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Research Papers

Stereoscopically Observed Deformations of a Compliant Abdominal Aortic Aneurysm Model

[+] Author and Article Information
Clark A. Meyer, Eric Bertrand

 Equipe de Biomécanique, Institut de Recherche sur les Phénomènes Hors Equilibre (IRPHE) UMR 6594, Centre National de la Recherche Scientifique (CNRS), 13384 Marseille, France

Olivier Boiron1

 Equipe de Biomécanique, Institut de Recherche sur les Phénomènes Hors Equilibre (IRPHE) UMR 6594, Centre National de la Recherche Scientifique (CNRS), 13384 Marseille, France

Valérie Deplano2

 Equipe de Biomécanique, Institut de Recherche sur les Phénomènes Hors Equilibre (IRPHE) UMR 6594, Centre National de la Recherche Scientifique (CNRS), 13384 Marseille, Francedeplano@irphe.univ-mrs.fr

1

Also at Ecole Centrale, Marseille, France.

2

Address for correspondence: Valérie Deplano, Technopôle de Château Gombert, 49 rue F. Joliot Curie, B.P. 146, 13384 Marseille Cedex 13, France.

J Biomech Eng 133(11), 111004 (Nov 28, 2011) (8 pages) doi:10.1115/1.4005416 History: Received March 04, 2011; Revised October 25, 2011; Posted November 01, 2011; Published November 28, 2011; Online November 28, 2011

A new experimental setup has been implemented to precisely measure the deformations of an entire model abdominal aortic aneurysm (AAA). This setup addresses a gap between the computational and experimental models of AAA that have aimed at improving the limited understanding of aneurysm development and rupture. The experimental validation of the deformations from computational approaches has been limited by a lack of consideration of the large and varied deformations that AAAs undergo in response to physiologic flow and pressure. To address the issue of experimentally validating these calculated deformations, a stereoscopic imaging system utilizing two cameras was constructed to measure model aneurysm displacement in response to pressurization. The three model shapes, consisting of a healthy aorta, an AAA with bifurcation, and an AAA without bifurcation, were also evaluated with computational solid mechanical modeling using finite elements to assess the impact of differences between material properties and for comparison against the experimental inflations. The device demonstrated adequate accuracy (surface points were located to within 0.07 mm) for capturing local variation while allowing the full length of the aneurysm sac to be observed at once. The experimental model AAA demonstrated realistic aneurysm behavior by having cyclic strains consistent with reported clinical observations between pressures 80 and 120 mm Hg. These strains are 1–2%, and the local spatial variations in experimental strain were less than predicted by the computational models. The three different models demonstrated that the asymmetric bifurcation creates displacement differences but not cyclic strain differences within the aneurysm sac. The technique and device captured regional variations of strain that are unobservable with diameter measures alone. It also allowed the calculation of local strain and removed rigid body motion effects on the strain calculation. The results of the computations show that an asymmetric aortic bifurcation created displacement differences but not cyclic strain differences within the aneurysm sac.

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Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 1

Rendered views of aorta models (top to bottom): AAA without bifurcation, AAA with bifurcation, and healthy aorta with bifurcation

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Figure 2

Optical imaging setup with AB model and representative images from the device of the AU model with temporary point markings

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Figure 3

Positions of the surface at diastolic pressure are color coded with contour lines, showing shape variations between models with (a) anterior-posterior direction, (b) axial direction, and (c) lateral direction

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Figure 4

Cyclic displacements in the (a) anterior-posterior direction, (b) axial direction, and (c) lateral direction. These cyclic displacements are defined as the positions of nodes at 120 mm Hg minus their position at 80 mm Hg. They are plotted on position observed at 80 mm Hg.

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Figure 5

Strain patterns where strain is relative to diastolic positions

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