Key result
Pressurized abdominal aortic aneurysm models underestimated peak wall stress by an average of 15% compared to unloaded models derived using the novel methodology.
Effect estimate: 15% underestimation in comparator
Generating unloaded AAA volume meshes prior to finite element analysis is important, as pressurized models underestimate peak wall stress by 15%, impacting rupture risk assessment.
May improve AAA biomechanical modeling from routine CT; leaves open prospective patient validation.
In this work, we present a novel method for the derivation of the unloaded geometry of an abdominal aortic aneurysm (AAA) from a pressurized geometry in turn obtained by 3D reconstruction of computed tomography (CT) images. The approach was experimentally validated with an aneurysm phantom loaded with gauge pressures of 80, 120, and 140 mm Hg. The unloaded phantom geometries estimated from these pressurized states were compared to the actual unloaded phantom geometry, resulting in mean nodal surface distances of up to 3.9% of the maximum aneurysm diameter. An in-silico verification was also performed using a patient-specific AAA mesh, resulting in maximum nodal surface distances of 8 μm after running the algorithm for eight iterations. The methodology was then applied to 12 patient-specific AAA for which their corresponding unloaded geometries were generated in 5-8 iterations. The wall mechanics resulting from finite element analysis of the pressurized (CT image-based) and unloaded geometries were compared to quantify the relative importance of using an unloaded geometry for AAA biomechanics. The pressurized AAA models underestimate peak wall stress (quantified by the first principal stress component) on average by 15% compared to the unloaded AAA models. The validation and application of the method, readily compatible with any finite element solver, underscores the importance of generating the unloaded AAA volume mesh prior to using wall stress as a biomechanical marker for rupture risk assessment.
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Chandra et al. (2016) studied Abdominal aortic aneurysm (n=12). Unloaded AAA geometry derivation method vs. Pressurized AAA models (CT image-based) was evaluated on Peak wall stress (first principal stress component) (15% underestimation in comparator). Pressurized abdominal aortic aneurysm models underestimated peak wall stress by an average of 15% compared to unloaded models derived using the novel methodology.
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