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Subject = stent;
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Displaying Results 1 - 15 of 15 on page 1 of 1
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A computational and experimental investigation of the in-vivo biomechanics of the human aorta
(2020)
Concannon, Jamie
A computational and experimental investigation of the in-vivo biomechanics of the human aorta
(2020)
Concannon, Jamie
Abstract:
The overall objective of this thesis is to provide a new understanding of the degree of biomechanical heterogeneity that exists along the human aorta, against the backdrop of clinical literature reporting that patient outcomes depend on the distance of aortic repair from the heart. Spatial variance in human aortic bioarchitecture responsible for the elasticity of the vessel is poorly understood. We present a quantification of the constituents responsible for aortic compliance, namely, elastin, collagen and smooth muscle cells, using histological and stereological techniques along the vessel length. Using donated cadaveric tissue, a series of samples were excised between the proximal ascending aorta and the distal abdominal aorta, for five cadavers, each of which underwent various staining procedures to enhance specific constituents of the wall. Using polarised light microscopy techniques, the orientation of collagen fibres was studied for each location and each tunical layer of the ...
http://hdl.handle.net/10379/16050
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A full-range, multi-variable, CFD-based methodology to identify abnormal near-wall hemodynamics in a stented coronary artery
(2010)
Murphy, Jonathan; Boyle, Fergal
A full-range, multi-variable, CFD-based methodology to identify abnormal near-wall hemodynamics in a stented coronary artery
(2010)
Murphy, Jonathan; Boyle, Fergal
Abstract:
The benefit of coronary stent implantation is reduced by excessive intimal hyperplasia which re-narrows the artery and the prevention of which is still a primary concern for clinicians. Abnormal hemodynamics create non-physiological viscous stress on the artery wall, one of the root causes of intimal hyperplasia following stent implantation. A methodology to comprehensively evaluate the viscous stress on the artery wall following stent implantation would be useful to evaluate a stent’s hemodynamic performance. The proposed methodology employs 3D computational fluid dynamics, the variables wall shear stress (WSS), WSS gradient (WSSG), WSS angle gradient (WSSAG) and a statistical analysis to evaluate the viscous stress. The methodology is demonstrated and compared to a commonly used “threshold technique” for evaluating a stent’s hemodynamic performance. It is demonstrated that the threshold technique is not adequate to fully analyse the viscous stress on the artery wall and can even b...
https://arrow.dit.ie/engschmecart/18
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A robust anisotropic hyperelastic formulation for the modelling of soft tissue
(2018)
Nolan, D.R.; Gower, A.L.; Destrade, M.; Ogden, R.W.; McGarry, J.P.
A robust anisotropic hyperelastic formulation for the modelling of soft tissue
(2018)
Nolan, D.R.; Gower, A.L.; Destrade, M.; Ogden, R.W.; McGarry, J.P.
http://hdl.handle.net/10379/13146
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An anisotropic inelastic constitutive model to describe stress softening and permanent deformation in arterial tissue
(2012)
KELLY, DANIEL; MAHER, EOGHAN JOSEPH; LALLY, CAITRIONA
An anisotropic inelastic constitutive model to describe stress softening and permanent deformation in arterial tissue
(2012)
KELLY, DANIEL; MAHER, EOGHAN JOSEPH; LALLY, CAITRIONA
Abstract:
Inelastic phenomena such as softening and unrecoverable inelastic strains induced by loading have been observed experimentally in soft tissues such as arteries. These phenomena need to be accounted for in constitutive models of arterial tissue so that computational models can accurately predict the outcomes of interventional procedures such as balloon angioplasty and stenting that involve non-physiological loading of the tissue. In this study, a novel constitutive model is described that accounts for inelastic effects such as Mullins-type softening and permanent set in a fibre reinforced tissue. The evolution of inelasticity is governed by a set of internal variables. Softening is introduced through a typical continuum damage mechanics approach, while the inelastic residual strains are introduced through an additive split in the stress tensor. Numerical simulations of aorta and carotid arterial tissue subjected to uniaxial testing in the longitudinal, circumferential and axial direc...
http://hdl.handle.net/2262/63771
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Analysis of the mechanical performance of a biodegradable magnesium stent in a remodelling artery
(2019)
Boland, Enda L.
