Dissertations / Theses on the topic 'Haemodynamics'
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1
O'Brien, Aoife Bernadette. "Pulmonary Haemodynamics." Thesis, Imperial College London, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.398251.
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Leunissen, Karel Maria Lucas. "Haemodynamics during haemodialysis." Maastricht : Maastricht : Rijksuniversiteit Limburg ; University Library, Maastricht University [Host], 1988. http://arno.unimaas.nl/show.cgi?fid=5410.
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Peacock, J. A. "Heart valve haemodynamics." Thesis, University of Oxford, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.371560.
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Begbuna, Veronica. "Haemodynamics in chronic venous disease." Thesis, Imperial College London, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.401816.
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Zabielski, Leszek. "Helical pipe flow in haemodynamics." Thesis, Imperial College London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.338931.
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Moorhead, Katherine Tracey. "Autoregulation modelling of cerebral haemodynamics." Thesis, University of Canterbury. Mechanical Engineering, 2005. http://hdl.handle.net/10092/6844.
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The Circle of Willis (CoW) is a ring-like structure of blood vessels found at the base of the brain. Its main function is to distribute a constant flow oxygen-rich arterial blood to the cerebral mass, despite changes in afferent pressures or flows. This objective is achieved by a local mechanism known as autoregulation, whereby the resistance in small vessels branching from the CoW changes by vasodilation or vasoconstriction of the smooth muscle cells surrounding the vessel.
A one-dimensional (1D) model of the CoW is developed to simulate a series of possible clinical scenarios such as occlusions in afferent arteries, absent or string-like circulus vessels, or arterial infarctions. A series of studies investigates various features of autoregulatory behaviour. Firstly, a simple model is created to verify solution methods; secondly, the model is validated against a three-dimensional (3D) Computational Fluid Dynamics (CFD) model; and lastly, the decentralised nature of cerebral autoregulation is investigated. Finally, an advanced, metabolic model of autoregulation is created, incorporating the successful aspects of the early model, as well as more physiologically accurate dynamics.
The advanced model captures cerebral haemodynamic autoregulation by using a Proportional-Integral-Derivative (PID) controller to modify efferent artery resistances and partial pressures of oxygen to maintain optimal efferent flow rates and oxygen supply to the cerebral mass for a given circle geometry and afferent blood pressure. This advanced model is physiologically relevant, matching the accepted physiological responses of blood flow as a function of arterial pressure, tissue oxygen partial pressure as a function of blood flow, as well as limited transient clinical data.
Results match accepted physiological response and exhibit excellent correlation with the limited clinical data available. In addition, a set of boundary conditions and geometry is presented for which the autoregulated system cannot provide the necessary efferent flow rates and perfusion, representing a condition with increased risk of stroke and highlighting the importance of modelling the haemodynamics of the Circle of Willis. The system model created is computationally simple so it can be used to identify at-risk cerebral arterial geometries and conditions prior to surgery or other clinical procedures. In addition, the solution for the CoW arterial system is obtained in a far shorter time period using this time-varying resistance model than with higher dimensional CFD methods, and requires significantly less computational effort while retaining a high level of accuracy.
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Dalton, Matthew W. "Experimental modelling of vascular haemodynamics." Thesis, Nottingham Trent University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.273762.
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Dury, R. J. "Understanding haemodynamics in neurodegenerative disease." Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/50380/.
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In this thesis, the haemodynamic, functional and structural changes in Alzheimer's Disease, Huntington's Disease and Multiple Sclerosis are assessed at 7T. Across all chapters, there is a focus on the use of Arterial Spin Labelling (ASL) to provide haemodynamic measures of perfusion (or cerebral blood flow) and transit time (TT) to provide a useful marker of disease. Arterial Spin Labelling (ASL) has the advantage that it is a non-invasive method to measure perfusion using magnetic resonance imaging (MRI). Clinically, perfusion is assessed using contrast-enhanced techniques which requires the intravenous administration of an exogenous gadolinium-based contrast agent, such as Prohance-TM and Gadovist-TM. Contrast-enhanced techniques typically provide higher SNR than ASL methods, however the non-invasive nature of ASL makes it a safe method suited for repeated measures in any subjects, including those with poor renal clearance. Additionally, gadolinium contrast agents have been shown to accumulate in neuronal tissue, and until the clinical significance of this is determined, contrast-enhanced scans should be performed with caution. In Chapter 5, arterial spin labelling is used to assess cerebral perfusion in a patient group with Alzheimer's Disease (AD) and compared with an age-matched healthy control group (HC). Functional MRI (fMRI) is used to assess functional connectivity within the default mode network (DMN) and measures compared between the AD and HC group. In addition, high resolution structural data is acquired to assess the effects of atrophy in AD. Results demonstrate a significant decrease in grey matter perfusion and a significant increase in grey matter transit time in the AD group compared the HC group. A trend showing a decrease in functional connectivity in the DMN was found in the AD group as compared to the HC group. As expected, significant grey matter loss and cortical thinning were observed in the AD group compared to the HC group. Secondly, haemodynamic and vascular changes in a Huntington's Disease (HD) patient group are assessed and compared with healthy age matched controls (HC). Phase contrast angiography is used to assess vessel density and vessel radius distributions between the two groups. Structural data was also acquired to assess grey matter volume and cortical thickness differences between the two groups. A significant reduction in perfusion was found in grey matter, putamen and the caudate in the HD group compared to the HC group. The ASL transit time was found to be significantly increased in the caudate and putamen in the HD group compared to the HC group. Phase contrast angiography data showed an increase in the frequency of smaller vessels (0.15-0.35mm) in the HD group compared to the HC group, whereas larger vessels appeared more frequently in the HC group. A significant reduction in grey matter volume was also observed in the HD group compared to the HC group, which manifested as thinning of the cortical ribbon. In the final study of this thesis, high spatial resolution arterial spin labelling is used to assess perfusion inside cortical lesions and compare with perfusion in surrounding normal appearing grey matter in a Multiple Sclerosis (MS) patient group. Grey matter perfusion as a function of distance from the cortical lesions was also assessed. It was found that cortical lesions have reduced perfusion compared to surrounding normal appearing grey matter. Perfusion increased and stabilised immediately outside of the cortical lesion itself, suggesting that the perfusion deficit observed is highly spatially localised.
