Abdominal Aortic Aneurysm Stress Calculation with Calcification Correction
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Solution Overview
Problem
Current methods for determining stress in anatomical structures, such as the abdominal aorta, are inaccurate due to the lack of patient-specific wall material properties and thickness, and fail to accurately model calcifications, leading to inadequate rupture risk assessment in abdominal aortic aneurysms.
Innovation Solution
A method and apparatus that calculate first stress values based on a range of stiffness and correct second stress values to account for regions with different stiffness, using finite-element modeling and volume meshes to account for calcifications, enabling patient-specific and more accurate stress calculations in anatomical structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If patient-specific wall material properties and thickness are incorporated into stress calculations, then measurement precision of stress is improved, but device complexity and computational time increase
Solution Approach 1:
The vessel wall is segmented into multiple regions based on stiffness characteristics. Different regions (e.g., calcified vs. non-calcified areas) are assigned different material properties. This segmentation allows patient-specific stress calculations without requiring complete geometric modeling of every detail, thus improving precision while controlling complexity.
Solution Approach 2:
Different regions of the vessel wall are assigned different material properties based on their local characteristics. Calcified regions are modeled with higher stiffness than non-calcified regions. This local differentiation captures patient-specific variations in wall properties, improving stress measurement precision without requiring uniform complex modeling throughout the entire structure.
2Measurement precision
If calcifications are accurately geometrically modeled, then measurement precision of stress is improved, but computational time and model complexity increase
Solution Approach 1:
The calcification regions are extracted as separate entities from the overall vessel wall model. Instead of modeling every detail of calcifications within the full geometry, the method identifies calcified regions and applies corrected stress values specifically at these locations. This extraction approach improves precision for critical areas while reducing overall computational time.
Solution Approach 2:
Instead of fully modeling all calcification geometries in detail, the method applies partial correction factors to stress calculations at calcified regions. This partial action approach captures the essential mechanical effect of calcifications on stress distribution without requiring complete geometric representation, thus improving precision while significantly reducing computational time.
3Device complexity
If constant thickness and material properties are assumed for the AAA wall, then device complexity is reduced, but measurement precision of stress deteriorates
Solution Approach 1:
The method transitions from assuming uniform wall properties to assigning different material properties to different regions. By identifying calcified versus non-calcified regions and assigning appropriate stiffness values to each, the model captures patient-specific variations in wall properties, thereby improving stress measurement precision while maintaining relatively simple modeling assumptions.
Data Source
AI summary
A method of determining wall stress in an abdominal aortic aneurysm is disclosed. The method includes determining, from anatomical image data, respective first stress values at locations on the wall, based on the aorta having substantially uniform stiffness. The primary direction of stress those locations are determined, and the locations of calcified regions (20) are then determined. The distance to the nearest calcified region is then determined for each location not corresponding to a calcified region, and the additional stress caused by the calcified regions is then determined from values stored in a memory.