几何形态。还将实施血管顺应性和湍动能等功能特征的成像。同样，将执行高级计算流体动力学(CFD)模拟，以根据患者的具体情况模拟这些动脉瘤中的速度场。模拟将包括流体-结构相互作用、非层流效应和非牛顿项。这些方法的一致性将在相互交叉比较中进行检查，并与实验流动模型进行比较。将招募一组动脉瘤范围在3.5到5.0厘米之间的患者进行两年一次的成像。间隔数据集将彼此共同注册，并将测量动脉瘤形态的变化。然后，这些变化将与为该特定动脉瘤计算的血流动力学描述符相关联。我们会特别小心，以确保 项目的制定是为了在社区实践中提供与临床医生直接相关的数据报告和指导。这一提议的假设是，墙变小的区域 切应力与动脉瘤生长较快的区域相关。如果确实证明了这一点，该项目将提供工具来识别哪些患者，尽管动脉瘤相对较小，但可能进展迅速，反之，如果动脉瘤较大，患者的病情可能相对稳定。这些信息对于确保进展迅速的患者在进展到破裂之前得到治疗，以及稳定的动脉瘤患者可以免于过早手术将是重要的。

DESCRIPTION (provided by applicant): Abdominal Aortic Aneurysm (AAA) is a condition with potentially devastating outcomes if the aneurysm progresses to rupture. Although the evolution of AAA is a complex process that is likely mediated by an interplay of biochemical and biomechanical factors, and despite the geometrical and structural variability of the entity itself, current clinical criteria hinge on a single parameter - the maximal lumenal diameter. Under clinical guidelines, there is a large population of individuals who harbor aneurysms that have not yet reached a size (5.5 cms) where the benefit from surgical intervention (either open surgery or endovascular stent-graft placement) exceeds the risk of the procedure. These patients are then followed with watchful waiting. It is the hypothesis of this project that hemodynamic factors play an important role in determining whether a given aneurysm will progress more rapidly than would be estimated on the basis of maximal lumenal diameter alone. The project will develop advanced MRI capabilities to measure the geometric morphology of the vascular lumen and of any intralumenal thrombus that might be present. Imaging of functional characteristics such as vascular compliance and turbulent kinetic energy will also be implemented. Similarly, advanced Computational Fluid Dynamics (CFD) simulations will be performed to simulate, on a patient-specific basis, the velocity fields in these aneurysms. The simulations will include fluid-structur interactions, non-laminar effects, and non- Newtonian terms. Consistency of these methods will be checked in cross-comparison with one another, and against experimental flow models. A cohort of patients with aneurysms in the range from 3.5 to 5.0 cms will be recruited for bi-annual imaging. Interval data sets will be co-registered with each other and changes in aneurysm morphology will be measured. These changes will then be correlated with hemodynamic descriptors calculated for that specific aneurysm. Particular care will be taken to ensure that the project is formulated to provide data reporting and guidance that is directly relevant to the clinician in community practice. It is the hypothesis of this proposal that regions of reduced wall shear stress will correlate with regions of more rapid aneurysm growth. If this is indeed demonstrated to be the case, this project will provide the tools to identify patients who, despite relatively small aneurysm size, might be rapid progressors, and conversely, cases where patients with larger aneurysms might have relatively stable conditions. That information would be important in ensuring that rapid progressors are treated before they progress to rupture, and that patients with stable aneurysms can be spared premature surgeries.