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Williams, Stephen A. "Microvascular haemodynamics in essential hypertension." Thesis, Imperial College London, 1989. http://hdl.handle.net/10044/1/47712.
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Hall, Emma Louise. "Quantitative methods to assess cerebral haemodynamics." Thesis, University of Nottingham, 2012. http://eprints.nottingham.ac.uk/12673/.
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In this thesis methods for the assessment of cerebral haemodynamics using 7 T Magnetic Resonance Imaging (MRI) are described. The measurement of haemodynamic parameters, such as cerebral blood flow (CBF), is an important clinical tool. Arterial Spin Labelling (ASL) is a non-invasive technique for CBF measurement using MRI. ASL methodology for ultra high field (7 T) MRI was developed, including investigation of the optimal readout strategy. Look-Locker 3D-EPI is demonstrated to give large volume coverage improving on previous studies. Applications of methods developed to monitor functional activity, through flow or arterial blood volume, in healthy volunteers and in patients with low grade gliomas using Look-Locker ASL are described. The effect of an increased level of carbon dioxide in the blood (hypercapnia) was studied using ASL and functional MRI; hypercapnia is a potent vasodilator and has a large impact on haemodynamics. These measures were used to estimate the increase in oxygen metabolism associated with a simple motor task. To study the physiology behind the hypercapnic response, magnetoencephalography was used to measure the impact of hypercapnia on neuronal activity. It was shown that hypercapnia induces widespread desynchronisation in a wide frequency range, up to ~ 50 Hz, with peaks in the sensory-motor areas. This suggests that hypercapnia is not iso-metabolic, which is an assumption of calibrated BOLD. A Look-Locker gradient echo sequence is described for the quantitative monitoring of a gadolinium contrast agent uptake through the change in longitudinal relaxation rate. This sequence was used to measure cerebral blood volume in Multiple Sclerosis patients. Further development of the sequence yielded a high resolution anatomical scan with reduced artefacts due to field inhomogeneities associated with ultra high field imaging. This allows whole head images acquired at sub-millimetre resolution in a short scan time, for application in patient studies.
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Hull, James H. K. "Large artery haemodynamics in cystic fibrosis." Thesis, Kingston University, 2010. http://eprints.kingston.ac.uk/20343/.
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Cystic Fibrosis (CF) is the most common lethal autosomal recessive condition and affects approximately 1/2500 Caucasian newborns in the United Kingdom and 70,000 individuals worldwide. The gene defect classically leads to a phenotype comprising significant respiratory I and gastrointestinal manifestations, however is recognised to have multisystem consequences. Over the past 70 years there has been considerable progress in the understanding and treatment of CF such that it has moved from a poorly understood condition, almost universally fatal in infancy, to a complex multisystem disorder now affecting as many adults as children. This 'evolution' of the disease presents new challenges for clinicians and has increased focus on its extra-pulmonary components. In the general population cardiovascular disease is the leading cause of morbidity and mortality and it is now recognised that progressive changes in the structure and function of the large arterial system are a key determinant of this association. Furthermore these changes lead to alterations in large artery haemodynamics which have immediate physiological relevance for myocardial work and oxygen demand but also perfusion of the distal organs. Modern techniques permit large artery haemodynamics to be evaluated simply and effectively using the non-invasive technique of applanation tonometry with pulse wave analysis. The overall aim of this thesis was to use this technique to provide an evaluation of large artery haemodynamics in a cohort of adult patients with CF. The experimental work in this thesis includes a study assessing the validity of the haemodynamic techniques used in this thesis (study A) and three studies evaluating large artery haemodynamics in patients with CF; at rest (study I), in response to exercise (study II) and finally following a therapeutic intervention (study III).
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Carlisle, K. M. "Hepatic haemodynamics in health and disease." Thesis, University of Bristol, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261289.
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Kolachalama, Vijaya B. "Predictive haemodynamics of the human carotid artery." Thesis, University of Southampton, 2006. https://eprints.soton.ac.uk/41804/.
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This thesis employs parametrically defined geometry of the human carotid artery bifurcation to better understand the relationship between a range of parameters and the associated haemodynamics and to devise strategies to provide guidance for clinical interventions and to assist in the design of stents and grafts. Initially, detailed statistical analysis is applied to a three dimensional parametric computer aided design (CAD) model of the human carotid bifurcation. A Bayesian surrogate modelling technique is proposed and discrete locations in the CAD model are taken as random parameters to form inputs for the surrogate model. A metric, maximal wall shear stress (MWSS) is used as an output for constructing the surrogate model and key geometric parameters which influence MWSS are identified by performing three dimensional steady state simulations on the candidate geometries. The ability of the surrogate model to predict arterial geometries which have minimum and maximum MWSS is also discussed. Using these geometries, techniques are proposed for evaluating the degree of severity with respect to the metric MWSS for any patient. Subsequently, a new metric, the integral of negative mean shear stress (INMSS) is used as an output for constructing a new surrogate model and three dimensional pulsatile simulations are performed on the candidate geometries. An optimisation problem is solved to find out the arterial geometries which have minimum and maximum values of INMSS. Due to the computational expense of performing three dimensional pulsatile studies, further parametric analyses are applied to the design of stents and bypass grafts using a one dimensional model capable of simulating fluid-wall interactions. Subsequently, a cost-effective diagnostic technique is proposed for identifying patients with carotid stenosis who could most benefit from angioplasty followed by stenting. For this purpose, pressure variation factor (PVF) and maximum pressure (pm) are used as metrics to rank the performance of each case. Finally, the Bayesian surrogate modelling technique is used to predict optimal bypass graft configurations which have minimal values of PVF.
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Rowe, Christopher Stuart. "Improving the local haemodynamics of bypass graft anastomoses." Thesis, University of Liverpool, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367237.
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Patel, Priya. "Investigation of vasomotion oscillations in spontaneous cortical haemodynamics." Thesis, University of Sheffield, 2016. http://etheses.whiterose.ac.uk/16457/.
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Daly, Jonathan. "Video camera monitoring to detect changes in haemodynamics." Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:e84f2acf-f35c-4257-a4c3-209c5da9cbee.
