Bioengineering Studies of Abdominal Aortic Aneurysm Fluid and Wall Dynamics

描述(由申请人提供)：这项建议旨在调查一个中心假设，即一旦诊断出动脉瘤，在动态评估动脉瘤力学的背景下，破裂可能性的主要生物力学决定因素是不均匀的动脉壁厚度。我们的总体目标是通过预测将接受选择性修复的受试者的特定患者的AAA破裂风险并回顾检查破裂的动脉瘤来解决这一假设。通过对腹主动脉血流、瘤壁厚度和室壁运动的无创性评估，可以重现天然腹主动脉的生物力学环境，因为它是由心动周期调节的。需要评估的AAA破裂风险的动态指标包括峰值壁应力、峰值动脉瘤囊内压力以及动脉瘤壁厚的空间和时间变化。回顾评估破裂动脉瘤的这些指标将提供一个临界值，未来诊断的AAA可以用来评估其在临床环境中发生机械故障的可能性。这些生物力学和临床终点将使用标准的计算和成像技术(流体-结构相互作用建模、电影、相位对比和自旋回波磁共振成像、计算机断层成像、分割和重建算法、粒子图像测速仪和软组织力学框架)进行评估。此外，(I)我们提出了一种新的基于软组织应变能函数的AAA管壁力学性能的本构材料模型，该模型解释了胶原纤维网络的各向异性和排列；(Ii)我们开发了一种新的方法，基于从医学图像重建的加压几何形状来计算腹主动脉的零压配置；以及(Iii)我们开发了一个定制的代码，用于根据活体相位对比MRI数据计算阻抗派生的流出边界条件。这项建议代表了一项初步研究，旨在开发一种方法学，在评估AAA破裂潜力的背景下，动态评估AAA的生物力学。预测患病腹主动脉所需承受的体内力量将使AAA患者的手术治疗能够及时且具有成本效益地进行规划，并量身定做，以防止这种动态导致的灾难性事件，在改善患者生活质量的同时提供更好的护理。拟议研究的创新性质不仅基于非侵入性方法学，还基于本文所使用的数值技术的史无前例的验证，以及在患者检查时测量的患者特定的腔内血流条件和动脉壁厚度的应用。 公共卫生相关性：该奖项将有助于开发一种方法，非侵入性地估计腹主动脉瘤(AAA)的壁厚并评估其破裂可能性。我们将结合临床成像和计算方法来重建特定患者的动脉瘤，并通过计算机预测和验证施加在动脉上的力来评估破裂的风险。这一方法有望极大地提高血管手术和血管内治疗在未来心血管疾病管理中的术前规划能力。

DESCRIPTION (provided by applicant): This proposal is designed to investigate the central hypothesis that, once an aneurysm is diagnosed, the primary biomechanical determinant of rupture potential is the non-uniform arterial wall thickness, within the context of a dynamic assessment of aneurysm mechanics. Our overall goal is to address this hypothesis by predicting AAA risk of rupture on a patient-specific basis for subjects that will undergo elective repair and retrospectively examining ruptured aneurysms. The biomechanical environment of the native AAAs will be reproduced by non-invasively evaluating blood flow in the abdominal aorta, aneurysmal wall thickness and wall motion as it is mediated by the cardiac cycle. Dynamic indicators of AAA risk of rupture to be evaluated include peak wall stress, peak intra-aneurysmal sac pressure, and spatial and temporal changes in aneurysmal wall thickness. Retrospectively evaluating these indicators for ruptured aneurysms will provide a threshold for which future diagnosed AAAs can be measured against to assess their potential for mechanical failure in a clinical setting. These biomechanical and clinical endpoints will be assessed using standard computational and imaging techniques (fluid-structure interaction modeling, cine, phase-contrast and spin echo magnetic resonance imaging, computed tomography imaging, segmentation and reconstruction algorithms, particle image velocimetry, and soft tissue mechanics frameworks). In addition, (i) we propose a novel constitutive material model for the mechanical properties of the AAA wall based on a strain energy function for soft tissues that accounts for anisotropy and arrangement of a collagen fiber network; (ii) we have developed a new method for calculating the zero-pressure configuration of the abdominal aorta based on the pressurized geometry reconstructed from medical images; and (iii) we have developed a custom-based code for calculation of impedance-derived outflow boundary conditions from in vivo phase-contrast MRI data. This proposal represents a pilot study for the development of a methodology to specifically evaluate the biomechanics of AAAs dynamically within the context of assessing their rupture potential. Predicting the in vivo forces the diseased abdominal aorta is required to withstand will allow surgical management of AAA patients to be planned in a timely and cost-effective manner and tailored to prevent catastrophic events resulting from this dynamics, providing better care while improving the quality of life of the patients. The innovative nature of the proposed research is based not only on the non-invasive methodology, but also on the unprecedented validation of the numerical techniques used herein, and the application of patient-specific intraluminal flow conditions and arterial wall thickness measured at the time of patient examination. PUBLICE HEALTH RELEVANCE: This award will enable the development of a methodology for non-invasively estimating wall thickness in abdominal aortic aneurysms (AAAs) and assessing their rupture potential. We will combine clinical imaging with computational methods to reconstruct patient-specific aneurysms and evaluate the risk of rupture by means of computer prediction and validation of the forces exerted on the artery. This methodology is expected to greatly enhance the presurgical planning capabilities of vascular surgeries and endovascular therapies in the future management of cardiovascular diseases.