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An Objective and Repeatable Sac Isolation Technique for Comparing Biomechanical Metrics in Abdominal Aortic Aneurysms
Timothy K Chung1, Pete H Gueldner1, Trevor M Kickliter2
1Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15260, USA.
Bioengineering (Basel, Switzerland)
|November 10, 2022
Summary
Isolating the abdominal aortic aneurysm (AAA) sac improves biomechanical analysis. This novel sac-isolation technique reveals significant differences in wall stress between stable and unstable AAA, unlike traditional methods.
Area of Science:
- Biomedical Engineering
- Medical Imaging Analysis
- Computational Mechanics
Background:
- Current biomechanical analyses of abdominal aortic aneurysms (AAA) often include non-dilated regions, potentially leading to inaccurate stress estimations.
- Accurate assessment of AAA wall stress is crucial for predicting rupture risk and patient outcomes.
- Existing methods may not adequately differentiate between stable and unstable AAA based on biomechanical metrics.
Purpose of the Study:
- To develop and validate a novel algorithm for isolating the abdominal aortic aneurysm (AAA) sac in biomechanical analyses.
- To compare peak wall stress (PWS) and mean wall stress (MWS) using both the entire aneurysm and the isolated sac.
- To investigate if sac isolation can reveal significant differences in wall stress between stable and unstable AAA.
Main Methods:
- A cohort of 245 patient CT image sets was used, with aneurysms categorized as stable or unstable.
- A novel sac-isolation algorithm involving 3D surface rotation, 2D projection, Fourier series fitting, and local extrema identification was applied.
- Finite element analysis was performed to calculate PWS and MWS on the entire aneurysm and the isolated sac, followed by statistical comparison.
Main Results:
- Mean wall stress (MWS) differed significantly between the isolated sac and the entire aneurysm, whereas peak wall stress (PWS) did not.
- No significant differences in wall stress were found between stable and unstable AAA when analyzing the entire aneurysm.
- Using the isolated sac, both PWS and MWS were significantly higher in unstable AAA compared to stable AAA (p=0.003 and p=0.022, respectively).
Conclusions:
- Evaluating only the abdominal aortic aneurysm (AAA) sac region significantly influences wall stress metrics.
- The novel sac-isolation technique enhances the ability to detect biomechanical differences between stable and unstable AAA.
- This approach may improve the accuracy of AAA rupture risk assessment by focusing on the critical dilated sac region.