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Patients in hospital can be prone to sudden, life-threatening changes in their cardiovascular state. Haemodynamic parameters such as blood pressure, pulse transit time (PTT) and perfusion can be monitored in clinical situations to identify these changes as early as possible. Continuous blood pressure is usually monitored using a catheter placed into a major artery, but this is invasive and involves risk to the patient. In the last decade, the field of non-contact vital sign monitoring has emerged, with growing evidence that the remote photoplethysmogram (rPPG) signal can be used to estimate vital signs using video cameras. If the analysis of the rPPG signal can be expanded to include the estimation of haemodynamic parameters, it could result in methods for the continuous, non-contact monitoring of a subject's haemodynamic state. In a physiology study, a series of video recordings were made of 43 healthy volunteers. The subjects sat in a purpose-built chamber, and the composition of the air was carefully adjusted to cause the subjects to experience large, controlled changes in blood oxygen levels. To validate the video camera algorithms, reference data were also collected. Along with the volunteer study, a clinical study was performed to acquire data in a challenging clinical environment. Data were collected from patients on haemodialysis in the Renal Unit, a population likely to experience sudden changes in haemodynamics. The reference data from the Renal Unit study were analysed to determine the extent to which PTT and mean arterial pressure (MAP) are related. The correlation coefficients and linear fits were found on a global and a per-subject basis. In addition, the video recordings from the Physiology study were processed to derive rPPG signals, and these signals were analysed to obtain estimates for PTT. Local rPPG signals were also derived for different regions of interest, and the waveforms were analysed using a novel application of the technique of signal averaging to produce spatial maps of perfusion and blood flow. The correlation between conventionally measured PTT and MAP was found to be weaker in the haemodialysis population than has been shown elsewhere in the literature, except for a sub-set of patients. The results of the video analysis showed that PTT could be estimated robustly and consistently, although direct validation of these estimates was not possible because of the different method used to calculate the reference PTT. For most subjects, the spatial mapping methods produced robust maps that were consistent over time. These results suggest that it is possible to detect changes in haemodynamics using a video camera, and that this could have applications in healthcare, providing that challenges such as subject movement and clinical validation can be overcome.
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Imray, Christopher H. E. "Cerebral haemodynamics in man : clinical and applied observations." Thesis, University of South Wales, 2005. https://pure.southwales.ac.uk/en/studentthesis/cerebral-haemodynamics-in-man-clinical-and-applied-observations(d355a956-a4e5-4fc3-b5ec-35e843c63402).html.
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This overview reviews seventeen publications between 1995 and 2005. CHE Imray was the first author of eleven of the papers, the senior author of four and a major contributor to two of the publications. The overview should be read in conjunction with the full copies of the seventeen publications (Appendix 2). The brain is exquisitely sensitive to oxygen requiring a constant supply of adequately oxygenated blood to function normally. Cerebral oxygen delivery is dynamic, and alters rapidly in response to changes in physiological and pathological stimuli. Interference with cerebral oxygen delivery, either as a result of decreased cerebral blood flow, decreased arterial oxygenation or particulate matter (cerebral microemboli) within the blood can all rapidly result in temporary or permanent loss of function within minutes. The author has used non-invasive cerebral perfusion imaging techniques, initially in the clinical setting (in clinic, at the bedside and in the operating theatre) and later transferring these methods to the field setting at high altitude. As a result of these studies, new insights into cerebral perfusion have been gained. Novel concepts such as 'virtual altitude' and 'partitioning of arterial and venous volumes' have been developed. New equipment has been designed and developed, such as the recumbent, collapsible, portable exercise bike. Finally new clinical treatments have been developed, including an apparently safe way to treat the high-risk group of patients with crescendo transient ischaemic attacks or mini-strokes, greatly reducing the risk of developing a subsequent major stroke. The work submitted for consideration for a PhD by publication represents ten years of investigation in two closely inter-related fields. The aim of the submission is to provide a background to the seventeen publications (Appendix 2) allowing them to be seen in context to existing knowledge. Appendix 3 contains twelve additional communications that have either been published, or accepted for publication after the original list of seventeen publications was submitted to the University of Glamorgan. They confirm the author's ongoing interest and contributions to this field of research.
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Davies, Justin Edgar Rees. "Coronary haemodynamics in hypertension and left ventricular hypertrophy." Thesis, Imperial College London, 2011. http://hdl.handle.net/10044/1/7793.
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The coronary blood flow waveform is unique, being determined by simultaneous changes in pressure originating at either end of the coronary artery. However, by measuring the coronary pressure waveform alone, it is not possible to separate the pressure contributions originating from the coronary microcirculation from those originating in the aorta. In this thesis wave intensity analysis was applied to unobstructed human coronary arteries to separate the contributions originating in the coronary microcirculation from those originating in the aorta, in subjects with and without left ventricular hypertrophy. I found that coronary blood flow is predominantly regulated by changes in microcirculatory-originating pressure, and not be aortic-originating pressure as is the case in other vascular beds. I identified six waves which were responsible for directing these changes in pressure. Coronary blood flow peaks during diastole due to a dominant backward-travelling 'suction' wave, generated when microcirculatory compression is relieved and pressure in the distal artery falls rapidly. This backward-travelling 'suction' wave was found to be significantly reduced in subjects with left ventricular hypertrophy. Finally, wave intensity was applied in the proximal aorta to assess the contribution of distal reflections to coronary blood flow. Wave reflections could be seen travelling back from the proximal aorta into the coronary arteries. These reflections augment coronary blood flow during systole and are more marked in older subjects.
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Insall, R. L. "Pulse waveforms and transit time from photoelectric plethysmography in the diagnosis of peripheral vascular disease." Thesis, University of Newcastle Upon Tyne, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.309069.
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Piechnik, Stefan K. "A mathematical and biophysical modelling of cerebral blood flow and cerebrospinal fluid dynamics." Thesis, University of Cambridge, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.269226.
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De, Villiers Anna Magdalena. "A patient-specific FSI model for vascular access in haemodialysis." Doctoral thesis, University of Cape Town, 2017. http://hdl.handle.net/11427/24441.