Analysis of the mechanical performance of a biodegradable magnesium stent in a remodelling artery
(2019)
Boland, Enda L.
Abstract:
Coronary stents made from degradable biomaterials such as magnesium alloy are an emerging technology in the treatment of coronary artery disease. Biodegradable stents provide mechanical support to the artery during the initial scaffolding period after which the artery will have remodelled. The subsequent resorption of the stent biomaterial by the body has potential to reduce the risk associated with long-term placement of these devices, such as in-stent restenosis, late stent thrombosis, and fatigue fracture. Computational modelling such as finite-element analysis has proven to be an extremely useful tool in the continued design and development of these medical devices. What is lacking in computational modelling literature is the representation of the active response of the arterial tissue in the weeks and months following stent implantation, i.e., neointimal remodelling. The phenomenon of neointimal remodelling is particularly interesting and significant in the case of biodegradabl...
http://hdl.handle.net/10379/14970
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Comparison of in vitro human endothelial cell response to self-expanding stent deployment in a straight and curved peripheral artery simulator
(2018)
Ghriallais, R. N.; McNamara, L.; Bruzzi, M.
Comparison of in vitro human endothelial cell response to self-expanding stent deployment in a straight and curved peripheral artery simulator
(2018)
Ghriallais, R. N.; McNamara, L.; Bruzzi, M.
Abstract:
Haemodynamic forces have a synergistic effect on endothelial cell (EC) morphology, proliferation, differentiation and biochemical expression profiles. Alterations to haemodynamic force levels have been observed at curved regions and bifurcations of arteries but also around struts of stented arteries, and are also known to be associated with various vascular pathologies. Therefore, curvature in combination with stenting might create a pro-atherosclerotic environment compared with stenting in a straight vessel, but this has never been investigated. The goal of this study was to compare EC morphology, proliferation and differentiation within in vitro models of curved stented peripheral vessel models with those of straight and unstented vessels. These models were generated using both static conditions and also subjected to 24 h of stimulation in a peripheral artery bioreactor. Medical-grade silicone tubes were seeded with human umbilical vein endothelial cells to produce pseudovessels t...
http://hdl.handle.net/10379/13122
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Computational modelling of the degradation of poly-L-lactide for a bioresorbable polymeric stent
(2020)
Shine, Rosa Connor
Computational modelling of the degradation of poly-L-lactide for a bioresorbable polymeric stent
(2020)
Shine, Rosa Connor
Abstract:
The interest in biodegradable polymers for the design of bioresorbable stents, temporary vascular scaffolds designed to restore patency to obstructed vessels, has witnessed a dramatic growth over the last ten to fifteen years. While bioresorbable polymeric stents (BPS) offer possibilities to help address the long-term complications (e.g. in-stent restenosis, stent thrombosis) associated with permanent devices, in-vivo degradation behaviours are not yet fully understood. The application of computational modelling, for example finite element analysis (FEA), to predict and analyse BPS degradation behaviour provides a means to investigate in-vivo performance and further enhance BPS design. Current computational modelling techniques for the degradation of BPS predominately focus on the phenomenological aspects of degradation, with little emphasis given to the inherent microstructure changes (bulk degradation, crystallisation) which occur in the degrading polymer. This research aims to ad...
