Kliknij ten link, aby zobaczyć inne rodzaje publikacji na ten temat: Blood Flow Analysis.
Rozprawy doktorskie na temat „Blood Flow Analysis”
Utwórz poprawne odniesienie w stylach APA, MLA, Chicago, Harvard i wielu innych
Sprawdź 50 najlepszych rozpraw doktorskich naukowych na temat „Blood Flow Analysis”.
Przycisk „Dodaj do bibliografii” jest dostępny obok każdej pracy w bibliografii. Użyj go – a my automatycznie utworzymy odniesienie bibliograficzne do wybranej pracy w stylu cytowania, którego potrzebujesz: APA, MLA, Harvard, Chicago, Vancouver itp.
Możesz również pobrać pełny tekst publikacji naukowej w formacie „.pdf” i przeczytać adnotację do pracy online, jeśli odpowiednie parametry są dostępne w metadanych.
Przeglądaj rozprawy doktorskie z różnych dziedzin i twórz odpowiednie bibliografie.
1
Nasimi, Seerous Ghulam Abbas Ali. "Analysis of skin blood flow signals". Thesis, University of Bradford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305700.
Pełny tekst źródła
2
Park, Chang Sub. "Mathematical techniques for the analysis of unsteady blood flow". Thesis, University of Oxford, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.532000.
Pełny tekst źródła
3
Wicks, David Andrew Greenwood. "Intravascular blood flow measurement by quantitative cineangiographic image analysis". Thesis, University of Manchester, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.277411.
Pełny tekst źródła
4
Andrew, Margaret L. "Automatic analysis of gated blood pool studies". Thesis, University of Brighton, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334330.
Pełny tekst źródła
5
Nitzpon, Hans-Jürgen. "Doppler ultrasound analysis of high velocity and turbulent blood flow /". [S.l.] : [s.n.], 1994. http://library.epfl.ch/theses/?nr=1274.
Pełny tekst źródła
6
Davis, Paul H. "Analysis of non-Newtonian effects in separated blood flow regions". Thesis, Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/17912.
Pełny tekst źródła
7
Javan, Roshtkhari Soroor. "Analysis of blood flow during vascular development in chick embryos". Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=104810.
Pełny tekst źródłaStreszczenie:
The cardiovascular system is the first fully functional organ system in the vertebrate embryo. Proper formation of the vasculature is essential for proper embryonic development. Blood flow plays a significant role in the adaptable characteristics of the vessels, as well as innetwork remodelling. As soon as blood flow begins, vessels respond to external stimuli such asshear stress, the tangential force created by the blood flow, which affect the surrounding tissue. Shear stress is the product of both the velocity profile in the vessel and the viscosity of the flowing fluid, and these parameters were determined in vivo. In this research, we have measured changes in the flow velocity, using micro particle image velocimetry (µPIV) at different somite stages during the development of the chick embryo. We measured the viscosity of avian embryonic blood for the first time ever, using a micro viscometer and calculated the change inshear stress during vascular remodelling. We observed that shear stress increases after the onset of blood flow (14 somites), until the stage where large vessels become obvious (25 somites) where a decrease in shear stress is observed. Furthermore, we found that the apparent hematocrit with respect to vessel diameter decreases with decreasing vessel radius, an effect known as the Fahreus-Lindqvist effect. We also found that the embryonic blood viscosity is non-Newtonian and displays shear-thinning behavior, similar to adult blood.Le système cardiovasculaire est le premier organe entièrement fonctionnel chez l'embryon vertébré. Une formation appropriée de la vascularisation est indispensable pour le bon développement embryonnaire. Le flux sanguin a un rôle important autant dans les caractéristiques d'adaptation vasculaire que dans le remodelage. Dès que le flux sanguin commence, les vaisseaux répondent aux stimuli externes tels que les forces de cisaillement (shear stress) et la force tangentielle créée par le flux sanguin, ce qui affecte le tissu environnant. Le shear stress est le résultat du produit de la vitesse dans le vaisseau avec la viscosité du flux, paramètres ayant été déterminés in vivo. Dans cette étude, nous avons mesuré les changements de la vitesse de flux en utilisant la technique de micro particle image velocimetry (µPIV) à différents stades (somites) du développement de l'embryon de poulet. Pour la première fois, nous avons mesuré la viscosité du sang embryonnaire aviaire en utilisant un micro viscomètre et nous avons calculé le changement de shear stress au cours du remodelage vasculaire. Nous rapportonsque les niveaux de shear stress augmentent après le début du flux sanguin (14 somites) jusqu'au stade où de gros vaisseaux deviennent apparents (25 somites), stade auquel nous observons une diminution des niveaux de shear stress. En outre, l'hématocrite relié au diamètre vasculaire, diminue lors d'une réduction du rayon vaculaire, effet connu sous le nom d'effet de Fahreus-Lindqvist. Nous constatons aussi que la viscosité du sang embryonnaire n'est pas newtonienne et démontre un comportement de réduction du shear stress, observation similaire au sang adulte.
8
James, Peter Welbury. "Design and analysis of studies to estimate cerebral blood flow". Thesis, University of Newcastle Upon Tyne, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.251020.
Pełny tekst źródła
9
Xu, Xiong. "Numerical analysis of blood flow in 3-D arterial bifurcations". Thesis, City University London, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316023.
Pełny tekst źródła
10
Hinsdale, Taylor A. "Laser Speckle Imaging: A Quantitative Tool for Flow Analysis". DigitalCommons@CalPoly, 2014. https://digitalcommons.calpoly.edu/theses/1251.
Pełny tekst źródłaStreszczenie:
Laser speckle imaging, often referred to as laser speckle contrast analysis (LASCA), has been sought after as a quasi-real-time, full-field, flow visualization method. It has been proven to be a valid and reliable qualitative method, but there has yet to be any definitive consensus on its ability to be used as a quantitative tool. The biggest impediment to the process of quantifying speckle measurements is the introduction of additional non dynamic speckle patterns from the surroundings. The dynamic speckle pattern under investigation is often obscured by noise caused by background static speckle patterns. One proposed solution to this problem is known as dynamic laser speckle imaging (dLSI). dLSI attempts to isolate the dynamic speckle signal from the previously mentioned background and provide a consistent dynamic measurement. This paper will investigate the use of this method over a range of experimental and simulated conditions. While it is believable that dLSI could be used quantitatively, there were inconsistencies that arose during analysis. Simulated data showed that if the mixed dynamic and static speckle patterns were modeled as the sum of two independent speckle patterns, increasing static contributions led to decreasing dynamic contrast contributions, something not expected by theory. Experimentation also showed that there were scenarios where scattering from the dynamic media obscured scattering from the static medium, resulting in poor estimates of the velocities causing the dynamic scattering. In light of these observations, steps were proposed and outlined to further investigate into this method. With more research it should be possible to create a set of conditions where dLSI is known be accurate and quantitative.