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This research forms part of an interdisciplinary project that aims to improve the understanding of haemodynamics and vascular mechanics in arteriovenous shunting. To achieve the high flow rates that enable patients with renal disease to receive haemodialysis, a fistula is created between an artery and a vein. The patency rate of fistulas, especially those located in the upper arm, is low. The approach adopted here makes use of new magnetic resonance image (MRI) technology and computational modelling of blood flow, with a view to improving therapeutic strategies of disease requiring vascular interventions. This thesis presents the construction and development of a 3D finite element model of the fluid-structure interaction in a brachial–cephalic patient–specific fistula. An overview of the mathematical models that describe the vessel wall and fluid behaviour as well their interaction with each other is given. An Arbitrary Lagrangian- Eulerian (ALE) framework is used together with a transversely isotropic hyperelastic constitutive model for the vessel walls, while blood flow is modelled as a Newtonian fluid. A three-element Windkessel model is used to allow the fluid to move through the outlets of the computational domain without causing non–physical reflections. Flow data acquired from MRI is used to prescribe the flow at the inlet. The parameters of the Windkessel-model at the two outlets are calibrated to resemble the flow acquired from the 2D MRI. The model is validated against the flow patterns acquired from the 4D MRI. The flow patterns of the blood, and stress present in the vessel are investigated. Of special significance are the flow and wall shear stress at the anastomosis. An area of very high velocity in the anastomosis is followed by an area of recirculation and low velocity. The propagation of pressure waves and their reflection at the anastomosis are studied. Areas that are subjected to low wall shear stress, high oscillatory wall shear stress or flow circulation are identified as areas where intimal hyperplasia may develop. The flow results from the simulation show good qualitative agreement with the MRI data.
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Frazer, Katherine H. "Computational estimation of haemodynamics and tissue stresses in abdominal." Thesis, University of Edinburgh, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.491581.
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Whinnett, Zachary Ian. "Optimisation of cardiac resynchronisation therapy using non-invasive haemodynamics." Thesis, Imperial College London, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.542962.
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Daub, Anna Christina [Verfasser]. "Numerical Haemodynamics in the Human Heart / Anna Christina Daub." Karlsruhe : KIT Scientific Publishing, 2018. http://www.ksp.kit.edu.
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Boldock, Luke. "The influence of stent geometry on haemodynamics and endothelialisation." Thesis, University of Sheffield, 2017. http://etheses.whiterose.ac.uk/19272/.
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Every year, millions of people worldwide undergo stent implantation to widen narrowed arteries or to redirect blood away from aneurysms. The rapid post-operative regrowth of a healthy endothelial layer, a key factor in stented artery repair, would reduce complications and improve quality of life for many patients. While this has long been a clinical or pharmaceutical issue, this project considers the role of local haemodynamics, specifically the effects of stent-modified wall shear stress on the endothelium. Endothelial cells have a strong mechanobiological response to wall shear stress magnitude, direction and time variance. To understand the impact of stent geometry on this response through altered fluid dynamics, a novel model vessel was developed for the deployment of a wide range of coronary and flow diverter stents in vitro. The model allowed the observation of both endothelial cell migration and, via particle tracking, disturbed flow within the stents. High-resolution micro-computed tomography scanning techniques replicated stent geometry in silico, enabling computational fluid dynamics simulations for the assessment of wall shear stress distribution. Coronary stents greatly influenced fluid flow. The orientation and distribution of tracked particle streamlines were transformed proximal to stents struts, which were also areas of reduced wall shear stress. These areas correlated with zones of reduced cell migration. Flow diverter stents had a lesser impact on observable particle flow; yet endothelial cell migration within them was completely arrested. This is likely due to their structure directing flow away from the wall and reducing shear stress to an even greater extent that coronary stents, over a more substantial area. Dissimilar cell migration between coronary and flow diverter stents is a point of possible significance as the two are treated alike with respect to post-operative care and medication. Continued analysis of various geometries may enable the efficacy of individual stent designs to be quantified or predicted. By applying this knowledge in the future, careful stent design could reduce their impact, or exert an intentional, active influence on endothelial cells, to optimise the healing process.
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Quail, M. A. "Comprehensive assessment of vascular haemodynamics by magnetic resonance imaging." Thesis, University College London (University of London), 2016. http://discovery.ucl.ac.uk/1482118/.
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Haemodynamics is concerned with the physiological and mechanical factors that determine pressure and flow in the circulation. Currently no diagnostic modality in clinical practice provides simultaneous pressure and flow data, and therefore our analysis of fundamental haemodynamic problems is limited. Cardiac catheterisation with conventional technology can measure pressure as a function of time but can only provide estimates of mean flow. In contrast cardiac magnetic resonance imaging (CMR) can measure flow as a function of time, but cannot directly measure pressure. It is desirable that both pressure and flow signals be acquired and integrated using non-invasive techniques to measure fundamental haemodynamic components. In this thesis it is proposed to develop methods for comprehensive haemodynamic assessment using non-invasive CMR data. The cross-sectional area of a vessel is related to its intra-luminal pressure. The first experiment of this thesis tested the hypothesis that central aortic systolic blood pressure (c-SBP) could be derived from the time-varying cross-sectional area of the ascending aorta, using models of the pressure area relationship. The method was validated using carotid tonometry as a surrogate of central aortic pressure in 20 volunteers. The second experiment tested the hypothesis that the principle components of central haemodynamics: systemic vascular resistance, central compliance, characteristic impedance and wave reflections could be measured non-invasively. The study utilised the previously developed techniques in a study of 50 patients with repaired coarctation of the aorta and 25 healthy controls. Pressure, area and flow data were further integrated to assess wave reflections in the aorta using a technique called wave intensity analysis. Using these methods it was demonstrated that patients with repaired coarctation have elevated c-SBP despite similar peripheral SBP to controls. Furthermore patients have increased vascular stiffness and abnormal wave reflections. These parameters were found to be important determinants of elevated LV mass in this population, and were superior to conventional biomarkers such as coarctation index and peripheral-SBP. The final experiment tested the hypothesis that wave reflections could be assessed in the pulmonary circulation. 20 patients with pulmonary hypertension and 10 controls were recruited. It was hypothesized that wave intensity analysis could detect differences in reflections in PH patients compared to healthy controls and could also differentiate certain PH subtypes. This experiment showed that the presence of a backwards compression wave, reflected from the lungs, identified patients with PH and its magnitude showed discriminatory capacity for the presence of proximal PA clot in patients with Chronic Thromboembolic Pulmonary Hypertension (CTEPH).
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Kirkham, Fenella Jane. "Cerebral haemodynamics in normal subjects and children in coma." Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.611486.
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Broyd, Christopher. "Coronary haemodynamics and wave intensity analysis in aortic stenosis." Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/23961.
