Collagen Organization and Biomechanics of the Arteries and Aneurysms of the Human Brain

Canham, Peter B.; Korol, Renée; Finlay, Helen M.; Hammond, Rob; Holdsworth, D. W.; Ferguson, Gary G.; Lucas, Alexandra

doi:10.1007/3-540-31184-x_22

Cited by 8 publications

(10 citation statements)

References 34 publications

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“…In the predicted stress distributions over the aneurysmal surface, the peak stress always appears at the fundus, which makes sense since real aneurysms tend to rupture at this location (Canham et al, 2006). The ultimate stress of tissues from cerebral aneurysms have been experimentally obtained, and this fact allowed us to predict the size range for which the aneurysm could be expected to fail, see Fig.…”

Section: Discussion and Concluding Remarksmentioning

confidence: 96%

“…About 50% of patients die within one month after the event, and of those who survive more than one third have major neurologic deficits (Brisman et al, 2006;Schievink, 1997). Aneurysms are a common pathology only in human arteries and in some primates A c c e p t e d m a n u s c r i p t (Canham et al, 2006), and intracranial aneurysms are more prevalent in females than in males (Mettinger, 1982). Intracranial aneurysms usually do not rupture if they are less than 10 mm in diameter (Austin et al, 1993;Rinkel et al, 1998;Wiebers et al, 1981), and at clinical centres, cerebral aneurysms are considered as critical when their size is roughly larger than 5 mm.…”

Section: Introductionmentioning

confidence: 99%

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A theoretical model for fibroblast-controlled growth of saccular cerebral aneurysms

Kroon

Holzapfel

2009

Journal of Theoretical Biology

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A new theoretical model for the growth of saccular cerebral aneurysms is proposed by extending the recent constitutive framework of Kroon and Holzapfel (J. Theor. Biol., 247:775-787, 2007). The continuous turnover of collagen is taken to be the driving mechanism in aneurysmal growth. The collagen production rate depends on the magnitude of the cyclic deformation of fibroblasts, caused by the pulsating blood pressure during the cardiac cycle. The volume density of fibroblasts in the aneurysmal tissue is taken to be constant throughout the growth process. The growth model is assessed by considering the inflation of an axisymmetric membranous piece of aneurysmal tissue, with material characteristics representative of a cerebral aneurysm. The diastolic and systolic states of the aneurysm are computed, together with its load-free state. It turns out that the value of collagen pre-stretch, that determines growth speed and stability of the aneurysm, is of pivotal importance. The model is able to predict aneurysms with typical berry-like shapes observed clinically, and the predicted wall stresses correlate well with the experimentally obtained ultimate stresses of this type of tissue. The model predicts that aneurysms should fail when reaching a size of about 1.2-3.6 mm, which is smaller than what has been clinically observed. With some refinements, the model may, however, be used to predict future growth of diagnosed aneurysms.

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Section: Discussion and Concluding Remarksmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

A theoretical model for fibroblast-controlled growth of saccular cerebral aneurysms

Kroon

Holzapfel

2009

Journal of Theoretical Biology

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“…Grasping the mechanical properties of cerebrovascular lesions ex vivo is equally challenging because of the imperative to manipulate small, highly anisotropic 18 , and fresh human tissue samples of limited availability - preservation with fixation for later analysis is not an option as tissue mechanical properties are modified in the processing. Furthermore, though a map of sample thickness is necessary to translate a force into a stress, there is no valid method to map thickness in vivo , which varies in space – ranging from 16 to 500 microns in the unloaded state 19, 20 – and time during the progression of the disease.…”

Section: Computational Fluid Dynamicsmentioning

confidence: 99%

Role of Fluid Dynamics and Inflammation in Intracranial Aneurysm Formation

2014

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The emergence of inflammation as a key mediator of aneurysmogenesis provides new opportunities to understand the processes underlying development of intracranial aneurysms (IA). Inflammation unifies the triptych influences of alterations in local flow, mechanical properties of the wall and biochemical mediators and opens new avenues for building robust predictive tools. This review discusses the impact of the inflammatory cascade during the formation of intracranial aneurysms, and its associated morphological, structural and mechanical changes especially in the setting of flow-induced endothelial dysfunction.

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“…They are especially prevalent in the thoracic artery, the abdominal aorta and the arterial circle of Willis at the base of the brain. In the cerebral vasculature, the saccular type of aneurysm dominates and is mainly found in the branching regions of the circle of Willis (Austin et al 1993;MacDonald et al 2000;Canham et al 2006). The saccular cerebral aneurysm tends to form a sac-like expansion of the parent artery.…”

Section: Introductionmentioning

confidence: 99%

Estimation of the distributions of anisotropic, elastic properties and wall stresses of saccular cerebral aneurysms by inverse analysis

Kroon

Holzapfel

2008

Proc. R. Soc. A.

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A new method is proposed for estimating the elastic properties of the inhomogeneous and anisotropic structure of saccular cerebral aneurysms by inverse analysis. The aneurysm is modelled as a membrane and the constitutive response of each individual layer of the passive tissue is characterized by a transversely isotropic strain energy function of exponential type. The collagen fibres in the aneurysm wall are assumed to govern the mechanical response. Four parameters characterize the constitutive behaviour of the tissue: two initial stiffnesses of the collagen fabric in the two in-plane principal directions, one parameter describing the degree of nonlinearity that the collagen fibres exhibit and the other structural parameter, i.e. the angle which defines the orientation of the collagen fibres. The parameter describing the fibre nonlinearity is assumed to be constant, while all others are assumed to vary continuously over the aneurysm surface. Two model aneurysms, with the same initial geometry, boundary and loading conditions, constitutive behaviour and finite-element discretization, are defined: a 'reference model' with known distributions of material and structural properties and an 'estimation model' whose properties are to be estimated. An error function is defined quantifying the deviations between the deformations from the reference and the estimation models. The error function is minimized with respect to the unknown parameters in the estimation model, and in this way the reference parameter distributions are re-established. In order to achieve a robust parameter estimation, a novel element partition method is employed. The accordance between the estimated and the reference distributions is satisfactory. The deviations of the maximum stress distributions between the two models are below 1%. Consequently, the wall stresses in the cerebral aneurysm estimated by inverse analysis are accurate enough to facilitate the assessment of the risk of aneurysm rupture.

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Collagen Organization and Biomechanics of the Arteries and Aneurysms of the Human Brain

Cited by 8 publications

References 34 publications

A theoretical model for fibroblast-controlled growth of saccular cerebral aneurysms

A theoretical model for fibroblast-controlled growth of saccular cerebral aneurysms

Role of Fluid Dynamics and Inflammation in Intracranial Aneurysm Formation

Estimation of the distributions of anisotropic, elastic properties and wall stresses of saccular cerebral aneurysms by inverse analysis

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