11
Logan, J. F. J. "Vascular mechanisms in glaucoma - a phenotype and genotypic analysis". Thesis, Queen's University Belfast, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.246424.
Pełny tekst źródła
12
Hollander, Ellen Herdis. "Wave-intensity analysis of pulmonary arterial blood flow in anesthetized dogs". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ31035.pdf.
Pełny tekst źródła
13
Lee, Ka Wai. "Numerical analysis of blood flow and wall mechanics in stenosed arteries". Thesis, Imperial College London, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.398341.
Pełny tekst źródła
14
Smith, Leonard. "A system for the acquisition and digital analysis of lower limb flow waveforms". Master's thesis, University of Cape Town, 1994. http://hdl.handle.net/11427/27049.
Pełny tekst źródłaStreszczenie:
A PC based waveform acquisition and analysis system has been developed for use in aorta-iliac arterial assessment. A Motorola DSP56001 based system containing dual Analog to Digital converters is used to sample phase quadrature demodulated signals from a commercially available continuous wave Doppler unit. The Power Spectral Density is calculated using an autoregressive model from which the mean velocity waveform is calculated. This waveform is used to calculate the damping factor, vessel compliance and runoff resistance of a simple electrical model of the lower limb arterial circulation using a non-linear regression technique of curve fitting in the time domain. A pilot study using the system shows a significant separation (p < 0.001 Mann Whitney U-test) between the damping factors of a normal control group (quartile range = 0. 15 - 0.25 ; median = 0. 19) and a patient group with angiographically determined aorta-iliac arterial disease (quartile range = 0.45 - 0.89 ; median= 0.49).
15
Fisico, Alfredo Odon Rodriguez Ingeniero. "Determination of flow with echo-planar imaging". Thesis, University of Nottingham, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363605.
Pełny tekst źródła
16
Nik, Mohamed Nik Elena. "Investigation of blood dynamics : surface flow and droplet stain morphology on fabrics". University of Western Australia. Centre for Forensic Science, 2009. http://theses.library.uwa.edu.au/adt-WU2009.0112.
Pełny tekst źródłaStreszczenie:
This thesis is divided into two parts, each of which examines aspects of bloodstain analysis where gravity is the main force applied to blood. Part I is a preliminary study on the dynamics of blood flow on various inclined surfaces and examines the use of blood analogs for easy test replication. The flow of uncoagulated human blood at different volumes and temperatures was examined on wood at a set angle of 1.5°, and on glass at varying incline angles. Glycerol solutions of 59% and 42% were used to represent blood at 23°C and 37°C respectively. Glycerol flow trials of similar volumes were conducted on wood, PVC and glass. Fluid flow plots of distance versus time exhibited double exponential curve behaviour, although a power-law relationship derived by H. E. Huppert's (1982) flow expression was obtained for blood flowing on inclined wood. Blood flow exhibited several observable characteristics; a decreasing width of the leading edge over time, and streaking and component separation of the leading region at very low speeds. On a glass surface, the width of the initial flow region decreased and initial speed increased with increasing angles. The glycerol analogs used in this study did not represent their blood counterparts well due to differences in physical properties of the fluids. Part II of this study focuses on the forensic value of passive bloodstains on three fabrics; 100% cotton drill, 65/35 polyester cotton, and 100% Shantung silk. 26 µL drops of 37°C human blood were deposited onto the three fabrics and paper from a height of 14 cm at various impact angles. The stains were photographed and analysed qualitatively and quantitatively using computational methods. 100% cotton drill, 65/35 polyester cotton and ironed 100% Shantung silk provided useful forensic values such as direction of travel and angle of impact. Overall, this study has provided useful preliminary data for further research work.
17
Deparis, Simone. "Numerical analysis of axisymmetric flows and methods for fluid-structure interaction arising in blood flow simulation /". [S.l.] : [s.n.], 2004. http://library.epfl.ch/theses/?display=detail&nr=2965.
Pełny tekst źródła
18
Tingying, Peng. "Signal processing methods for the analysis of cerebral blood flow and metabolism". Thesis, University of Oxford, 2009. http://ora.ox.ac.uk/objects/uuid:ca84ac5b-7df0-488d-b390-d6f4f6e3ee52.
Pełny tekst źródłaStreszczenie:
An important protective feature of the cerebral circulation is its ability to maintain sufficient cerebral blood flow and oxygen supply in accordance with the energy demands of the brain despite variations in a number of external factors such as arterial blood pressure, heart rate and respiration rate. If cerebral autoregulation is impaired, abnormally low or high CBF can lead to cerebral ischemia, intracranial hypertension or even capillary damage, thus contributing to the onset of cerebrovascular events. The control and regulation of cerebral blood flow is a dynamic, multivariate phenomenon. Sensitive techniques are required to monitor and process experimental data concerning cerebral blood flow and metabolic rate in a clinical setting. This thesis presents a model simulation study and 4 related signal processing studies concerned with CBF regulation. The first study models the regulation of the cerebral vasculature to systemic changes in blood pressure, dissolved blood gas concentration and neural activation in a integrated haemodynamic system. The model simulations show that the three pathways which are generally thought to be independent (pressure, CO₂ and activation) greatly influence each other, it is vital to consider parallel changes of unmeasured variability when performing a single pathway study. The second study shows how simultaneously measured blood gas concentration fluctuations can improve the accuracy of an existing frequency domain technique for recovering cerebral autoregulation dynamics from spontaneous fluctuations in blood pressure and cerebral blood flow velocity. The third study shows how the continuous wavelet transform can recover both time and frequency information about dynamic autoregulation, including the contribution of blood gas concentration. The fourth study shows how the discrete wavelet transform can be used to investigate frequency-dependent coupling between cerebral and systemic cardiovascular dynamics. The final study then uses these techniques to investigate the systemic effects on resting BOLD variability. The general approach taken in this thesis is a combined analysis of both modelling and data analysis. Physiologically-based models encapsulate hypotheses about features of CBF regulation, particularly those features that may be difficult to recover using existing analysis methods, and thus provide the motivation for developing both new analysis methods and criteria to evaluate these methods. On the other hand, the statistical features extracted directly from experimental data can be used to validate and improve the model.
