2019 Cebull JBME.pdf

Current in vivo abdominal aortic aneurysm (AAA) imaging approaches tend to focus on

maximum diameter but do not measure three-dimensional (3D) vascular deformation or

strain. Complex vessel geometries, heterogeneous wall compositions, and surrounding

structures can all influence aortic strain. Improved understanding of complex aortic kinematics

has the potential to increase our ability to predict aneurysm expansion and eventual

rupture. Here, we describe a method that combines four-dimensional (4D)

ultrasound and direct deformation estimation to compute in vivo 3D Green-Lagrange

strain in murine angiotensin II-induced suprarenal dissecting aortic aneurysms, a commonly

used small animal model. We compared heterogeneous patterns of the maximum,

first-component 3D Green-Lagrange strain with vessel composition from mice with varying

AAA morphologies. Intramural thrombus and focal breakage in the medial elastin

significantly reduced aortic strain. Interestingly, a dissection that was not detected with

high-frequency ultrasound also experienced reduced strain, suggesting medial elastin

breakage that was later confirmed via histology. These results suggest that in vivo measurements

of 3D strain can provide improved insight into aneurysm disease progression.

While further work is needed with both preclinical animal models and human imaging

studies, this initial murine study indicates that vessel strain should be considered when

developing an improved metric for predicting aneurysm growth and rupture.

[DOI: 10.1115/1.4043075]