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Research Papers

A Methodology for Verifying Abdominal Aortic Aneurysm Wall Stress

[+] Author and Article Information
Sergio Ruiz de Galarreta

Department of Mechanical Engineering,
TECNUN,
University of Navarra,
Paseo Manuel de Lardizabal, 13,
San Sebastián 20018, Spain
e-mail: sruiz@tecnun.es

Aitor Cazón

Department of Mechanical Engineering,
TECNUN,
University of Navarra,
Paseo Manuel de Lardizabal, 13,
San Sebastián 20018, Spain
e-mail: acazon@tecnun.es

Raúl Antón

Department of Mechanical Engineering,
TECNUN,
University of Navarra,
Paseo Manuel de Lardizabal, 13,
San Sebastián 20018, Spain
e-mail: ranton@tecnun.es

Ender A. Finol

Department of Biomedical Engineering,
The University of Texas at San Antonio,
One UTSA Circle, AET 1.360,
San Antonio, TX 78249-0669
e-mail: ender.finol@utsa.edu

1Corresponding author.

Manuscript received June 10, 2016; final manuscript received September 6, 2016; published online November 4, 2016. Assoc. Editor: Keefe B. Manning.

J Biomech Eng 139(1), 011006 (Nov 04, 2016) (9 pages) Paper No: BIO-16-1245; doi: 10.1115/1.4034710 History: Received June 10, 2016; Revised September 06, 2016

An abdominal aortic aneurysm (AAA) is a permanent focal dilatation of the abdominal aorta of at least 1.5 times its normal diameter. Although the criterion of maximum diameter is still used in clinical practice to decide on a timely intervention, numerical studies have demonstrated the importance of other geometric factors. However, the major drawback of numerical studies is that they must be validated experimentally before clinical implementation. This work presents a new methodology to verify wall stress predicted from the numerical studies against the experimental testing. To this end, four AAA phantoms were manufactured using vacuum casting. The geometry of each phantom was subject to microcomputed tomography (μCT) scanning at zero and three other intraluminal pressures: 80, 100, and 120 mm Hg. A zero-pressure geometry algorithm was used to calculate the wall stress in the phantom, while the numerical wall stress was calculated with a finite-element analysis (FEA) solver based on the actual zero-pressure geometry subjected to 80, 100, and 120 mm Hg intraluminal pressure loading. Results demonstrate the moderate accuracy of this methodology with small relative differences in the average wall stress (1.14%). Additionally, the contribution of geometric factors to the wall stress distribution was statistically analyzed for the four phantoms. The results showed a significant correlation between wall thickness and mean curvature (MC) with wall stress.

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Figures

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Fig. 1

Conventional stress–strain diagrams for the 7160 and 7190 materials obtained with uniaxial tensile experiments with an inset illustrating the low strain region of the diagrams

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Fig. 2

Flow diagram of the numerical and experimental protocols followed in this work for the verification of AAA wall stress predicted by FEA

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Fig. 3

Numerical and experimental wall stress distributions for the 7160a and 7190a models

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Fig. 4

The 15 regions of wall stress concentration on the outer (left) and inner (right) wall used for the comparison study

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Fig. 5

Stress versus thickness, stress versus mean curvature, and stress versus Gaussian curvature scatter plots for the 7160a (outer) and 7190b (inner) models

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Fig. 6

Stress, mean curvature, and wall thickness distributions for the 7190a model. Regions #1 and #2 enclose seven representative zones ((a)–(g)) that explain the statistical results.

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Fig. 7

Wall stress distribution in the 7190b model for the three pressure loading conditions

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