19
Fatona, Oluwatoyin Fadeke. "Analysis of morphological and blood flow characteristics of the human thoracic aorta". Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/58352.
Pełny tekst źródłaStreszczenie:
The human aorta is often affected by many cardiovascular diseases, including atherosclerosis, aneurysm and dissection. There is considerable evidence suggesting that these diseases are associated with the morphology and haemodynamic functions of the aorta, but not all these parameters can be measured directly in vivo. In particular, the helical flow characteristics and haemodynamic wall parameters can only be evaluated from quantitative information on a flow field resolved both in space and time. This study provides a comprehensive analysis of geometric and haemodynamic characteristics of the human aorta through subject-specific simulations of blood flow based on medical images. Computational fluid dynamics (CFD) models of the thoracic aorta were developed based on in vivo anatomical and flow data acquired using magnetic resonance imaging (MRI). In order to capture potential transitional and turbulent flow in the aorta, the correlation based shear stress transporttransitional (SST-Trans) turbulence model was employed. Detailed flow analyses were performed on multiple cases of normal thoracic aortas with a tricuspid aortic valve (TAV) and abnormal aorta with a bicuspid aortic valve (BAV). Results obtained from this study gave quantitative insights into the flow distributions and wall shear stress (WSS) patterns in normal and abnormal aortas. Morphological features and flow patterns of the TAV and BAV aortas were compared. In addition to standard flow parameters, specific indices were evaluated to allow for direct comparisons between the two groups; these included flow reversal ratio (FRR), helicity flow index (HFI) and shear range index (SRI). The results showed that all examined aortas tapered from the proximal ascending segment to the distal descending segment, with the BAV aorta showing a more distinct tapering. Although flow patterns were qualitatively similar in the TAV and BAV aortas, there were substantial quantitative variations. Highly disturbed flow was observed in all examined aortas during part of the cycle, mostly in the systolic deceleration phase. Predicted WSS was higher in the TAV aorta than in the BAV aorta, with the highest WSS occurring in regions around the major arch branches. Comparisons between the predicted and measured velocities showed a good agreement, demonstrating that MR image-based CFD modelling methodology can be used to obtain reliable haemodynamic parameters that are important in clinical assessment and management of aortic diseases.
20
Cape, Edward Gene. "Theoretical and experimental analysis of intracardiac jets : new techniques for noninvasive quantification of valvular insufficiency". Diss., Georgia Institute of Technology, 1991. http://hdl.handle.net/1853/11310.
Pełny tekst źródła
21
Chetlur, Adithya Prashanth. "A Novel Framework to Determine Physiological Signals From Blood Flow Dynamics". Scholar Commons, 2018. https://scholarcommons.usf.edu/etd/7610.
Pełny tekst źródłaStreszczenie:
Centers for Disease Control and Prevention (CDC) estimate that more than 11.2 million people require critical and emergency care in the United States per year. Optimizing and improving patient morbidity and mortality outcomes are the primary objectives of monitoring in critical and emergency care. Patients in need of critical or emergency care in general are at a risk of single or multiple organ failures occurring due to a traumatic injury, a surgical event, or an underlying pathology that results in severe patient hemodynamic instability. Hence, continuous monitoring of fundamental cardiovascular hemodynamic parameters, such as heart rate, respiratory rate, blood pressure, blood oxygenation and core temperature, is essential to accomplish diagnostics in critical and emergency care. Today’s standard of care measures these critical parameters using multiple monitoring technologies.
Though it is possible to measure all the fundamental cardiovascular hemodynamic parameters using the blood flow dynamics, its use is currently only limited to measuring continuous blood pressure. No other comparable studies in the literature were successful in quantifying other critical parameters from the blood flow dynamics for a few reasons. First, the blood flow dynamics exhibit a complicated and sensitive dynamic pressure field. Existing blood flow based data acquisition systems are unable to detect these sensitive variations in the pressure field. Further, the pressure field is also influenced by the presence of background acoustic interference, resulting in a noisy pressure profile. Thus in order to extract critical parameters from this dynamic pressure field with fidelity, there is need for an integrated framework that is composed of a highly sensitive data acquisition system and advanced signal processing. In addition, existing state-of-the-art technologies require expensive instrumentation and complex infrastructure. The information sensed using these multiple monitoring technologies is integrated and visualized using a clinical information system. This process of integration and visualization creates the need for functional interoperability within the multiple monitoring technologies. Limited functional interoperability not only results in diagnostic errors but also their complexity makes it impossible to use such technologies to accomplish monitoring in low resource settings. These multiple monitoring technologies are neither portable nor scalable, in addition to inducing extreme patient discomfort. For these reasons, existing monitoring technologies do not efficiently meet the monitoring and diagnostic requirements of critical and emergency care.
In order to address the challenges presented by existing blood flow based data acquisition systems and other monitoring systems, a point of care monitoring device was developed to provide multiple critical parameters by means of uniquely measuring a physiological process. To demonstrate the usability of this novel catheter multiscope, a feasibility study was performed using an animal model. The corresponding results are presented in this dissertation. The developed measurement system first acquires the dynamics of blood flow through a minimally invasive catheter. Then, a signal processing framework is developed to characterize the blood flow dynamics and to provide critical parameters such as heart rate, respiratory rate, and blood pressure. The framework used to extract the physiological data corresponding to the acoustic field of the blood flow consisted of a noise cancellation technique and a wavelet based source separation. The preliminary results of the acoustic field of the blood flow revealed the presence of acoustic heart and respiratory pulses. A unique and novel framework was also developed to extract continuous blood pressure from the pressure field of the blood flow. Finally, the computed heart and respiratory rates, systolic and diastolic pressures were benchmarked with actual values measured using conventional devices to validate the measurements of the catheter multiscope.
In summary, the results of the feasibility study showed that the novel catheter multiscope can provide critical parameters such as heart rate, respiratory rate and blood pressure with clinical accuracy. In addition, this dissertation also highlights the diagnostic potential of the developed catheter multiscope by presenting preliminary results of proof of concept studies performed for application case studies such as sinus rhythm pattern recognition and fetal monitoring through phonocardiography.
