Diversity in the Strength and Structure of Unruptured Cerebral Aneurysms

Robertson, Anne M.; Duan, Xiaoyu; Aziz, Khaled; Hill, Michael R.S.; Watkins, Simon C.; Cebral, Juan R.

doi:10.1007/s10439-015-1252-4

Cited by 84 publications

(90 citation statements)

References 37 publications

(49 reference statements)

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“…Mechanical tests of human aneurysm samples have suggested the stiffness of the wall may be associated to rupture 7 . It has also been shown that both wall structure and mechanical strength can vary from patient to patient even within the unruptured population, and that wall structure can also vary locally within the same aneurysm 23 . Furthermore, two subpopulations have been found in a study of unruptured aneurysms, one with weaker more vulnerable walls and another with stronger walls 23 .…”

Section: Introductionmentioning

confidence: 99%

“…It has also been shown that both wall structure and mechanical strength can vary from patient to patient even within the unruptured population, and that wall structure can also vary locally within the same aneurysm 23 . Furthermore, two subpopulations have been found in a study of unruptured aneurysms, one with weaker more vulnerable walls and another with stronger walls 23 . Additionally, possible associations between global aneurysm hemodynamic characteristics and wall strength and stiffness have been identified 5 .…”

Section: Introductionmentioning

confidence: 99%

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Regional Mapping of Flow and Wall Characteristics of Intracranial Aneurysms

et al. 2016

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The evolution of intracranial aneurysms (IAs) is thought to be driven by progressive wall degradation in response to abnormal hemodynamics. Previous studies focused on the relationship between global hemodynamics and wall properties. However, hemodynamics, wall structure and mechanical properties of cerebral aneurysms can be non-uniform across the aneurysm wall. Therefore, the aim of this work is to introduce a methodology for mapping local hemodynamics to local wall structure in resected aneurysm specimens. This methodology combines image-based computational fluid dynamics, tissue resection, micro-CT imaging of resected specimens mounted on 3D-printed aneurysm models, alignment to 3D vascular models, multi-photon microscopy of the wall, and regional mapping of hemodynamics and wall properties. This approach employs a new 3D virtual marking tool for surgeons to delineate the location of the resected specimen directly on the 3D model, while in the surgical suite. The case of a middle cerebral artery aneurysm is used to illustrate the application of this methodology to the assessment of the relationship between local wall shear stress and local wall properties including collagen fiber organization and wall geometry. This methodology can similarly be used to study the relationship between local intramural stresses and local wall structure.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Regional Mapping of Flow and Wall Characteristics of Intracranial Aneurysms

et al. 2016

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“…To the authors' knowledge, no biaxial mechanical data combined with the corresponding microstructure of both healthy (layer-specific) and aneurysmatic aortic tissues are yet available. To further increase the understanding and to improve rupture risk prediction it is necessary to study effects of localized wall changes (shown, for example, for cerebral aneurysms in [38]) by combining the microstructure with patient-specific mechanical data and systematically compare these changes with healthy abdominal aortic tissues. Such a knowledge can then be used to improve numerical models incorporating structurebased nonlinear material models, as was recently performed in [39] where the biaxial response of porcine aortic tissues was combined with the related microstructure identified using histological slices.…”

Section: Introductionmentioning

confidence: 99%

Microstructure and mechanics of healthy and aneurysmatic abdominal aortas: experimental analysis and modelling