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Introduction: Coronary Wave Intensity Analysis (WIA) provides an invasive measure of energy transfer within the coronary circulation. I set out to derive a non-invasive measure of the backward expansion wave (BEW) responsible for coronary flow and assess it during exercise and in aortic stenosis (AS). Methods: 17 patients (mean age 60, 11 male) with normal cardiac function underwent invasive LAD WIA calculation using a pressure- and flow-tipped wire. Non-invasive WIA was calculated immediately after angiography from simultaneous PW Doppler of the LAD and a suprasystolic-cuff derived measure of central pressure. Non-invasive WIA was then assessed in 9 healthy volunteers whilst exercising on an exercise bike, 25 patients with varying degrees of AS (AVmax range: 2.41-5.43m/s) and 29 patients before, after and at 6 and 12 months following aortic valve intervention for severe AS. Results: Mean peak BEW was -14.7 ± 8.7x104 Wm-2s-2 invasively and -14.4 ± 8.2 Wm-2s-2 non-invasively and increased with exercise (at peak: -20.5±6.8Wm-2s-2, p=0.02) along with a rise in coronary flow (28.8cm/s to 42.1cm/s, p 0.06). A significant correlation was noted with the BEW and AS severity, strongest when valvulo-arterial impedence was assessed (r=-0.66, p<0.001). In severe AS, a reduction in coronary flow (0.41 to 0.33m/s, p<0.01) and the BEW (-22.1 vs 10.9x104Wm-2s-2, p<0.01) was seen after intervention. With LVH regression BEW increased (-21.6±12.6x104 Wm-2s-2 at 6 months) without a significant change in coronary flow. Conclusion: It is possible to construct a non-invasive measure of coronary WIA thus markedly increasing its applicability. Using this technique, the BEW is seen to increase during progressive levels of exercise accounting for the increase in coronary flow. The BEW progressively climbs with increasing AS, falls to sub-normal levels after aortic valve intervention but then increases to normal levels with LVH regression.
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Zhang, Kai. "Regional tissue oxygenation and haemodynamics interrogation using NIR light." Thesis, Keele University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261529.
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Cremona, George Ian. "Nitric oxide and pulmonary vascular resistance in health and disease." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360748.
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Wilson, Paul. "Computational fluid dynamic investigation of blood flow through heart valve prostheses." Thesis, Nottingham Trent University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360773.
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Waller, John. "Cardiovascular regulatory mechanisms in endotoxaemia." Thesis, University of Nottingham, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.307806.
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Mackin, Paul. "The effects of angiotensin-converting enzyme inhibition on glomerular morphology in acute experimental diabetes." Thesis, University of Newcastle Upon Tyne, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262885.
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Wesołowski, Roman. "Development of arterial spin labelling methods for monitoring cerebral haemodynamics." Thesis, University of Nottingham, 2010. http://eprints.nottingham.ac.uk/13854/.
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The work described in this thesis was carried out at the Sir Peter Mansfield Magnetic Resonance Centre at the University of Nottingham between March 2006 and December 2009. All work described in this thesis was performed by the author, except where indicated. This thesis aims to develop and implement ASL techniques to measure haemodynamic responses to neural activity. The development of a new technique Double Acquisition Background Suppression (DABS) is presented as a remedy for a newly discovered artefact affecting Philips Achieva 7 T scanners and other sources of variation in baseline signals such as physiological noise. The new technique (DABS) was developed for simultaneous acquisition of ASL (with suppressed static tissue signal) and BOLD data using the FAIR scheme. This method not only provided a solution to obtaining ASL data at 7 T, despite the Roman Artefact, but also proved to reduce the contribution of physiological noise to ASL images, which is problematic, especially at ultra-high magnetic field strengths. The statistical verification was carried out based on the neural activation induced by a finger-tapping stimulus. A simplified model for quantifying CBVa.with the Look-Locker sampling method is proposed in this thesis to overcome the need for the Step-wise Compartmental Model (SCM). The Look-Locker sampling scheme acquires multiple readout pulses following the labelling and provides an estimation of transit time as well as CBVa. Here the simplified model is used to assess changes due to visual stimulation and validated against the SCM model. The application of LL-FAIR to form CBF and CBVa weighted data with improved SNR compared to traditional single TI FAIR technique is then shown. This method uses a summation over LL-EPI readout pulses and is used to asses the temporal characteristics and absolute changes in CBF and CBVa haemodynamic responses to a short (4.8 s) and long (9.6 s) visual stimulus. LL-FAIR methods are then used to appraise the neural coupling of haemodynamic parameters and assess Grubb's relationship. CBF and CBVa. Data were collected together with CBVtot data from a bolus injection of contrast agent. Assessing Grubb's power-law (CBVtot = CBFCI:)for neuronal activation, which was originally derived in primates during a steady state response of hypercapnia, a was found in this human study to be between 0.22 ± 0.08 and 0.29, dependent on the analysis method. In addition, the power-law relationship between CBVtot and CBVa.was assessed, and resulted in a similar relation, yielding aTA = 0.42 ± 0.14 and 0.40. Since CBF is thought to be driven by CBVa.the power-law between these parameters was also tested with a value of aFA = 1.35 ± 0.64 and 1.21, found in close agreement with earlier animal work.
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Hadjiloizou, Nearchos. "The effect of regional ventricular dysfunction on coronary artery haemodynamics." Thesis, Imperial College London, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.516134.
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Ariff, Ben B. "Computational modelling of carotid artery haemodynamics in relation to atherosclerosis." Thesis, Imperial College London, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.520969.
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Yang, Wenxuan. "A pharmacological study of hepatic haemodynamics during secondary biliary cirrhosis." Thesis, King's College London (University of London), 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.405249.
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McElroy, Michael. "Boundary condition assessment and geometrical accuracy enhancement for computational haemodynamics." Thesis, Manchester Metropolitan University, 2017. http://e-space.mmu.ac.uk/619019/.