22
Jun, Yang. "Analysis and Visualization of the Two-Dimensional Blood Flow Velocity Field from Videos". Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/32539.
Pełny tekst źródłaStreszczenie:
We estimate the velocity field of the blood flow in a human face from videos. Our approach first performs spatial preprocessing to improve the signal-to-noise ratio (SNR) and the computational efficiency. The discrete Fourier transform (DFT) and a temporal band-pass filter are then applied to extract the frequency corresponding to the subjects heart rate. We propose multiple kernel based k-NN classification for removing the noise positions from the resulting phase and amplitude maps. The 2D blood flow field is then estimated from the relative phase shift between the pixels. We evaluate our approach about segmentation as well as velocity field on real and synthetic face videos. Our method produces the recall and precision as well as a velocity field with an angular error and magnitude error on the average.
23
Abatay, Hasan. "Analysis of the role of nitric oxide in the control of blood flow". Thesis, University of Oxford, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.540086.
Pełny tekst źródła
24
Wang, Ying. "Analysis of venous blood flow and deformation in the calf under external compression". Thesis, Imperial College London, 2011. http://hdl.handle.net/10044/1/7080.
Pełny tekst źródłaStreszczenie:
Deep vein thrombosis (DVT) is a common post-operative complication, and a serious threat to the patient’s general recovery. In recent years, there has been increasing awareness of the risk of DVT in healthy individuals after prolonged immobility, such as people taking long-period flights or sitting at a computer. Mechanical methods of DVT prophylaxis, such as compression stockings, have gained widespread acceptance, but the haemodynamic mechanism of their action is still not well understood. In this study, computational modelling approaches based on magnetic resonance (MR) images are used to (i) predict the deformation of calf and deep veins under external compression, (ii) determine blood flow and wall shear stress in the deep veins of the calf, and (iii) quantify the effect of external compression on flow and wall shear stress in the deep veins. As a first step, MR images of the calf obtained with and without external compression were analysed, which indicated different levels of compressibility for different calf muscle compartments. A 2D finite element model (FEM) with specifically tailored boundary conditions for different muscle components was developed to simulate the deformation of the calf under compression. The calf tissues were described by a linear elastic model. The simulation results showed a good qualitative agreement with the measurements in terms of deep vein deformation, but the area reduction predicted by the FEM was much larger than that obtained from the MR images. In an attempt to improve the 2D FEM, a hyperelastic material model was employed and a finite element based non-rigid registration algorithm was developed to calculate the bulk modulus of the calf tissues. Using subject-specific bulk modulus derived with this method together with a hyperelastic material model, the numerical results showed better quantitative agreement with MR measured deformations of deep veins and calf tissues. In order to understand the effect of external compression on flow in the deep veins, MR imaging and real-time flow mapping were performed on 10 healthy volunteers before and after compression. Computational fluid dynamics was then employed to calculate the haemodynamic wall shear stress (WSS), based on the measured changes in vessel geometry and flow waveforms. The overall results indicated that application of the compression stocking led to a reduction in both blood flow rate and cross sectional area of the peroneal veins in the calf, which resulted in an increase in WSS, but the individual effects were highly variable. Finally, a 3D fluid-structure interactions (FSI) model was developed for a segment of the calf with realistic geometry for the calf muscle and bones but idealised geometry for the deep vein. The hyperelastic material properties evaluated previously were employed to describe the solid behaviours. Some predictive ability of the FSI model was demonstrated, but further improvement and validation are still needed.
25
Liu, Dan. "Computational analysis of blood flow and oxygen transport in the retinal arterial network". Thesis, Imperial College London, 2010. http://hdl.handle.net/10044/1/6033.
Pełny tekst źródłaStreszczenie:
Pathological changes in retinal microvasculature are known to be associated with systemic diseases such as hypertension and diabetes, and may result in potentially disadvantageous blood flow and impair oxygen distribution. Therefore, in order to improve our understanding of the link between systemic diseases and the retinal circulation, it is necessary to develop an approach to quantitatively determine the hemodynamic and oxygen transport parameters in the retinal vascular circulation. This thesis aims to provide more insights into the detailed hemodynamic features of the retinal arterial tree by means of non-invasive imaging and computational modelling. It covers the following two aspects: i) 3D reconstruction of the retinal arterial tree, and ii) development of an image-based computational model to predict blood flow and oxygen transport in realistic subject-specific retinal arterial trees. The latter forms the main body of the thesis. 3D reconstruction of the retinal arterial tree was performed based on retinal images acquired in vivo with a fundus camera and validated using a simple 3D object. The reproduction procedure was found to be feasible but with limited accuracy. In the proposed 2D computational model, the smaller peripheral vessels indistinguishable from the retinal images were represented by self-similar asymmetric structured trees. The non-Newtonian properties of blood, and nonlinear oxyhemoglobin dissociation in the red blood cells and plasma were considered. The simulation results of the computational model were found in good agreement with in vivo measurements reported in the literature. In order to understand the effect of retinal vascular structure on blood flow and oxygen transport, the computational model was applied to subject-specific geometries for a number of hypertensive and diabetic patients, and comparisons were made with results obtained from healthy retinal arterial networks. Moreover, energy analysis of normal and hypertensive subjects was performed using 3D hypothetical models. Finally, the influence of different viscosity models on flow and oxygen transport in a retinal tree and the advantage of low dimensional models were examined. This study has demonstrated the applicability of the image-based computational modelling to study the hemodynamics and oxygen distribution in the retinal arterial network.
26
Cheng, Zhuo. "Analysis of blood flow in patient-specific models of type B aortic dissection". Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/9178.