Niestrawska

Viertler

Regitnig

et al. 2016

J. R. Soc. Interface.

158

178

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Soft biological tissues such as aortic walls can be viewed as fibrous composites assembled by a ground matrix and embedded families of collagen fibres. Changes in the structural components of aortic walls such as the ground matrix and the embedded families of collagen fibres have been shown to play a significant role in the pathogenesis of aortic degeneration. Hence, there is a need to develop a deeper understanding of the microstructure and the related mechanics of aortic walls. In this study, tissue samples from 17 human abdominal aortas (AA) and from 11 abdominal aortic aneurysms (AAA) are systematically analysed and compared with respect to their structural and mechanical differences. The collagen microstructure is examined by analysing data from second-harmonic generation imaging after optical clearing. Samples from the intact AA wall, their individual layers and the AAA wall are mechanically investigated using biaxial stretching tests. A bivariate von Mises distribution was used to represent the continuous fibre dispersion throughout the entire thickness, and to provide two independent dispersion parameters to be used in a recently proposed material model. Remarkable differences were found between healthy and diseased tissues. The out-of-plane dispersion was significantly higher in AAA when compared with AA tissues, and with the exception of one AAA sample, the characteristic wall structure, as visible in healthy AAs with three distinct layers, could not be identified in AAA samples. The collagen fibres in the abluminal layer of AAAs lost their waviness and exhibited rather straight and thick struts of collagen. A novel set of three structural and three material parameters is provided. With the structural parameters fixed, the material model was fitted to the mechanical experimental data, giving a very satisfying fit although there are only three material parameters involved. The results highlight the need to incorporate the structural differences into finite-element simulations as otherwise simulations of AAA tissues might not be good predictors for the actual in vivo stress state.

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“…The adverse flow conditions described above have been previously shown to be associated with aneurysm wall inflammation which itself is associated with aneurysm rupture 27 , wall weakening and stiffening characteristic of vulnerable walls 28, 29 , and damaged collagen architectures 30 . Additionally, these flow conditions have been associated with aneurysm rupture 31 .…”

Section: Discussionmentioning

confidence: 95%

Hemodynamic Characteristics of Ruptured and Unruptured Multiple Aneurysms at Mirror and Ipsilateral Locations

Doddasomayajula

Chung

Mut

et al. 2017

AJNR Am J Neuroradiol

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Background and Purpose Different hemodynamic patterns have been associated with aneurysm rupture. The objective was to test whether hemodynamic characteristics of the ruptured aneurysm in patients with multiple aneurysms were different from unruptured aneurysms of the same patient. Materials and Methods A total of 24 mirror and 58 ipsilateral multiple aneurysms with one ruptured and the other(s) unruptured were studied. Computational fluid dynamics models were created from 3D angiographies. Case-control studies of mirror and ipsilateral aneurysms were performed using paired Wilcoxon tests. Results In mirror pairs, the ruptured aneurysm had more oscillatory wall shear stress (WSS) (p=0.007) than the unruptured one, and tended to be more elongated (higher aspect ratio), although this trend only achieved marginal significance (p=0.0302 one-sided test). In ipsilateral aneurysms, ruptured aneurysms had larger maximum WSS (p=0.0501), more concentrated (p=0.0007) and oscillatory WSS (p=0.0001), stronger (p=0.0001) and more concentrated inflow jets (p=0.0001), larger maximum velocity (p=0.0003), and more complex flow patterns (p=0.0001) compared to unruptured aneurysms. Additionally, ruptured aneurysms were larger (p=0.0001), more elongated (p=0.0001), had wider necks (p=0.0003), and lower minimum WSS (p=0.0002) than unruptured aneurysms. Conclusions High WSS oscillations and larger aspect ratios are associated with rupture in mirror aneurysms. Adverse flow conditions characterized by high and concentrated inflow jets, high, concentrated and oscillatory WSS, and strong, complex and unstable flow patterns are associated with rupture in ipsilateral multiple aneurysms. In multiple ipsilateral aneurysms, these unfavorable flow conditions are more likely to develop in larger, more elongated, wider necked, and more distal aneurysms.

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Diversity in the Strength and Structure of Unruptured Cerebral Aneurysms

Cited by 84 publications

References 37 publications

Regional Mapping of Flow and Wall Characteristics of Intracranial Aneurysms

Regional Mapping of Flow and Wall Characteristics of Intracranial Aneurysms

Microstructure and mechanics of healthy and aneurysmatic abdominal aortas: experimental analysis and modelling

Hemodynamic Characteristics of Ruptured and Unruptured Multiple Aneurysms at Mirror and Ipsilateral Locations

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