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Cardiovascular diseases cause over 47 % of all deaths in Europe each year. Computational fluid dynamics provides the research community with a unique opportunity to investigate cardiovascular diseases with the intent of enabling optimised, patient-specific medical therapies. Incorporating physiologically accurate geometries and boundary conditions into computational fluid dynamics simulations can be difficult tasks and are a concern for researchers. This thesis analyses the impact various inlet and outlet boundary conditions can have on the outcome of a simulation. It also presents a novel, semi-automated process that prepares accurate geometrical models for haemodynamic simulations. Firstly, rabbit and human aorta models were used to analyse the impacts of boundary conditions on haemodynamic metrics used for understanding cardiovascular disease pathology. Comparisons were made between traction free, Murray’s Law, three-element Windkessel, and Murray’s Law/in vivo data hybrid outlet boundary conditions. Steady-state, transient, fully-developed and plug-type inlet boundary conditions were also investigated. Results showed that when advanced models such as the three-element Windkessel are unavailable, the Murray’s Law based outlet returns the most physiologically accurate haemodynamics. Results also showed that prescribing a transient simulation and a fully-developed flow at the inlet are not required when the focus is only on the flow within the aorta and around the intercostal branches. Secondly, a sensitivity test was conducted on the simulation of Left Ventricular Assistive Device (LVAD) configurations. The effects of flow ratios between the LVAD and aortic root on haemodynamic metrics were quantified. The general irregular sensitivity of the subclavian and carotid arteries to flow ratios indicates that the perfusion and wall shear stress-based haemodynamic metrics within these arteries cannot be accurately predicted unless the flow ratios are incorporated into the preoperative planning of the optimal LVAD configuration. Finally, a semi-automated reconstruction process combining magnetic resonance angiography and optical coherence tomography data was developed. The process was successful in its ability to create an accurate geometry in a relatively short time. This forms the foundation on which more sophisticated methods can be developed.
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Sivanesan, Sharmila. "Correlating geometry, haemodynamics and intimal hyperplasia in radiocephalic arteriovenous fistulae." Thesis, University of Liverpool, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337127.
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Fryer, Simon. "Physiological and psychological contributions to on-sight rock climbing, and the haemodynamic responses to sustained and intermittent contractions." Thesis, University of Canterbury. School of Sport and Physical Education, 2013. http://hdl.handle.net/10092/8704.
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Rock climbing is a multi-dimensional sport encompassing physiological, psychological, bio-mechanical and skill components. Interpretation of data in current investigations is limited by the lack of knowledge regarding the extent of the potential interaction of pre-climb anxieties with the physiological responses during an ascent. This thesis attempts to delineate the psychological and physiological contributions of on-sight top rope and lead climbing in multiple ability groups of rock climbers. Furthermore, the thesis goes on to gain an understanding of the de-oxygenation and re-oxygenation profiles in two forearm flexors during sustained and intermittent contractions-to-failure, as well as during the subsequent recovery period.
In study one, intermediate, advanced and elite rock climbers were asked to on-sight a route at the top of their respective best self-reported on-sight grade. There were no ability group or ascent style differences for any pre-climb measures of anxiety. However, elite rock climbers had significantly higher oxygen consumption, heart rate (HR) and cortisol (physiological component) responses compared to lower ability groups. Furthermore, the elite climbers spent a significantly greater percentage of their static time resting during the ascent compared to all lower ability groups. As there appears to be no differences in the anxiety based interaction with the physiological response, study one suggests that ability group and ascent style differences may be attributed mainly to the changes in the physical demands of the route. Furthermore, it would appear the higher level rock climbers may have a greater reliance on the aerobic metabolism during an on-sight ascent.
Study two investigated the haemodynamic responses to sustained and intermittent handgrip contractions which are seen during rock climbing ascents. Intermediate, advanced and elite climbers as well as a control group were asked to perform sustained and intermittent contractions (10s) at 40% of maximal volitional capacity until exhaustion. Oxygen saturation, blood flow (BF) and HR were measured pre, during and post contractions. Elite and advanced climbers were able to de-oxygenate both the flexor digitorum profundus and the flexor carpi radialis significantly more than the intermediate climbers, and the control group. During the intermittent test to failure, relative re-oxygenation during the rest period (3s) (re-oxygenation which takes into account the amount of de-oxygenation during the previous contraction), may be an important determinant of the force time integral. During the intermittent test, the increase in Δ BF, release HR and Δ HR during the rest periods suggest that vessel occlusion in elite and advanced rock climbers may not be as prominant as previously speculated upon. Furthermore, elite rock climbers appear to have a significantly faster time to half recovery after both sustained and intermittent contractions-to-failure.
In conclusion, it would appear that the psychological responses assessed pre on-sight rock climbing may not be different between ability groups or ascent styles. Instead, ability group differences may be due to physiological adaptations caused in part by the significantly greater amount of training. Furthermore, elite rock climbers appear to be able to de-oxygenate and re-oxygenate faster and to a greater extent than lower ability level climbers due to an increased Δ BF and Δ HR during intermittent rest periods, as well as post-exercise. Further investigation focusing on aerobic/anaerobic contribution, determination of capillary density and muscle fiber type would aid in gaining a greater understanding of rock climbing performance.
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Cole, Jonathan Samuel. "Pulsatile, non-Newtonian blood flows through typical arterial bypass graft models." Thesis, Queen's University Belfast, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326405.
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Thomas, Nicholas. "On the application of the Doppler effect in pulsed Doppler flowmeters and the effect of certain propagation and scattering artifacts." Thesis, King's College London (University of London), 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297092.
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Yu, Wai-yin Alex. "Haemodynamics in dialysis hypotension and the possible role of splanchnic circulation." Click to view the E-thesis via HKUTO, 2006. http://sunzi.lib.hku.hk/hkuto/record/B36364162.
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Jackson, Mark John Clinical School St Vincent's Hospital Faculty of Medicine UNSW. "A study of vein graft haemodynamics using computational fluid dynamics techniques." Awarded by:University of New South Wales, 2007. http://handle.unsw.edu.au/1959.4/38575.