Pełny tekst źródłaStreszczenie:
Aortic dissection is the most common acute catastrophic event affecting the aorta. The majority of patients presenting with an uncomplicated type B dissection are treated medically, but 25% of these patients develop subsequent dilatation and aortic aneurysm formation. The reasons behind the long‐term outcomes of type B aortic dissection are poorly understood. As haemodynamic factors have been involved in the development and progression of a variety of cardiovascular diseases, the flow phenomena and environment in patient‐specific models of type B aortic dissection have been studied in this thesis by applying computational fluid dynamics (CFD) to in vivo data. The present study aims to gain more detailed knowledge of the links between morphology, flow characteristics and clinical outcomes in type B dissection patients. The thesis includes two parts of patient‐specific study: a multiple case cross‐sectional study and a single case longitudinal study. The multiple cases study involved a group of ten patients with classic type B aortic dissection with a focus on examining the flow characteristics as well as the role of morphological factors in determining the flow patterns and haemodynamic parameters. The single case study was based on a series of follow‐up scans of a patient who has a stable dissection, with an aim to identify the specified haemodynamic factors that are associated with the progression of aortic dissection. Both studies were carried out based on computed tomography images acquired from the patients. 4D Phase‐contrast magnetic resonance imaging was performed on a typical type B aortic dissection patient to provide detailed flow data for validation purpose. This was achieved by qualitative and quantitative comparisons of velocity‐encoded images with simulation results of the CFD model. The analysis of simulation results, including velocity, wall shear stress and turbulence intensity profiles, demonstrates certain correlations between the morphological features and haemodynamic factors, and also their effects on long‐term outcomes of type B aortic dissections. The simulation results were in good agreement with in vivo MR flow data in the patient‐specific validation case, giving credence to the application of the computational model to the study of flow conditions in aortic dissection. This study made an important contribution by identifying the role of certain morphological and haemodynamic factors in the development of type B aortic dissection, which may help provide a better guideline to assist surgeons in choosing optimal treatment protocol for individual patient.
27
Routh, H. F. "Scattering of ultrasound by blood with reference to the analysis of doppler signals". Thesis, Bucks New University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.380271.
Pełny tekst źródła
28
Faddoul, R. Y. "A high frequency ultrasound pulsed doppler system for the measurement of skin blood flow". Thesis, University of Manchester, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355397.
Pełny tekst źródła
29
Schlindwein, Fernando Soares. "Real-time digital processing of Doppler ultrasound signals and its application to blood flow measurement". Thesis, University of Leicester, 1990. http://hdl.handle.net/2381/34225.
Pełny tekst źródłaStreszczenie:
A system comprising of a personal microcomputer and a Digital Signal Processor board has been assembled and programmed for real-time spectral analysis of Doppler ultrasound signals. Three spectrum analysis techniques were implemented to run in real-time on the system: The fast Fourier transform (FFT), the autoregressive (AR) model, and the moving average (MA) model. The FFT and the AR techniques were investigated in some depth. The advantages of using such a system are that it is entirely programmable, cheap, reliable, and that the processed information can be stored on diskettes. The inputs to the system are the forward and reverse components of the Doppler ultrasonic signal, and the outputs are the sonogram, the frequency envelope, and the intensity weighted mean frequency curve, which are presented on the screen and can be saved to diskette. Five frequency ranges can be selected by the operator, from 1.28 kHz to 20.48 kHz, corresponding to sampling frequencies from 2.56 kHz to 40.96 kHz. Most commercial systems for real-time spectral analysis of Doppler ultrasonic signals implement the modified FFT-periodogram technique for power spectral density estimation (PSDE), which is computationally very efficient but has some shortcomings, especially for the analysis of relatively short records. With the AR model approach the spectra can be estimated from short segments, no antileakage window is necessary and the spectral resolution is better than for the FFT. A study of some methods for order selection used with the autoregressive model for the spectrum analysis of Doppler signals is reported and the use of a fixed order of around 12 is suggested for the AR model. The implementation of the AR PSDE approach in real-time, in a reasonably priced system, is a step towards the practical use of the so called 'modern techniques' for spectral analysis of Doppler ultrasonic signals, but further work has to be done on the validation of the technique in clinical usage.
30
Elwell, Clare Elizabeth. "Measurement and data analysis techniques for the investigation of adult cerebral haemodynamics using near infrared spectroscopy". Thesis, University College London (University of London), 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.244793.
Pełny tekst źródła
31
Lima, R. "Analysis of the blood flow behavior through microchannels by a confocal micro-PIV/PTV system". Doctoral thesis, Tohoku University, 2007. http://hdl.handle.net/10198/1263.
Pełny tekst źródłaStreszczenie:
Over the years, various experimental methods have been applied in an effort to understand the blood flow behavior in microcirculation. Most of our current knowledge in microcirculation is based on macroscopic flow phenomena such as Fahraeus effect and Fahraeus-Linqvist effect. The development of optical experimental techniques has contributed to obtain explanations on the way the blood flows through microvessels. Although the past results have been encouraging, detailed studies on the flow properties of blood in the microcirculation has been limited by several technical factors such as poor spatial resolution and difficulty to obtain quantitative detailed measurements at such small scales. Therefore, there is still a lack of knowledge on the microscale flow behavior of blood cells through microvessels.
In recent years, due to advances in computers, optics, and digital image processing techniques, it has become possible to combine a particle image velocimetry (PIV) system with a conventional microscope. As a result, this combination, known as a micro-PIV, has greatly increased the resolution of the conventional PIV. Although the conventional micro-PIV technique has proven to be useful in measuring the flow behavior in microfluidics devices, the entire flow field is illuminated and consequently the out-of-focus emitted light can result in high levels of background noise, which degrades the measured velocity fields. More recently, considerable progress in the development of confocal microscopy and the advantages of this technique over conventional microscopy have led to a new technique known as confocal micro-PIV. This technique combines the conventional PIV system with a spinning disk confocal microscope (SDCM), which has the ability to obtain in-focus images with an optical thickness less than 1 m (optical sectioning effect) and also to improve the particle image contrast, definition, and spatial resolution. This emerging technique has been successfully applied to measure homogenous fluids, however the question whether a confocal micro-PIV system is a suitable technique to study the blood flow behavior through microchannels remains.
In our work, a confocal micro-PIV system and also a confocal micro-particle tracking velocimetry (PTV) system are used, for the first time, to investigate in vitro blood flow through microchannels. By using these systems we have aimed to obtain further insights into the complex flow properties of blood in the microcirculation with the expectation that a better understanding on the blood flow phenomena will make a contribution to the prevention, diagnosis, and treatment of vascular diseases.
The validity of our confocal micro-PIV system is performed by comparing the experimental results of pure water seeded with tracer particles with an established analytical solution for a steady flow in a long straight microchannel. Good agreement was obtained, especially around the centre of the microchannel, with errors on the order of 5% or less. Furthermore, we have also demonstrated, for the first time, the ability of the confocal micro-PIV to generate 3D velocity profiles of a blood cell suspension fluid ( 4% haematocrit (Hct)).
