A search in Scopus within "Article title, Abstract, Keywords" unveils 2,444 documents focused on the biomechanics of Abdominal Aortic Aneurysm (AAA), mostly on AAA wall stress. Only 24 documents investigated AAA kinematics, an important topic that could potentially offer significant insights into the biomechanics of AAA. In this paper, we present an image-based approach for patient-specific, in vivo, and non-invasive AAA kinematic analysis using patient's time-resolved 3D computed tomography angiography (4D-CTA) images, with an objective to measure wall displacement and strain during the cardiac cycle. Our approach relies on regularized deformable image registration for estimating wall displacement, estimation of the local wall strain as the ratio of its normal displacement to its local radius of curvature, and local surface fitting with non-deterministic outlier detection for estimating the wall radius of curvature. We verified our approach against synthetic ground truth image data created by warping a 3D-CTA image of AAA using a realistic displacement field obtained from a finite element biomechanical model. We applied our approach to assess AAA wall displacements and strains in ten patients. Our kinematic analysis results indicated that the 99th percentile of circumferential wall strain, among all patients, ranged from 2.62% to 5.54%, with an average of 4.45% and a standard deviation of 0.87%. We also observed that AAA wall strains are significantly lower than those of a healthy aorta. Our work demonstrates that the registration-based measurement of AAA wall displacements in the direction normal to the wall is sufficiently accurate to reliably estimate strain from these displacements.

翻译：在Scopus数据库中以"文章标题、摘要、关键词"为范围进行检索，共发现2,444篇专注于腹主动脉瘤（AAA）生物力学的文献，其中大部分集中于AAA壁应力研究。仅有24篇文献探讨了AAA运动学这一重要课题，该领域可能为AAA生物力学提供关键性见解。本文提出一种基于医学影像的患者特异性、在体、无创AAA运动学分析方法，利用患者的时间分辨三维计算机断层扫描血管造影（4D-CTA）图像，旨在测量心动周期中血管壁的位移与应变。该方法通过正则化可变形图像配准估算血管壁位移，以法向位移与局部曲率半径之比计算局部壁面应变，并采用带非确定性异常值检测的局部曲面拟合技术估算血管壁曲率半径。我们通过有限元生物力学模型生成真实位移场，对AAA三维CTA图像进行形变处理创建合成基准图像数据，从而验证了本方法的有效性。我们将该方法应用于十例患者的AAA壁位移与应变评估。运动学分析结果显示：所有患者AAA壁周向应变的第99百分位数介于2.62%至5.54%之间，平均值为4.45%，标准差为0.87%。同时观察到AAA壁应变显著低于健康主动脉壁应变。本研究证明，基于图像配准的AAA壁法向位移测量具有足够精度，能够从这些位移中可靠地推算出应变值。