http://hdl.handle.net/10379/15956
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Computational Structural Modelling of Coronary Stent Deployment: A Review
(2010)
Martin, David; Boyle, Fergal
Computational Structural Modelling of Coronary Stent Deployment: A Review
(2010)
Martin, David; Boyle, Fergal
Abstract:
The finite element (FE) method is a powerful investigative tool in the field of biomedical engineering, particularly in the analysis of medical devices such as coronary stents whose performance is extremely difficult to evaluate in vivo. In recent years, a number of FE studies have been carried out to simulate the deployment of coronary stents, and the results of these studies have been utilised to assess and optimise the performance of these devices. The aim of this paper is to provide a thorough review of the state-of-the-art research in this area, discussing the aims, methods and conclusions drawn from a number of significant studies. It is intended that this paper will provide a valuable reference for future research in this area
https://arrow.dit.ie/engschmecart/35
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Finite Element Analysis of Balloon-Expandable Coronary Stent Deployment: Influence of Angioplasty Balloon Configuration
(2013)
Martin, David; Boyle, Fergal
Finite Element Analysis of Balloon-Expandable Coronary Stent Deployment: Influence of Angioplasty Balloon Configuration
(2013)
Martin, David; Boyle, Fergal
Abstract:
Today, the majority of coronary stents are balloon-expandable and are deployed using a balloon-tipped catheter. To improve deliverability, the membrane of the angioplasty balloon is typically folded about the catheter in a pleated configuration. As such, the deployment of the angioplasty balloon is governed by the material properties of the balloon membrane, its folded configuration and its attachment to the catheter. Despite this observation, however, an optimum strategy for modelling the configuration of the angioplasty balloon in finite element studies of coronary stent deployment has not been identified, and idealised models of the angioplasty balloon are commonly employed in the literature. These idealised models often neglect complex geometrical features, such as the folded configuration of the balloon membrane and its attachment to the catheter, which may have a significant influence on the deployment of a stent. In this study, three increasingly sophisticated models of a typ...
https://arrow.dit.ie/engschmecart/34
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Kinetics of endothelialization of the multilayer flow modulator and single-layer arterial stents
(2018)
Sultan, Sherif; Kavanagh, Edel P; Bonneau, Michel; Kang, Chantal; Alves, Antoine; Hynes...
Kinetics of endothelialization of the multilayer flow modulator and single-layer arterial stents
(2018)
Sultan, Sherif; Kavanagh, Edel P; Bonneau, Michel; Kang, Chantal; Alves, Antoine; Hynes, Niamh M
Abstract:
The multilayer flow modulator (MFM; Cardiatis, Isnes, Belgium) is a self-expandable mesh of braided cobalt alloy wires, used for treatment of aortic and peripheral aneurysms. To further improve our understanding of this novel technology, the endothelialization kinetics of the MFM was investigated and compared with those of two marketed single-layer stents. Five porcine animal models were used in which a total of 19 stents were implanted in the iliac and carotid arteries between one and five weeks before sacrifice. All 19 stents were successfully delivered. For all devices, nonsignificant signs of inflammation or thrombosis were noted, and there was no evidence of local intolerance. The MFM developed a thin layer of endothelial cells earlier and was associated with less neointimal development than the two single-layer stents. A differing phenomenon of integration was also revealed and hypothesized as endothelialization from adhesion of circulating endothelial progenitor cells, as wel...
http://hdl.handle.net/10379/14067
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Numerical simulation of stent angioplasty with predilation: an investigation into lesion constitutive representation and calcification influence
(2018)
Conway, C.; McGarry, J. P.; Edelman, E. R.; McHugh, P. E.
Numerical simulation of stent angioplasty with predilation: an investigation into lesion constitutive representation and calcification influence
(2018)
Conway, C.; McGarry, J. P.; Edelman, E. R.; McHugh, P. E.
Abstract:
It is acceptable clinical practice to predilate a severely occluded vessel to allow better positioning of endovascular stents, and while the impact of this intervention has been examined for aggregate response in animals there has been no means to examine whether there are specific vessels that might benefit. Finite element methods offer the singular ability to explore the mechanical response of arteries with specific pathologic alterations in mechanics to stenting and predilation. We examined varying representations of atherosclerotic tissue including homogeneous and heterogeneous dispersion of calcified particles, and elastic, pseudo-elastic, and elastic-plastic constitutive representations of bulk atherosclerotic tissue. The constitutive representations of the bulk atherosclerotic tissue were derived from experimental test data and highlight the importance of accounting for testing mode of loading. The impact of arterial predilation is presented and, in particular, its effect on ...
