THE ROLE OF WALL STRESS DISTRIBUTION IN ABDOMINAL AORTIC

腹主动脉壁应力分布的作用

• 批准号: 6052065
• 负责人: MARK F FILLINGER
• 金额: $ 38.28万
• 依托单位: DARTMOUTH COLLEGE
• 依托单位国家: 美国
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-09-30 至 2002-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6052065
• 关键词: abdomen; aorta aneurysm; bioimaging /biomedical imaging; biomechanics; clinical research; computed axial tomography; computer simulation; diagnosis design /evaluation; disease /disorder proneness /risk; hemodynamics; human data; mechanical stress; muscle stress; physical model; prognosis; vascular smooth muscle

In the clinical management of patients with an abdominal aortic aneurysm (AAA), physicians have long sought the ability to reliably identify patients with a high risk of rupture and those who are relatively safe from rupture. More precise information regarding rupture risk would allow early corrective surgery for some and avoid unnecessary surgery for others. The proposed project deals with a biomechanical approach to predicting rupture, using the fundamental mechanical principles used by engineers to assess the safety of a pressure vessel. The basic premise is that rupture occurs when the mechanical stress (i.e., internal forces per unit area) on the AAA wall exceeds the maximum stress that the aneurysmal tissue can inherently withstand (i.e., failure strength). Thus, if the wall stresses on a particular AAA is known, then one may make a reliable prediction regarding its rupture risk. Currently, the rupture risk is known to be related to AAA diameter and the patient's blood pressure, and both of these factors are important determinants of aneurysm wall stress. Additionally however, stress is also greatly dependent on aneurysm shape, which is seldom considered in a clinical setting. This is in part because the technology needed to precisely determine the AAA shape (and thus the wall stress) did not exist until recently. With new Computed Tomography (CT) imaging, computer-generated three dimensional reconstructions of CT data and mathematical techniques, AAA wall stress can now be calculated using a computer model. The proposed project will consist of three major elements. One element will test the basic hypothesis that wall stress is directly related to AAA rupture. Stress analysis will be performed on 20 AAAs near the time of rupture (in cases where CT data was coincidentally obtained within 1 month of rupture) and on 50 size-matched AAAs that did not rupture in a longer time span. Three-dimensional wall stress distribution (including peak, mean, and cyclic wall stresses) will be compared in the two groups. Another major element of the study will involve the analysis of wall stress distribution in at least 30 AAAs that have been followed with CT scans over extended periods (because they did not have indications for surgery). Wall stress distribution will be evaluated over time to examine the role of biomechanics in AAA expansion and progression. This analysis will include the role of three-dimensional shape and how it changes over time. The third element of the project will involve refinement of the noninvasive methodology used to determine AAA wall stress distribution. The CT data from the other two elements of the study will be re-analyzed to determine the utility of proposed refinements in computer modeling of human AAAs. The proposed project will likely be the first study to perform stress analyses on human AAA during progression and near the time of rupture. The study can be performed without harming patient care because it uses data that has already been obtained during normal clinical care (similar to existing clinical studies of AAA diameter). The results from this study will provide critical insight into the role of wall stresses during AAA disease progression and rupture, and may give clinicians a noninvasive tool to more

在腹部主动脉瘤（AAA）患者的临床治疗中，医生长期以来一直在寻求可靠地识别出高爆发风险的患者，并且那些相对较不受破坏的患者。 有关破裂风险的更精确的信息将允许某些人的早期纠正手术，并避免对其他人进行不必要的手术。 拟议的项目介绍了一种生物力学方法来预测破裂，使用工程师用来评估压力容器安全的基本机械原理。 基本的前提是，当AAA壁上的机械应力（即每单位区域内部力量）超过动脉瘤组织可以固有地承受的最大应力（即失败强度）时，就会发生破裂。 因此，如果已知墙壁对特定AAA的压力，则可能会对其破裂风险做出可靠的预测。 目前，已知破裂风险与AAA直径和患者的血压有关，这两个因素都是动脉瘤壁应力的重要决定因素。 但是，应力也很大程度上取决于动脉瘤形状，在临床环境中很少考虑。 这部分是因为要精确确定AAA形状（以及因此壁应力）所需的技术直到最近才存在。 通过新的计算机断层扫描（CT）成像，计算机生成的CT数据和数学技术的三维重建现在可以使用计算机模型来计算AAA壁应力。拟议的项目将由三个主要要素组成。 一个元素将检验壁应力与AAA破裂直接相关的基本假设。 应力分析将在破裂时间附近的20个AAA上进行（如果在破裂后1个月内同时获得CT数据），并且在较长时间内没有破裂的50个尺寸匹配的AAA。 在两组中，将比较三维壁应力分布（包括峰值，平均值和环状壁应力）。 该研究的另一个主要要素将涉及至少30个AAA中壁应力分布的分析，这些AAA在长时间内进行了CT扫描（因为它们没有手术指示）。 随着时间的流逝，将评估壁应力分布，以检查生物力学在AAA扩张和进展中的作用。 该分析将包括三维形状的作用以及它随时间变化的变化。 该项目的第三个要素将涉及用于确定AAA壁应力分布的非侵入性方法。 研究的其他两个要素的CT数据将被重新分析，以确定人类AAAS计算机建模中提出的改进的实用性。拟议的项目可能是第一个在进展过程中对人AAA进行压力分析的第一项研究，并接近破裂时期。 该研究可以在不损害患者护理的情况下进行，因为它使用了正常临床护理期间已经获得的数据（类似于现有的AAA直径临床研究）。 这项研究的结果将为壁应力在AAA疾病进展和破裂过程中的作用提供批判性的见解，并可能使临床医生成为一种无创的工具