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Research Papers

Effects of Intraluminal Thrombus on Patient-Specific Abdominal Aortic Aneurysm Hemodynamics via Stereoscopic Particle Image Velocity and Computational Fluid Dynamics Modeling

[+] Author and Article Information
Chia-Yuan Chen

Department of Mechanical Engineering,
National Cheng Kung University,
Tainan 70101, Taiwan

Raúl Antón

Mechanical Engineering Department,
Tecnun-University of Navarra,
Navarra 20018, Spain

Ming-yang Hung, Prahlad Menon

Department of Biomedical Engineering,
Carnegie Mellon University,
Pittsburgh, PA 15219

Ender A. Finol

Department of Biomedical Engineering,
The University of Texas at San Antonio,
San Antonio, TX 78249

Kerem Pekkan

Department of Biomedical Engineering,
Carnegie Mellon University,
Pittsburgh, PA 15219
e-mail: kpekkan@andrew.cmu.edu

1Corresponding author.

Contributed by the Bioengineering Division of ASME for publication in the Journal OF Biomechanical Engineering. Manuscript received December 8, 2012; final manuscript received November 30, 2013; accepted manuscript posted December 5, 2013; published online February 13, 2014. Assoc. Editor: Naomi Chesler.

J Biomech Eng 136(3), 031001 (Feb 13, 2014) (9 pages) Paper No: BIO-12-1603; doi: 10.1115/1.4026160 History: Received December 08, 2012; Revised November 30, 2013; Accepted December 05, 2013

The pathology of the human abdominal aortic aneurysm (AAA) and its relationship to the later complication of intraluminal thrombus (ILT) formation remains unclear. The hemodynamics in the diseased abdominal aorta are hypothesized to be a key contributor to the formation and growth of ILT. The objective of this investigation is to establish a reliable 3D flow visualization method with corresponding validation tests with high confidence in order to provide insight into the basic hemodynamic features for a better understanding of hemodynamics in AAA pathology and seek potential treatment for AAA diseases. A stereoscopic particle image velocity (PIV) experiment was conducted using transparent patient-specific experimental AAA models (with and without ILT) at three axial planes. Results show that before ILT formation, a 3D vortex was generated in the AAA phantom. This geometry-related vortex was not observed after the formation of ILT, indicating its possible role in the subsequent appearance of ILT in this patient. It may indicate that a longer residence time of recirculated blood flow in the aortic lumen due to this vortex caused sufficient shear-induced platelet activation to develop ILT and maintain uniform flow conditions. Additionally, two computational fluid dynamics (CFD) modeling codes (Fluent and an in-house cardiovascular CFD code) were compared with the two-dimensional, three-component velocity stereoscopic PIV data. Results showed that correlation coefficients of the out-of-plane velocity data between PIV and both CFD methods are greater than 0.85, demonstrating good quantitative agreement. The stereoscopic PIV study can be utilized as test case templates for ongoing efforts in cardiovascular CFD solver development. Likewise, it is envisaged that the patient-specific data may provide a benchmark for further studying hemodynamics of actual AAA, ILT, and their convolution effects under physiological conditions for clinical applications.

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References

Figures

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Fig. 1

Transparent patient-specific rapid prototype replica, representative measurement planes, and corresponding anatomical views showing the geometry of each lumen. (a) AAA model without ILT and (b) AAA model with ILT. Left column: Transparent models; middle and right column: CFD models. Positions of three stereoscopic PIV measurement planes are outlined in red (top plane), green (middle plane), and blue (bottom plane).

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Fig. 2

Schematic representation of stereoscopic PIV configuration [45]

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Fig. 3

Before and after image preprocessing of stereoscopic PIV data from AAA model without ILT (left column: before; right column: after image preprocessing). Time between frame 1 and frame 2 was set to be 1.5 ms.

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Fig. 4

Stereoscopic PIV velocity data of both AAA models (a) without and (b) with ILT. Velocity fields on each measurement plane are shown in x (the first row), y (the second row), and z (the third row) directions. Unit of color bars: m/s.

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Fig. 5

Comparison of flow patterns between AAA models with and without ILT. A vortex was observed in the middle plane near the aneurysm bulge region of the AAA model without ILT as evidenced by (a) Vz contour map overlaid with 2D streamtraces at three measurement planes and (c) 2D velocity vectors overlapped with raw PIV image. No vortex was found in the same region of the AAA model with ILT as evidenced by (b) and (d).

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Fig. 6

Wall shear stress distribution for both AAA models. Unit of the color bar: Pa.

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Fig. 7

(a) Out-of-plane velocity data comparison of patient-specific AAA model without ILT using stereoscopic PIV, Fluent, and in-house CFD methods. Left panel: Out-of-plane velocity contour maps; right panel: quantitative velocity profile comparison. Data were extracted from each A-B line (50 mm) of contour plots (left panel). Correlation coefficients between stereoscopic PIV and Fluent, stereoscopic PIV and in-house CFD, and Fluent and in-house CFD are 0.92, 0.85, and 0.96, respectively. Unit of the color bar: m/s.

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