The confocal system is used to determine both ensemble and instantaneous velocity profiles for in vitro blood (haematocrit up to 17%), flowing through a 100-m square glass microchannel at a constant flow rate and low Reynolds number (Re = 0.025). It was observed small fluctuations in the instantaneous velocity profiles which were found to be closely related to the increase with the Hct. Although the micro-PIV community tend to ignore these fluctuations, this study shows that the root mean square (RMS) values increase with the haematocrit implying that the presence of RBCs within the plasma flow strongly influences the measurements of the instantaneous velocity fields. Consequently, information provided by instantaneous velocities should be taken into account. Furthermore, by measuring the velocity profiles in vitro blood (20% Hct) in a rectangular (300 m wide, 45 m deep) polydimethysiloxane (PDMS) microchannel, small fluctuations were also found in the velocity profiles. Therefore, our results clearly show evidence that the encountered fluctuations are closely related to the motion and interaction of RBCs when flowing in a crowded environment.
We show that the confocal micro-PIV system is able to measure with good accuracy the blood plasma flow with Hct up to 9%, in a 100 m square microchannel. However, for Hct bigger than 9%, the light absorbed and scattered by the RBCs contributes to diminish the concentration of tracer particles in the acquired confocal images. Hence, a novel approach was implemented to the confocal system in order to obtain more reliable quantitative measurements on the motion of blood cells at high suspensions of RBCs. By using labeled RBCs and Dextran-40, a confocal micro-PTV system was employed, for the first time, in an effort to track individual tracer cells at high concentration suspensions of RBCs. The ability of the confocal system to generate thin in-focus planes has allowed both qualitative and quantitative measurements in flowing blood at concentrated suspensions (up to 35% Hct) of cell-cell hydrodynamic interaction, RBC orientation and RBC radial dispersion at different depths. Such data is thought to be extremely relevant to elucidate the blood transport mechanisms and associated diseases such as thrombosis and atherosclerosis.
By using the confocal micro-PTV system, the RBCs radial dispersion coefficient (Dyy) was measured in the middle plane of a 50m and 100 m glass capillaries in both diluted and concentrated suspensions (Hcts up to 35%) at low Reynolds numbers (Re from 0.003 to 0.005). There is evidence that the RBCs Dyy tends to increase with the Hct but, at Hct of about 25%, it tends to level off. This finding suggests that, at moderate Hcts, the development of the plasma layer and the consequent decrease of the local cell density, surrounding the RBCs, may enhance the radial dispersion of RBCs. In addition, we have also found that Dyy is greatest at radial positions between 0.4R to 0.8R, whereas at locations adjacent to wall (0.8R to 1R) and around the middle of the capillary (0R to 0.2R) the paths of the tracer RBCs tend to exhibit lower radial displacements. Furthermore, our results also provide evidence that RBCs Dyy tends to decrease with the diameter. This phenomenon is believed to be due to Hct reduction with the diameter (Faharaeus effect) and also to geometry constrictions which limit the amplitude of the RBCs radial displacements. Hence, this finding seems to indicate that the reduction of RBC radial dispersion may be linked to the decrease in apparent viscosity with decreasing diameter (Faharaeus-Lindqvist effect).
The work reported in this thesis represents the first application of a confocal micro-PIV/PTV system to study the blood flow behavior through microchannels. The confocal system proves to be able to eliminate the problems and concerns of the experimental techniques used in the past and provide additional detailed description on the RBC motion not obtainable by other conventional methods. Finally, the research carried out throughout this thesis provides the basis not only to obtain further insights on the blood mass transport mechanisms under both physiological and pathological conditions but also to improve the existing theories, models, and computer simulations on the blood flow at both micro and macroscale levels.The Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT); The Science and Technology Foundation (FCT)
32
Folarin, Amos Akinola. "Analysis of tumour angio-architecture and blood flow using microcomputed tomography and lattice Boltzmann simulations". Thesis, University College London (University of London), 2008. http://discovery.ucl.ac.uk/1444208/.
Pełny tekst źródłaStreszczenie:
The precise architecture of the vascular system is critical to its many specialised functions. In sharp contrast tumour vascular architecture is highly disorganised and dysfunctional. The reason for this is the grossly abnormal angiogenic signalling prevalent in the tumour microenvironment. Aberrant tumour vasculature is a key determinant of spatial and temporal heterogeneities of blood flows. Additionally, irregularities in the tumour vascular wall, a lack of functional lymphatics and a severely retarded trans-mural hydrostatic pressure gradient also diminish convective transport out of the vessels. Diffusion therefore remains the dominant transport mode in tumours and presents a considerable barrier to macromolecular therapy (e.g. Antibody-directed enzyme prodrug therapy (ADEPT)). A number of recent studies of vascular morphology in both clinical and xenograft tumours have demonstrated the existence of type-specific architectures. Precisely how these type-specific architectures translate to blood flow through the vascular system had not been determined. To address this we have developed a method for studying the 3D architecture of the tumour and simulating flows through it. This technique uses corrosion casts to capture the 3D tumour vascular system. 3D morphometry was determined by stereoimaging and X-ray micro-computed tomography. A computational fluid dynamics model was then used to study the hydrodynamics of the vascular networks. My results show that vessel structure and architecture varies in clinical colon cancers, but these differences were substantially smaller than those of two human colorectal xenografts (LS147T and SW1222) commonly used in pre-clinical studies. The results also provide evidence that LS147T is, in general, a closer model to most clinical colorectal tumours than SW1222. To our knowledge this is the first attempt to utilise X-ray micro-computed tomography to study vascular corrosion casts of tumours, and using this data, produce 3D flow profiles.
33
Wang, Jiaqiu. "Image-based patient-specific computational biomechanical analysis of the interaction between blood flow and atherosclerosis". Thesis, Queensland University of Technology, 2020. https://eprints.qut.edu.au/202017/1/Jiaqiu_Wang_Thesis.pdf.
Pełny tekst źródłaStreszczenie:
This research focuses on the development of a biomechanical strategy for risk assessment of atherosclerotic plaque rupture, which is a leading cause of acute cardiovascular events, such as heart attack and stroke. Image-based three-dimensional coronary and carotid arterial models were developed, and computational biomechanical analysis was performed to evaluate the mechanical interaction between blood flow and atherosclerosis. This study uncovered the biomechanical risk factors that are associated with high-risk atherosclerosis and provided a biomechanical tool for detecting high-risk plaques. It will help with future clinical diagnosis and treatment of cardiovascular diseases.
