The Role of Geometric and Biomechanical Factors in Abdominal Aortic Aneurysm Rupture Risk Assessment

Raut, Samarth S.; Chandra, Santanu; Shum, Judy; Finol, Ender A.

doi:10.1007/s10439-013-0786-6

Cited by 80 publications

(69 citation statements)

References 98 publications

(145 reference statements)

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“…There are several studies in the literature comparing FSI and noFSI analyses for single-layered aneurysm models [9,37,38]. Those studies suggested that applying transient pressure uniformly on the lumen sac for the noFSI analysis could be an adequate alternative to FSI analysis for the rupture risk criteria [2]. Khanafer et al [38], in his single-layered axisymmetric AAA model, stated that structural-only analysis, with uniformly applied time-dependent pressure inside the aneurysm lumen, underestimated peak wall stress (PWS) by 8% compared to the FSI analysis at the time of the peak wall stress.…”

Section: Aneurysm Modelmentioning

confidence: 99%

“…Cerebral artery aneurysms (CAA) and abdominal aortic aneurysms (AAA) are the most common aneurysm types. The AAA arises in the infrarenal aorta with a diameter greater than 3 cm and can be up to 9 cm in length [1,2]. Most of the studies on aneurysms have focused on already existing realistic or idealized aneurysms [33][34][35][36][37][38][39][40][41][42][43] with the aim of defining a relevant rupture criterion [4,7,10,19,20,24].…”

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confidence: 99%

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Investigation of material modeling in fluid–structure interaction analysis of an idealized three-layered abdominal aorta: aneurysm initiation and fully developed aneurysms

Şimşek

Kwon

2015

J Biol Phys

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Different material models for an idealized three-layered abdominal aorta are compared using computational techniques to study aneurysm initiation and fully developed aneurysms. The computational model includes fluid-structure interaction (FSI) between the blood vessel and the blood. In order to model aneurysm initiation, the medial region was degenerated to mimic the medial loss occurring in the inception of an aneurysm. Various cases are considered in order to understand their effects on the initiation of an abdominal aortic aneurysm. The layers of the blood vessel were modeled using either linear elastic materials or Mooney-Rivlin (otherwise known as hyperelastic) type materials. The degenerated medial region was also modeled in either linear elastic or hyperelastic-type materials and assumed to be in the shape of an arc with a thin width or a circular ring with different widths. The blood viscosity effect was also considered in the initiation mechanism. In addition, dynamic analysis of the blood vessel was performed without interaction with the blood flow by applying time-dependent pressure inside the lumen in a three-layered abdominal aorta. The stresses, strains, and displacements were compared for a healthy aorta, an initiated aneurysm and a fully developed aneurysm. The study shows that the material modeling of the vessel has a sizable effect on aneurysm initiation and fully developed aneurysms. Different material modeling of degeneration regions also affects the stressstrain response of aneurysm initiation. Additionally, the structural analysis without considering FSI (called noFSI) overestimates the peak von Mises stress by 52% at the interfaces of the layers.

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Section: Aneurysm Modelmentioning

confidence: 99%

mentioning

confidence: 99%

Investigation of material modeling in fluid–structure interaction analysis of an idealized three-layered abdominal aorta: aneurysm initiation and fully developed aneurysms

Şimşek

Kwon

2015

J Biol Phys

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“…In Fig. 5, a low relative error for wall stress obtained with the coarsest mesh is likely due to the fact that maximum stresses typically occur at highly curved regions, especially ones with a saddle point [29]. Piecewise linear facets cannot accurately model these surface details with coarse mesh sizes.…”

Section: Wall Extrusion Versus Mask Dilation Approachmentioning

confidence: 99%

The Importance of Patient-Specific Regionally Varying Wall Thickness in Abdominal Aortic Aneurysm Biomechanics