http://hdl.handle.net/10379/10888
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Sequential Structural and Fluid Dynamics Analysis of Balloon-Expandable Coronary Stents: A Multivariable Statistical Analysis
(2015)
Martin, David; Boyle, Fergal
Sequential Structural and Fluid Dynamics Analysis of Balloon-Expandable Coronary Stents: A Multivariable Statistical Analysis
(2015)
Martin, David; Boyle, Fergal
Abstract:
Several clinical studies have identified a strong correlation between neointimal hyperplasia following coronary stent deployment and both stent-induced arterial injury and altered vessel hemodynamics. As such, the sequential structural and fluid dynamics analysis of balloon-expandable stent deployment should provide a comprehensive indication of stent performance. Despite this observation, very few numerical studies of balloon-expandable coronary stents have considered both the mechanical and hemodynamic impact of stent deployment. Furthermore, in the few studies that have considered both phenomena, only a small number of stents have been considered. In this study, a sequential structural and fluid dynamics analysis methodology was employed to compare both the mechanical and hemodynamic impact of six balloon-expandable coronary stents. To investigate the relationship between stent design and performance, several common stent design properties were then identified and the dependence ...
https://arrow.dit.ie/engschmecart/45
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The Development of a Computational Test-Bed to Assess Coronary Stent Implantation
(2013)
Conway, Claire
The Development of a Computational Test-Bed to Assess Coronary Stent Implantation
(2013)
Conway, Claire
Abstract:
The implantation behaviour of coronary stents is of great interest to clinicians and engineers alike as in-stent restenosis (ISR) remains a critical issue with the community. ISR is hypothesized to occur for reasons that include injury to the vessel wall caused by stent placement. To reduce the incidence of ISR, improved design and testing of coronary stents is needed. This research aims to facilitate more comprehensive evaluation of stents in the design phase, by generating more realistic arterial environments and corresponding stress states than have been considered heretofore, as a step towards reducing the prevalence of ISR. Furthermore, it proposes improvements to the current requirements for coronary stent computational stress analyses as set out by the Food and Drug Administration (FDA). A systematic geometric test-bed with varying levels of arterial curvature and stenosis severity is developed and used to evalu...
http://hdl.handle.net/10379/3749
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Total ellipse of the heart valve: the impact of eccentric stent distortion on the regional dynamic deformation of pericardial tissue leaflets of a transcatheter aortic valve replacement
(2018)
Gunning, Paul S.; Saikrishnan, Neelakantan; Yoganathan, Ajit P.; McNamara, Laoise M.
Total ellipse of the heart valve: the impact of eccentric stent distortion on the regional dynamic deformation of pericardial tissue leaflets of a transcatheter aortic valve replacement
(2018)
Gunning, Paul S.; Saikrishnan, Neelakantan; Yoganathan, Ajit P.; McNamara, Laoise M.
Abstract:
Transcatheter aortic valve replacements (TAVRs) are a percutaneous alternative to surgical aortic valve replacements and are used to treat patients with aortic valve stenosis. This minimally invasive procedure relies on expansion of the TAVR stent to radially displace calcified aortic valve leaflets against the aortic root wall. However, these calcium deposits can impede the expansion of the device causing distortion of the valve stent and pericardial tissue leaflets. The objective of this study was to elucidate the impact of eccentric TAVR stent distortion on the dynamic deformation of the tissue leaflets of the prosthesis in vitro. Dual-camera stereophotogrammetry was used to measure the regional variation in strain in a leaflet of a TAVR deployed in nominal circular and eccentric (eccentricity index = 28%) orifices, representative of deployed TAVRs in vivo. It was observed that (i) eccentric stent distortion caused incorrect coaptation of the leaflets at peak diastole resulting i...
http://hdl.handle.net/10379/11760
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Wireless accelerometers for early detection of restenosis
(2018)
Jackson, Nathan; O’Keeffe, Rosemary; O’Leary, Robert; O’Neill, Mike; Moriarty, Micheál;...
Wireless accelerometers for early detection of restenosis
(2018)
Jackson, Nathan; O’Keeffe, Rosemary; O’Leary, Robert; O’Neill, Mike; Moriarty, Micheál; Mathewson, Alan
http://hdl.handle.net/10379/12061
Displaying Results 1 - 15 of 15 on page 1 of 1
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Institution
Dublin Institute of Technology (4)
NUI Galway (10)
Trinity College Dublin (1)
Item Type
Doctoral thesis (4)
Journal article (11)
Peer Review Status
Peer-reviewed (1)
Unknown (14)
Year
2020 (2)
2019 (1)
2018 (6)
2015 (1)
2013 (2)
2012 (1)
2010 (2)
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