4,697 research outputs found

    Modelling the evolution of cerebral aneurysms: biomechanics, mechanobiology and multiscale modelling

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    Intracranial aneurysms (IAs) are abnormal dilatations of the cerebral vasculature. Computational modelling may shed light on the aetiology of the disease and lead to improved criteria to assist diagnostic decisions. We briefly review models of aneurysm evolution to date and present a novel fluid-solid-growth (FSG) framework for patient-specific modelling of IA evolution. We illustrate its application to 4 clinical cases depicting an IA. The section of arterial geometry containing the IA is removed and replaced with a cylindrical section: this represents an idealised section of healthy artery upon which IA evolution is simulated. The utilisation of patient-specific geometries enables G&R to be explicitly linked to physiologically realistic spatial distributions and magnitudes of haemodynamic stimuli. In this study, we investigate the hypothesis that elastin degradation is driven by locally low wall shear stress (WSS). In 3 out of 4 cases, the evolved model IA geometry is qualitatively similar to the corresponding in vivo IA geometry. This suggests some tentative support for the hypothesis that low WSS plays a role in the mechanobiology of IA evolution

    Finite element and mechanobiological modelling of vascular devices

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    There are two main surgical treatments for vascular diseases, (i) percutaneous stent deployment and (ii) replacement of an atherosclerotic artery with a vascular graft or tissue engineered blood vessel. The aim of this thesis was to develop computational models that could assist in the design of vascular stents and tissue engineered vascular grafts and scaffolds. In this context, finite element (FE) models of stent expansion in idealised and patient specific models of atherosclerotic arteries were developed. Different modelling strategies were investigated and an optimal modelling approach was identified which minimised computational cost without compromising accuracy. Numerical models of thin and thick strut stents were developed using this modelling approach to replicate the ISAR-STEREO clinical trial and the models identified arterial stresses as a suitable measure of stent induced vascular injury. In terms of evaluating vascular graft performance, mechanical characterisation experiments can be conducted in order to develop constitutive models that can be used in FE models of vascular grafts to predict their mechanical behaviour in-situ. In this context, bacterial cellulose (BC), a novel biomaterial, was mechanically characterised and a constitutive model was developed to describe its mechanical response. In addition, the interaction of smooth muscle cells with BC was studied using cell culture experiments. The constitutive model developed for BC was used as an input for a novel multi-scale mechanobiological modelling framework. The mechanobiological model was developed by coupling an FE model of a vascular scaffold and a lattice free agent based model of cell growth dynamics and remodelling in vascular scaffolds. By comparison with published in-vivo and in-vitro works, the model was found to successfully capture the key characteristics of vascular remodelling. It can therefore be used as a predictive tool for the growth and remodelling of vascular scaffolds and graft

    Multiphase modelling of tumour growth and extracellular matrix interaction: mathematical tools and applications

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    Resorting to a multiphase modelling framework, tumours are described here as a mixture of tumour and host cells within a porous structure constituted by a remodelling extracellular matrix (ECM), which is wet by a physiological extracellular fluid. The model presented in this article focuses mainly on the description of mechanical interactions of the growing tumour with the host tissue, their influence on tumour growth, and the attachment/detachment mechanisms between cells and ECM. Starting from some recent experimental evidences, we propose to describe the interaction forces involving the extracellular matrix via some concepts coming from viscoplasticity. We then apply the model to the description of the growth of tumour cords and the formation of fibrosis

    New Developments in Tissue Engineering of Microvascular Prostheses

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    none3noneV. VINDIGNI; ABATANGELO G; BASSETTO FVindigni, Vincenzo; Abatangelo, Giovanni; Bassetto, Franc

    Mechanisms of Vascular Disease: A Reference Book for Vascular Specialists

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    New updated edition first published with Cambridge University Press. This new edition includes 29 chapters on topics as diverse as pathophysiology of atherosclerosis, vascular haemodynamics, haemostasis, thrombophilia and post-amputation pain syndromes

    A cellular automaton model for tumour growth in inhomogeneous environment

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    Most of the existing mathematical models for tumour growth and tumour-induced angiogenesis neglect blood flow. This is an important factor on which both nutrient and metabolite supply depend. In this paper we aim to address this shortcoming by developing a mathematical model which shows how blood flow and red blood cell heterogeneity influence the growth of systems of normal and cancerous cells. The model is developed in two stages. First we determine the distribution of oxygen in a native vascular network, incorporating into our model features of blood flow and vascular dynamics such as structural adaptation, complex rheology and red blood cell circulation. Once we have calculated the oxygen distribution, we then study the dynamics of a colony of normal and cancerous cells, placed in such a heterogeneous environment. During this second stage, we assume that the vascular network does not evolve and is independent of the dynamics of the surrounding tissue. The cells are considered as elements of a cellular automaton, whose evolution rules are inspired by the different behaviour of normal and cancer cells. Our aim is to show that blood flow and red blood cell heterogeneity play major roles in the development of such colonies, even when the red blood cells are flowing through the vasculature of normal, healthy tissue
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