Raut

Jana

Oliveira

et al. 2013

Journal of Biomechanical Engineering

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Abdominal aortic aneurysm (AAA) is a vascular condition where the use of a biomechanics-based assessment for patient-specific risk assessment is a promising approach for clinical management of the disease. Among various factors that affect such assessment, AAA wall thickness is expected to be an important factor. However, regionally varying patient-specific wall thickness has not been incorporated as a modeling feature in AAA biomechanics. To the best our knowledge, the present work is the first to incorporate patient-specific variable wall thickness without an underlying empirical assumption on its distribution for AAA wall mechanics estimation. In this work, we present a novel method for incorporating regionally varying wall thickness (the "PSNUT" modeling strategy) in AAA finite element modeling and the application of this method to a diameter-matched cohort of 28 AAA geometries to assess differences in wall mechanics originating from the conventional assumption of a uniform wall thickness. For the latter, we used both a literature-derived population average wall thickness (1.5 mm; the "UT" strategy) as well as the spatial average of our patient-specific variable wall thickness (the "PSUT" strategy). For the three different wall thickness modeling strategies, wall mechanics were assessed by four biomechanical parameters: the spatial maxima of the first principal stress, strain, strain-energy density, and displacement. A statistical analysis was performed to address the hypothesis that the use of any uniform wall thickness model resulted in significantly different biomechanical parameters compared to a patient-specific regionally varying wall thickness model. Statistically significant differences were obtained with the UT modeling strategy compared to the PSNUT strategy for the spatial maxima of the first principal stress (p ¼ 0.002), strain (p ¼ 0.0005), and strain-energy density (p ¼ 7.83 e-5) but not for displacement (p ¼ 0.773). Likewise, significant differences were obtained comparing the PSUT modeling strategy with the PSNUT strategy for the spatial maxima of the first principal stress (p ¼ 9.68 e-7), strain (p ¼ 1.03 e-8), strain-energy density (p ¼ 9.94 e-8), and displacement (p ¼ 0.0059). No significant differences were obtained comparing the UT and PSUT strategies for the spatial maxima of the first principal stress (p ¼ 0.285), strain (p ¼ 0.152), strain-energy density (p ¼ 0.222), and displacement (p ¼ 0.0981). This work strongly recommends the use of patient-specific regionally varying wall thickness derived from the segmentation of abdominal computed tomography (CT) scans if the AAA finite element analysis is focused on estimating peak biomechanical parameters, such as stress, strain, and strain-energy density.

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“…It is often accompanied by the growth of ILT, and ILT formation has been linked to both the progression [1] and risk of rupture [2] of AAA. The mechanisms of ILT formation, as well as the influence of ILT on AAA biomechanics, however, are complex and poorly understood [3,4].…”

Section: Introductionmentioning

confidence: 99%

Mechanical Platelet Activation Potential in Abdominal Aortic Aneurysms

Hansen

Arzani

Shadden

2015

Journal of Biomechanical Engineering

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Intraluminal thrombus (ILT) in abdominal aortic aneurysms (AAA) has potential implications to aneurysm growth and rupture risk; yet, the mechanisms underlying its development remain poorly understood. Some researchers have proposed that ILT development may be driven by biomechanical platelet activation within the AAA, followed by adhesion in regions of low wall shear stress. Studies have investigated wall shear stress levels within AAA, but platelet activation potential (AP) has not been quantified. In this study, patient-specific computational fluid dynamic (CFD) models were used to analyze stressinduced AP within AAA under rest and exercise flow conditions. The analysis was conducted using Lagrangian particle-based and Eulerian continuum-based approaches, and the results were compared. Results indicated that biomechanical platelet activation is unlikely to play a significant role for the conditions considered. No consistent trend was observed in comparing rest and exercise conditions, but the functional dependence of AP on stress magnitude and exposure time can have a large impact on absolute levels of anticipated platelet AP. The Lagrangian method obtained higher peak AP values, although this difference was limited to a small percentage of particles that falls below reported levels of physiologic background platelet activation.

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The Role of Geometric and Biomechanical Factors in Abdominal Aortic Aneurysm Rupture Risk Assessment

Cited by 80 publications

References 98 publications

Investigation of material modeling in fluid–structure interaction analysis of an idealized three-layered abdominal aorta: aneurysm initiation and fully developed aneurysms

Investigation of material modeling in fluid–structure interaction analysis of an idealized three-layered abdominal aorta: aneurysm initiation and fully developed aneurysms

The Importance of Patient-Specific Regionally Varying Wall Thickness in Abdominal Aortic Aneurysm Biomechanics

Mechanical Platelet Activation Potential in Abdominal Aortic Aneurysms

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