34
Christophe, Jean-Joseph. "Patient-specific morphological and blood flow analysis of pulmonary artery in the case of pneumothorax". Paris 6, 2011. http://www.theses.fr/2011PA066255.
Pełny tekst źródłaStreszczenie:
Le pneumothorax se caractérise par l’affaissement d’un poumon. A ce jour, l’effet morphologique et hémodynamique du pneumothorax sur les artères pulmonaires reste peu compris. La géométrie des artères a été extraite et reconstruite à partir d’images tomographiques de trois patients. Différents paramètres géométriques ont été calculés. La forme du tronc et des branches de l’artère pulmonaire a été fortement affectée. Pour clarifier l’effet des perturbations géométriques sur le flux sanguin, les équations de Navier Stokes pour un flux stable laminaire ont été résolues en introduisant une résistance aux sorties. Nous avons observé une diminution du ratio de flux dans le poumon affecté lors d’un accroissement de la résistance. De ce fait, l’oxygénation dans les artères systémiques dépend davantage du poumon sain, entrainant une amélioration de cette oxygénation. Ces résultats devraient permettre une meilleure compréhension du fonctionnement de la ventilation dans le cas d’un pneumothorax.
35
Carrig, Pauline Elize. "The effect of blood chemistry on the rheological properties of the fluid". Thesis, Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/94451.
Pełny tekst źródłaStreszczenie:
A four variable constitutive equation was developed utilizing the method first presented by Schneck and Walburn. Spearman rank correlation coefficients were calculated on whole blood samples within a narrow range of hematocrit to investigate further the effect of the various plasma constituents on whole blood viscosity.
Viscosity measurements were made on one hundred anticoagulated blood samples of known hematocrit and chemical composition. The constitutive equation was developed using a power law functional form similar to that employed by Schneck and Walburn. This equation contains two parameters, the consistency index and the non-Newtonian index. A computerized multiple regression technique with apparent viscosity as the dependent variable was used to determine the particular form of these parameters.
The one, two and three variable models developed confirmed the results of the previous work of Schneck and Walburn. The four variable model included the total lipids in combination with the concentration of total protein minus albumin and hematocrit. Spearman rank correlation coefficients showed the highest correlations between whole blood viscosity and the plasma constituents to be those of the globulins, total protein and fibrinogen.
The constitutive equation developed did not show as high a correlation between experimental data and theory as did the Schneck-Walburn three variable model. The addition of a fourth variable did produce a statistically significant increase over the best three variable model of the present study.M.S.
36
Graça, Cristo dos Santos Lopes Ruano Maria da. "Investigation of real-time spectral analysis techniques for use with pulsed ultrasonic Doppler blood flow detectors". Thesis, Bangor University, 1992. https://research.bangor.ac.uk/portal/en/theses/investigation-of-realtime-spectral-analysis-techniques-for-use-with-pulsed-ultrasonic-doppler-blood-flow-detectors(f184d2a8-bde7-492a-b487-438704d3ea04).html.
Pełny tekst źródłaStreszczenie:
The goals of the work described here were the development of a method of selection of spectral estimation for use with pulsed Doppler ultrasonic blood flow instruments, and the use of this method to select an estimator and its implementation in a form suitable for real-time applications. A study of estimation accuracy of the mean frequency and bandwidth using a number of spectral estimators was carried out. Fourier based, parametric, and, minimum variance estimators were considered. A Doppler signal simulator was developed to allow the accuracy tests required. A method of selection of spectral estimators based on the accuracy of estimation of decisive signal parameters, under the constraint of low computational complexity has been proposed. This novel cost/benefit criterion, allows the possibility of weighting appropriate to estimator (mean frequency and bandwidth) and signal frequency importance (across the range of signal characteristics). For parametric spectral estimators, this criterion may also be used to select model order, leading to lower orders than FPE, AIC and CAT criteria. Its use led to the selection of a 4t' order modified covariance parametric method. A new version of the modified covariance method for spectral estimation of real signals was developed. This was created with a view to the parallel partitioning of the algorithm for parallel implementation on a transputer-based system, using OCCAM. A number of parallel topologies were implemented. Their performance was evaluated considering estimation of a single, and a sequence of Doppler signal segments, revealing the feasibility of these parallel implementations to be achieved in real-time.
37
David, Jean-Yves. "Modern spectral analysis techniques for blood flow velocity and spectral measurements with a 20 MHZ pulsed doppler ultrasound catheter". Thesis, Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/17791.
Pełny tekst źródła
38
Gariba, Munir Antonio. "Visualisation methods for the analysis of blood flow using magnetic resonance imaging and computational fluid dynamics". Thesis, Imperial College London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322530.
Pełny tekst źródła
39
Long, Xuguang. "Application of time-frequency analysis to Doppler ultrasound blood flow signals for detection of small stenoses". Thesis, King's College London (University of London), 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390610.
Pełny tekst źródła
40
Bathe, Mark 1975. "A fluid-structure interaction finite element analysis of pulsatile blood flow through a compliant stenotic artery". Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/9842.
Pełny tekst źródła
41
Singh, Shelly Deokie. "Computational analysis of blood flow and stress patterns in the aorta of patients with Marfan syndrome". Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/45539.
