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Micromechanical Characterization of Intra-luminal Thrombus Tissue from Abdominal Aortic Aneurysms
KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Biomechanics.
KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Biomechanics.
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2010 (English)In: Annals of Biomedical Engineering, ISSN 0090-6964, E-ISSN 1573-9686, Vol. 38, no 2, 371-379 p.Article in journal (Refereed) Published
Abstract [en]

The reliable assessment of Abdominal Aortic Aneurysm rupture risk is critically important in reducing related mortality without unnecessarily increasing the rate of elective repair. Intra-luminal thrombus (ILT) has multiple biomechanical and biochemical impacts on the underlying aneurysm wall and thrombus failure might be linked to aneurysm rupture. Histological slices from 7 ILTs were analyzed using a sequence of automatic image processing and feature analyzing steps. Derived microstructural data was used to define Representative Volume Elements (RVE), which in turn allowed the estimation of microscopic material properties using the non-linear Finite Element Method. ILT tissue exhibited complex microstructural arrangement with larger pores in the abluminal layer than in the luminal layer. The microstructure was isotropic in the abluminal layer, whereas pores started to orient along the circumferential direction towards the luminal site. ILT's macroscopic (reversible) deformability was supported by large pores in the microstructure and the inhomogeneous structure explains in part the radially changing macroscopic constitutive properties of ILT. Its microscopic properties decreased just slightly from the luminal to the abluminal layer. The present study provided novel microstructural and micromechanical data of ILT tissue, which is critically important to further explore the role of the ILT in aneurysm rupture. Data provided in this study allow an integration of structural information from medical imaging for example, to estimate ILT's macroscopic mechanical properties.

Place, publisher, year, edition, pages
2010. Vol. 38, no 2, 371-379 p.
Keyword [en]
Intra-luminal thrombus, Abdominal Aortic Aneurysm (AAA), Finite element, method (FEM), Microscale, Constitutive modeling, wall stress, rupture
National Category
Medical Laboratory and Measurements Technologies
Identifiers
URN: urn:nbn:se:kth:diva-19175DOI: 10.1007/s10439-009-9837-4ISI: 000274237000013Scopus ID: 2-s2.0-77249089737OAI: oai:DiVA.org:kth-19175DiVA: diva2:337222
Funder
Swedish Research Council, 2006-7568
Note
QC 20110124Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Multiscale Modeling of the Normal and Aneurysmatic Abdominal Aorta
Open this publication in new window or tab >>Multiscale Modeling of the Normal and Aneurysmatic Abdominal Aorta
2010 (English)Licentiate thesis, comprehensive summary (Other academic)
Place, publisher, year, edition, pages
Stockholm: KTH, 2010. 20 p.
Series
Trita-HFL. Report / Royal Institute of Technology, Solid Mechanics, ISSN 1654-1472 ; 0498
Identifiers
urn:nbn:se:kth:diva-28925 (URN)
Presentation
2010-12-20, Sal D3, Lindstedtsvägen 5, KTH, Stockholm, 10:15 (English)
Opponent
Supervisors
Note

QC 20110127

Available from: 2011-01-27 Created: 2011-01-24 Last updated: 2013-01-15Bibliographically approved
2. Biomechanics of abdominal aortic aneurysm:Experimental evidence and multiscale constitutive modeling
Open this publication in new window or tab >>Biomechanics of abdominal aortic aneurysm:Experimental evidence and multiscale constitutive modeling
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The reliable assessment of Abdominal Aortic Aneurysm (AAA) rupture risk is critically important in reducing related mortality without unnecessarily increasing the rate of elective repair. A multi-disciplinary approach including vascular biomechanics and constitutive modeling is needed to better understand and more effectively treat these diseases. AAAs are formed through irreversible pathological remodeling of the vascular wall and integrating this biological process in the constitutive description could improve the current understanding of this disease as well as the predictability of biomechanical simulations.

First in this thesis, multiple centerline-based diameter measurements between renal arteries and aortic bifurcation have been used to monitor aneurysm growth of in total 51 patients from Computer Tomography-Angiography (CT-A) data. Secondly, the thesis proposes a novel multi-scale constitutive model for the vascular wall, where collagen fibers are assembled by proteoglycan cross-linked collagen fibrils and reinforce an otherwise isotropic matrix (elastin). Collagen fibrils are dynamically formed by a continuous stretch-mediated process, deposited in the current configuration and removed by a constant degradation rate. The micro-plane concept is then used for the Finite Element (FE) implementation of the constitutive model. Finally, histological slices from intra-luminal thrombus (ILT) tissue were analyzed using a sequence of automatic image processing steps. Derived microstructural data were used to define Representative Volume Elements (RVEs), which in turn allowed the estimation of microscopic material properties using the non-linear FE.

The thesis showed that localized spots of fast diameter growth can be detected through multiple centerline-based diameter measurements all over the AAA sac. Consequently, this information might further reinforce the quality of aneurysm surveillance programs. The novel constitutive model proposed in the thesis has a strong biological motivation and provides an interface with biochemistry. Apart from modeling the tissue’s passive response, the presented model is helpful to predict saline feature of aneurysm growth and remodeling. Finally, the thesis provided novel microstructural and micromechanical data of ILT tissue, which is critically important to further explore the role of the ILT in aneurysm rupture.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. 48 p.
Series
Trita-HFL. Report / Royal Institute of Technology, Solid mechanics, ISSN 1654-1472 ; 0530
National Category
Mechanical Engineering Medical Engineering Materials Engineering Applied Mechanics
Identifiers
urn:nbn:se:kth:diva-101990 (URN)
Public defence
2012-09-20, Sal L1, Drottning Kristinas väg 30, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20120907

Available from: 2012-09-07 Created: 2012-09-06 Last updated: 2013-01-14Bibliographically approved

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