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Research Papers

In Vitro Validation of Finite-Element Model of AAA Hemodynamics Incorporating Realistic Outlet Boundary Conditions

[+] Author and Article Information
Ethan O. Kung, Andrea S. Les

Department of Bioengineering, Stanford University, Stanford, CA 94305

Francisco Medina, Ryan B. Wicker

W.M. Keck Center for 3D Innovation, University of Texas at El Paso, El Paso, TX 79968

Michael V. McConnell

Department of Medicine, Stanford University, Stanford, CA 94305

Charles A. Taylor1

Department of Bioengineering, and Department of Surgery, Stanford University, Stanford, CA 94305taylorca@stanford.edu

1

Corresponding author.

J Biomech Eng 133(4), 041003 (Feb 23, 2011) (11 pages) doi:10.1115/1.4003526 History: Received September 28, 2010; Revised January 12, 2011; Posted January 28, 2011; Published February 23, 2011; Online February 23, 2011

The purpose of this study is to validate numerical simulations of flow and pressure in an abdominal aortic aneurysm (AAA) using phase-contrast magnetic resonance imaging (PCMRI) and an in vitro phantom under physiological flow and pressure conditions. We constructed a two-outlet physical flow phantom based on patient imaging data of an AAA and developed a physical Windkessel model to use as outlet boundary conditions. We then acquired PCMRI data in the phantom while it operated under conditions mimicking a resting and a light exercise physiological state. Next, we performed in silico numerical simulations and compared experimentally measured velocities, flows, and pressures in the in vitro phantom to those computed in the in silico simulations. There was a high degree of agreement in all of the pressure and flow waveform shapes and magnitudes between the experimental measurements and simulated results. The average pressures and flow split difference between experiment and simulation were all within 2%. Velocity patterns showed good agreement between experimental measurements and simulated results, especially in the case of whole-cycle averaged comparisons. We demonstrated methods to perform in vitro phantom experiments with physiological flows and pressures, showing good agreement between numerically simulated and experimentally measured velocity fields and pressure waveforms in a complex patient-specific AAA geometry.

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Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 1

Anatomical phantom model. (a) MR imaging data from an AAA patient. (b) 3D computer model constructed based on patient imaging data. (c) Physical phantom constructed from 3D computer model.

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Figure 2

In vitro experiment flow system setup diagram

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Figure 3

(a) The physical Windkessel module assembly and the corresponding analytical representation. (b) The resistance module. (c) The capacitance module.

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Figure 4

PCMRI measured flow through the abdominal aorta at different slice locations (S1–S3) for (a) resting condition and (b) light exercise condition

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Figure 5

PCMRI versus ultrasonic flow probe measured total inlet flow for (a) resting condition and (b) light exercise condition

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Figure 6

Measured in vitro (solid lines) versus simulated in silico (dashed lines) pressure and flow waveforms for (a) resting condition and (b) light exercise condition

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Figure 7

Resting condition flow velocity comparisons: between MR measurements and FEA results at the (a) diastole, (b) acceleration, (c) systole, and (d) deceleration time point at three different slice locations (S1–S3). Color map and arrows correspond to through-plane and in-plane velocities, respectively.

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Figure 8

Light exercise flow velocity comparisons: between MR measurements and FEA results at the (a) diastole, (b) acceleration, (c) systole, and (d) deceleration time point at three different slice locations (S1–S3). Color map and arrows correspond to through-plane and in-plane velocities, respectively.

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Figure 9

Whole-cycle averaged flow velocity comparisons: between MR measurements and FEA results at three different slice locations (S1–S3) for (a) resting condition and (b) light exercise condition

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