  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 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. 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 3.16% to 7.31%, with an average of 5.36% and a standard
deviation of 1.28%.
