On the Quantification of Wall Stress in Patient Specific AAA Models




Vaughn, Reginald Jerome, Jr.

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An abdominal aortic aneurysm (AAA) is a cardiovascular condition located in the infrarenal segment of the aorta and characterized by an enlargement of the vessel. Rupture risk factors, such as wall stress, have been proposed to better identify those aneurysms that should be repaired. The primary goal of the research is to assess the importance of patient specific wall thickness on the ensuing wall stress when the finite element models are created with the unpressurized AAA geometry. Therefore, for each of the 12 AAA patients, four FEA models were created: (i) image-based (IB) AAA geometry with uniform thickness, (ii) IB AAA geometry with patient specific thickness, (iii) zero-pressure (ZP) AAA geometry with uniform thickness, and (iv) ZP AAA geometry with patient specific thickness. A series of tests of hypotheses was performed to determine if there were any statistically significant differences between the mean values of PWS, 99thWS, and SAWS amongst the aforementioned FEA model types. Mean 99thWS was 15% higher for the ZP geometries compared to their IB counterparts (43.1 N/cm2 vs. 37.4 N/cm2, p = 0.0004) for uniform wall thickness. Mean SAWS was 17% higher for the IB geometries with uniform wall thickness (19.7 N/cm2 vs. 16.9 N/cm2, p < 0.0001) and 20% higher for the ZP geometries with non-uniform wall thickness (18.3 N/cm2 vs. 15.3 N/cm2, p = 0.0011). When modeling AAA with patient specific, non-uniform wall thickness, the unstressed aneurysm geometry becomes relevant only if SAWS is the metric representative of the biomechanical state of the aneurysm.


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Abodominal, aneurysm, Aortic, cardiovascular, FEA



Biomedical Engineering