Abdominal aortic aneurysm (AAA) is a life-threatening condition characterized by the progressive dilation of the aorta, which can lead to rupture if undetected or untreated. Stress-based rupture risk estimation using computational biomechanics has been widely studied; however, it requires wall strength data that cannot be measured in humans in vivo. To overcome this limitation, the goal of this study is to present a new method for biomechanical assessment of AAA via simultaneous consideration of tension and strain in AAA wall. We present a patient-specific, non-invasive method for assessing the structural integrity of the AAA wall using only time-resolved 3D computed tomography angiography (4D-CTA) images and blood pressure data. The proposed approach integrates wall strain (throughout the cardiac cycle) and wall tension analysis to compute a novel index, the Relative Structural Integrity Index (RSII), which quantifies local wall stiffness independently of wall thickness, wall material properties, and blood pressure measurement conditions. We applied our method to twenty patients from three different hospitals to extract visual RSII maps over the AAA wall of each individual patient and to compare the RSII values between aneurysmal and non-aneurysmal aortas in one patient. Our results primarily show similar RSII values across all patients, indicating the consistency of the method. Additionally, we observed patterns consistent with experimental findings reported in the literature: AAA walls exhibited higher stiffness than healthy aortic walls, while localized low-stiffness zones in the AAA wall were predominantly found in the most dilated regions.

翻译：腹主动脉瘤（AAA）是一种危及生命的疾病，其特征是主动脉进行性扩张，若未及时发现或治疗可能导致破裂。基于计算生物力学的应力破裂风险评估已被广泛研究；然而，该方法需要无法在人体内直接测量的血管壁强度数据。为克服这一局限，本研究旨在提出一种通过同时考虑AAA血管壁张力和应变的新型生物力学评估方法。我们提出了一种基于患者特异性、非侵入性的AAA血管壁结构完整性评估方法，仅使用时序分辨的三维计算机断层扫描血管造影（4D-CTA）图像和血压数据。该方法整合血管壁应变（贯穿整个心动周期）与血管壁张力分析，计算出一个新型指标——相对结构完整性指数（RSII），该指标可独立于血管壁厚度、血管壁材料特性和血压测量条件，量化局部血管壁刚度。我们将该方法应用于来自三家不同医院的二十名患者，提取每位患者AAA血管壁的可视化RSII图谱，并在一名患者中比较动脉瘤区域与非动脉瘤主动脉的RSII值。结果主要显示所有患者的RSII值具有相似性，表明该方法具有一致性。此外，我们观察到的模式与文献报道的实验结果相符：AAA血管壁表现出比健康主动脉壁更高的刚度，而AAA血管壁中的局部低刚度区域主要出现在扩张最显著的部位。