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Atherosclerosis, the leading cause of mortality in Western societies, affects large elastic arteries, causing focal deposition of proliferative inflammatory and lipid-laden cells within the artery. Several risk factors have been causally implicated in the ???reaction to injury??? hypothesis first described by Ross in 1969. The ???injury??? sustained by endothelial cells may be either mechanical or chemical. Environmental factors have a role in the production of chemical agents that are injurious to the endothelium. Mechanical stresses such as wall tensile stress are proportional to systemic blood pressure and pulse pressure. Essentially, these systemic pressures are fairly evenly distributed throughout the circulation. However, atherosclerotic lesions characteristically occur at focal sites within the human vasculature; at or near bifurcations, within the ostia of branch arteries and at regions of marked or complex curvature, where local haemodynamic abnormalities occur. The most discussed haemodynamic factor seems to be low or highly oscillating wall shear stress which exists on the outer wall of bifurcations and on the inner aspect of curving vessels. The magnitude of these haemodynamic forces may not be great but the subtleties of their variable spatial distribution may help to explain the multifocal distribution of atherosclerotic plaques. With the altered haemodynamics there is endothelial injury and phenotypic changes in the endothelium result, which in turn lead to endothelial cell dysfunction. These haemodynamic variables are difficult to measure directly in vivo. In this work a novel model is developed utilising human autologous vein bypass grafts as a surrogate vessel for the observation of pathological structural changes in response to altered haemodynamics. The influence of haemodynamic factors (such as wall shear stress) in the remodeling of the vein graft wall and the pathogenesis of Myointimal Hyperplasia (MIH) and resultant wall thickening in femoral bypass grafts is analysed. The haemodynamic determinants of MIH (which have been established in many animal models) are similar to those implicated in atherosclerosis. The accelerated responses of the vein (Intimal hyperplasia develops much more rapidly than atherosclerotic lesions in native vessels) make it an ideal model to expediently examine the hypothesised relationships prospectively in an in vivo setting. Furthermore, the utilisation of in vivo data acquired from non-invasive diagnostic methods (such as Magnetic Resonance Angiography (MRA) and Duplex ultrasound) combined with the application of state-of-the-art Computational Fluid Dynamic (CFD) techniques makes the model essentially non-invasive. The following hypotheses are examined: 1) regions of Low shear and High tensile stress should develop disproportionately greater wall thickening, 2) regions of greater oscillatory blood flow should develop greater wall thickening, and 3) regions of lower wall shear should undergo inward (or negative) remodelling and result in a reduction in vessel calibre. The conclusions reached are that abnormal haemodynamic forces, namely low Time-averaged Wall Shear Stress, are associated with subsequent wall thickening. These positive findings have great relevance to the understanding of vein graft MIH and atherosclerosis. It was also evident that with non-invasive data and CFD techniques, some of the important haemodynamic factors are realistically quantifiable (albeit indirectly). The detection of parameters known to be causal in the development of graft intimal hyperplasia or other vascular pathology may improve ability to predict clinical problems. From a surgical perspective this might be employed to facilitate selection of at-risk grafts for more focused postoperative surveillance and reintervention. On a broader stage the utilisation of such analyses may be useful in predicting individuals at greater risk of developing atherosclerotic deposits, disease progression, and the likelihood of clinical events such as heart attack, stroke and threat of limb loss.
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Beattie, David Keith. "The influence of altered haemodynamics on human smooth muscle cell behaviour." Thesis, Imperial College London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369122.
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Ngoepe, Malebogo N. "Computational modelling of thrombotic processes and complex haemodynamics in cerebral aneurysms." Thesis, University of Oxford, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.639454.
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A clot in a cerebral aneurysm can either accelerate the road to rupture, through inflammatory processes and furthering vascular wall degradation, or stabilise the situation by occluding the aneurysm, and thus prevent rupture. A three-dimensional computational model of clotting in patient-derived cerebral aneurysm geometries is presented. The model accounts for the biochemical reactions that make up the clotting process, for realistic three-dimensional haemodynamics in image-derived vasculature representations and for the growing clot's interaction with and impact on the flow field. The flow is accounted for by the Navier Stokes equations and the transport equation describes the changes in biochemical species concentrations. Level Set methods are used to track the surface of the growing clot in the three-dimensional geometries studied. The influence of the thrombosed region on the haemodynamics is accounted for by modifying the local porosity and permeability, to reflect the fibrous and permeable nature of the clot. The model is first developed, examined and parameterised for a physiological model of clotting in two dimensions and is then extended and demonstrated for the pathological case in three dimensions
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Yu, Wai-yin Alex, and 余惠賢. "Haemodynamics in dialysis hypotension and the possible role of splanchnic circulation." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2006. http://hub.hku.hk/bib/B36364162.
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Fraser, Katharine H. "Computational estimation of haemodynamics and tissue stresses in abdominal aortic aneurysms." Thesis, University of Edinburgh, 2007. http://hdl.handle.net/1842/24588.
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Abdominal aortic aneurysm is a vascular disease involving a focal dilation of the aorta. The exact cause is unknown but possibilities include infection and weakening of the connective tissue. Risk factors include a history of atherosclerosis, current smoking and a close relative with the disease. Although abdominal aortic aneurysm can affect anyone, it is most often seen in older men, and may be present in up to 5.9% of the population aged 80 years. Biomechanical factors such as tissue stresses and shear stresses have been shown to play a part in aneurysm progression, although the specific mechanisms are still to be determined. The growth rate of the abdominal aortic aneurysm has been found to correlate with the peak stress in the aneurysm wall and the blood flow is thought to influence disease development. In order to resolve the connections between biology and biomechanics, accurate estimations of the forces involved are required. The first part of this thesis assesses the use of computational fluid dynamics for modelling haemodynamics in abdominal aortic aneurysms. Boundary conditions from the literature on healthy patients are used, along with patient specific aneurysm geometries, to obtain a first estimate of blood flow patterns and haemodynamic wall parameters within the aneurysms. The use of healthy patient boundary conditions is difficult to justify as the presence of the aneurysm is likely to alter the flow rate in the aorta. This is investigated with a Doppler ultrasound study of blood velocities in the normal and aneurysmal aorta. Archetypal waveforms reveal a significant difference in the diastolic maximum of young healthy volunteers and AAA patients. The archetypal aortic velocity wave for patients with abdominal aortic aneurysm is used to calculate the haemodynamics in a group of patients and these calculations are compared with those obtained using patient specific boundary conditions, and with phase-contrast magnetic resonance imaging measurements of blood velocity. With the correct z-velocity profile at the entrance to a short inlet section proximal to the aneurysm, the calculated velocities agreed qualitatively with the measured velocities. However, the velocities calculated using the correct inlet flow rate, but a simple velocity profile, are quite different from the measurements. These results show that the correct velocity profile at the aneurysm entrance is required to predict velocities within the aneurysm cavity. In reality the blood and the artery wall interact: the blood flow domain continually dilates and contracts, altering the flow patterns; the flow controls the pressure on the wall and therefore the stresses within it. The influence of this fluid-structure interaction on the blood flow and tissue stresses is investigated in axially symmetric models of abdominal aortic aneurysm. Modelling of the complete fluid-structure interaction reveals how the pressure and flow waves are distorted by the aneurysm geometry. This distortion, which is absent from both static pressure and one way coupled models, accounts for the small errors in tissue and wall shear stresses obtained when using these models with lower computational complexity. These errors vary with the type of modelling as well as the aneurysm diameter and elasticity. A one dimensional, lumped parameter model of the aneurysm is developed to elucidate the effect of aneurysm geometry on the propagation of pressure and flow waves. It reveals interesting consequences of the diameter of the aneurysm on its inductance and resistance, and its use in improving the outlet pressure boundary condition is investigated.
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Pang, Kar Lai. "The role of abnormal haemodynamics and cardiac troponin T in cardiogenesis." Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/39193/.
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The heart is the first functioning organ to develop during embryogenesis to maintain the growing embryo with oxygen and nutrients. However, cardiogenesis is a complex and highly coordinated biological process, and any perturbation to this process can result in detrimental defects to the heart. Haemodynamics is known to play an important role in cardiac growth and vasculature remodelling. Congenital heart defects (CHDs) accounts for 0.4-1.3% of all live birth, whereas cardiomyopathy accounts for 8-11% of cardiovascular disease diagnoses detected in utero. Although the heart defects and cardiomyopathies are known to be attributed by genetic mutations, most cases have unknown etiology. Hence, OFT-banding model was employed to alter the haemodynamic loading via pressure overloading. Upon alteration of haemodynamics, enlargement of the heart with a spectrum of cardiac anomalies were found (e.g ventricular septal defects, thickened epicardium and dysmorphic atrioventricular valves) upon morphological and stereological analysis. A study of global differential expression of OFT-banded hearts by RNA sequencing revealed a number of differentially expressed genes and they were associated with cardioprotection, metabolism, shear stress and valve development; further, a reduction of apoptosis was seen in these banded hearts as well. One of the cardiac phenotypes seen upon OFT-banding, the abnormal primordial atrioventricular valve, was further characterized to provide an insight how the atrioventricular valve is affected upon alteration of haemodynamics. Aberrant expressions of extracellular matrix (ECM) genes such as TBX20, Aggrecan and Periostin alongside with the shear stress responsive genes (KLF2 and EDN1) were found, and a decrease in apoptosis was seen. Moreover, dysregulation of ECM proteins such as fibrillin-2, type III collagen and tenascin were further demonstrated in more mature primordial AV leaflets at HH35, with a concomitant decrease of ECM cross-linking enzyme, transglutaminase-2. In addition, for many years sarcomeric proteins have been associated with a range of cardiomyopathies, but only in recent years they have been linked to congenital heart defects (CHDs). To date, cardiac troponin T (TNNT2) has been associated with cardiomyopathies but not with isolated CHDs. TNNT2 encodes for cTnT regulatory proteins of the thin filament of the sarcomere and is vital for muscle contraction and force generation within cardiomyocytes. To investigate a role of TNNT2 in the early developing heart, targeted manipulation of TNNT2 was performed in embryonic chick to reduce the protein levels of cTNT (protein product of TNNT2) in ovo via translational block. Abnormal atrial septal growth, reduced ventricular trabeculation and ventricular diverticula were found upon TNNT2 morpholino treatment. The abnormal phenotype observed in the TNNT2 morpholino-treated groups was potentially suggested by differential expression of shear stress responsive gene, NOS3 gene.
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Griffiths, Matthew R. "Dynamic contrast-enhanced CT in the investigation of tumour angiogenesis and haemodynamics." Thesis, Queensland University of Technology, 2008. https://eprints.qut.edu.au/16679/1/Matthew_Roland_Griffiths.pdf.
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This manuscript presents an investigation and application of the medical radiographic technique of Dynamic Contrast-enhanced Computed Tomography with an emphasis on its application to the measurement of tissue perfusion using the techniques of CT Perfusion. CT Perfusion was used in association with Fluoro- Deoxy Glucose Positron Emission Tomography (FDG PET) to investigate altered blood flow due to the angiogenic effects of tumour in the clinical setting of medical imaging for cancer diagnosis and staging.
CT perfusion, CT enhancement and Doppler ultrasound studies were compared in a series of patient studies performed for the assessment of metastatic liver disease. There was good correlation between all techniques for the arterial phase but not between Doppler measurements of the portal phase and any CT measurement. A new method was developed for quantifying CT perfusion and enhancement values, the Standardised Perfusion Value (SPV) and the Standardised Enhancement Value (SEV). The SPV was shown to correlate with FDG uptake in a series of 16 patient studies of lung nodules, an unexpected and potentially important finding that if confirmed in a larger study may provide an additional diagnostic role for CT in the assessment of lung nodules.
Investigation of a commercially available package for the determination of CT Perfusion, CT Perfusion GE Medical Systems, was undertaken in a small series of brain studies for assessment of acute stroke. This data set showed the technique to positively identify patients with non-hemorrhagic stroke in the presence of a normal conventional CT, to select those cases where thrombolysis is appropriate, and to provide an indication for prognosis.
An investigation of the accuracy and cost-effectiveness of FDG PET in solitary pulmonary nodules using Australian data was carried out. FDG PET was found to be accurate, cost saving and cost effective for the characterisation of indeterminate solitary pulmonary nodules in Australia. This work was expanded to include the impact of quantitative contrast enhancement CT (QECT) on the cost-effectiveness of FDG PET. The addition of QECT is a cost effective approach, however whether QECT is used alone or in combination with FDG PET will depend on local availability of PET, the cost of PET with respect to surgery and the prior probability of malignancy.
A published review of CT perfusion, clinical applications and techniques, is included in the body of the work.
Dynamic contrast-enhanced CT and FDG PET were used to investigate blood flow, expressed as SPV, and metabolic relationships in non-small cell lung cancers (NSCLC) of varying size and stage. A significant correlation between SPV and FDG uptake was only found for tumours smaller than 4.5 cm2. Blood flow-metabolic relationships are not consistent in NSCLC but depend on tumour size and stage. Dynamic contrast-enhanced CT as an adjunct to an FDG study undertaken using integrated PET-CT offers an efficient way to augment the assessment of tumour biology with possible future application as part of clinical care. In summary the work has developed a method for standardizing the results of dynamic contrast-enhanced CT and investigated its potential when applied with FDG PET to improve the diagnosis and staging of cancers.