Pełny tekst źródłaStreszczenie:
Personalised external aortic root support (PEARS) was designed to prevent progressive aortic dilatation, and the associated risk of aortic dissection, in patients with Marfan syndrome by providing an additional support to the aorta. The objective of this thesis was to understand the biomechanical implications of PEARS surgery as well as to investigate the altered haemodynamics associated with the disease and its treatment. Finite element (FE) models were developed using patient-specific aortic geometries reconstructed from pre and post-PEARS magnetic resonance (MR) images of three Marfan patients. The wall and PEARS materials were assumed to be isotropic, incompressible and linearly elastic. A static load on the inner wall corresponding to the patients’ pulse pressure was applied with a zero-displacement constraint at all boundaries. Results showed that peak aortic stresses and displacements before PEARS were located at the sinuses of Valsalva but following PEARS surgery, they were shifted to the aortic arch, at the intersection between the supported and unsupported aorta. The zero-displacement constraint at the aortic root was subsequently removed and replaced with downward motion measured from in vivo images. This revealed significant increases in the longitudinal wall stress, especially in the pre-PEARS models. Computational fluid dynamics (CFD) models were developed to evaluate flow characteristics. The correlation-based transitional Shear Stress Transport (SST-Tran) model was adopted to simulate potential transitional and turbulence flow during part of the cardiac cycle and flow waveforms derived from phase-contrast MR images were imposed at the inlets. Qualitative patterns of the haemodynamics were similar pre- and post-PEARS with variations in mean helicity flow index (HFI) of -10%, 35% and 20% in the post-PEARS aortas of the three patients. A fluid-structure interaction (FSI) model was developed for one patient, pre- and post-PEARS in order to examine the effect of wall compliance on aortic flow as well as the effect of pulsatile flow on wall stress. This model excluded the sinuses and was based on the laminar flow assumption. The results were similar to those obtained using the rigid wall and static structural models, with minor quantitative differences. Considering the higher computational cost of FSI simulations and the relatively small differences observed in peak wall stress, it is reasonable to suggest that static structural models would be sufficient for wall stress prediction. Additionally, aortic root motion had a more profound effect on wall stress than wall compliance. Further studies are required to assess the statistical significance of the findings outlined in this thesis. Recommendations for future work were also highlighted, with emphasis on model assumptions including material properties, residual stress and boundary conditions.
42
Swanepoel, A. C. (Albe Carina). "Ultrstructural and flow cytometric analysis of platelets and fibrin networks during the menstrual cycle and pregnancy". Thesis, University of Pretoria, 2013. http://hdl.handle.net/2263/32969.
Pełny tekst źródłaStreszczenie:
INTRODUCTION: The menstrual cycle and pregnancy are processes unique to women. Both these processes involve various hormones as well as the coagulation system. Throughout normal pregnancy, platelet activation and increase in blood coagulation factors contributes to the hypercoagulable state observed on a physiological level. METHODS: Fibrin networks and platelets were analysed by electron microscopy and flow cytometry to determine any differences found in different phases of pregnancy compared to healthy control individuals. The fibrin networks from different phases of the menstrual cycle as well as different phases of pregnancy were investigated. RESULTS: It was found that ultrastructural changes in fibrin fiber morphology result from estrogen changes during the menstrual cycle. During pregnancy the minor thin fibers were prominent and thick matted layers of coagulant formation were evident. A large quantity of protein globular clusters similar to those seen in the menstrual cycle was present. Changes observed in platelet ultrastructure during pregnancy showed pregnancy-specific modifications. Platelets were activated and internal organelles showed variation from control participants. Flow cytometric analysis of platelets verified pregnancy-specific modifications. Close interactions between platelets and erythrocytes were evident. CONCLUSION: The female body is equipped to handle alterations in the coagulation system as can be extrapolated from the pregnancy-specific modifications. This study is the first to show alterations in fibrin network and platelet ultrastructure during and after pregnancy when compared to non-pregnant controls. The physiological changes during normal pregnancy can be used as a standard for comparison to abnormal or ailing pregnancy.Thesis (PhD)--University of Pretoria, 2013.
gm2013
Physiology
Unrestricted
43
Wright, Andrew William. "Umbilical arterial flow analysis to determine an index of placental impedance". Master's thesis, University of Cape Town, 1994. http://hdl.handle.net/11427/27050.
Pełny tekst źródłaStreszczenie:
Umbilical flow velocity waveforms (FVW' s) can be measured non-invasively using Doppler ultrasound. Changes in the FVW's occur long before the warning signs from other conventional monitoring methods. Correct interpretation of the changes in the FVW has the potential of providing the clinician with an early warning of foetal distress. A number of indices have been described in the literature to characterise the FVW including the Pulsatility Index (PI), the Resistance Index (RI) and more recently, the High Resistance State Index (HRSI). Researchers have shown a dependence of the FVW, and thus the indices which describe it, on factors such as the placental resistance (Muijsers et al 1990a) blood pressure pulsatility (Mulders et al 1986), and the foetal heart rate (Downing et al 1991). In order to model the foetal circulation, the dimensions of the foetal vessels were required. These were taken from the literature when available, but had to be supplemented by measurements on post mortem specimens. This information, together with blood pressures and flow rates taken from the literature, was used to design electrical analogous models of the foetal arterial circulation (model 1 and model 2), which were implemented using PSpice, which is an electronic circuit simulator package. The Flow Velocity Waveforms (FVW's) simulated were stored and then analyzed using MATLAB, which is a mathematical package to calculate the waveform indices and both the blood pressure and percentage blood flow to the different anatomical regions of the foetus. Model 1 is a simple model of the umbilical placental unit only, which assumes a rectified sine wave with a D.C. offset as an input waveform while Model 2 is a distributed element model of the complete foetal arterial system, including a realistic representation of the foetal heart. AIM: Simulations of the FVW were used to examine the effects of placental obliteration (raised placental resistance), placental size, foetal heart rate (FHR), blood pressure pulsatility (BPPI), mean blood pressure (BP), and site of measurement of the FVW along the umbilical artery and thus on the waveform indices which are used to describe it (RI, PI and HRSI). RESULTS/ DISCUSSION: The investigations using models 1 and 2 showed that the indices were significantly dependent on the placental resistance, the size of the placenta and the type of placental obliteration. Model 1 was also used to investigate the effect of FHR variations on the indices under the original assumption that the input waveform to the umbilical/placental unit was a rectified sinusoid offset by a constant voltage (D.C.) (Thompson and Trudinger 1990). The result obtained, that is, the FHR does not affect the indices (in particular the PI) needed further investigation because the assumption for the input waveform is not true under all conditions. For this reason, the simulations were repeated using model 2, with the interesting result that there is a difference between short term FHR variations and long-term FHR variation. Short term FHR variations had a pronounced effect on the indices. The blood pressure pulsatility and the indices concerned varied by large amounts in this case, which indicated a link between the blood pressure pulsatility and all the indices. Long term FHR variations had an inconsistent but small effect on the blood pressure pulsatility and in turn had a small effect on the RI and PI. The mean blood pressure in these simulations decreased with increasing FHR which resulted in a pronounced increase in the HRSI which indicated the dependency of this index on the mean blood pressure rather than on the blood pressure pulsatility. It was found that the HRSI is a good index of placental resistance and may be particularly useful in evaluating high placental resistance in cases of absent flow during diastole, since, in these cases it is only slightly affected by the FHR. A value of greater than 34 percent is the recommended HRSI value to indicate severe foetal distress. The results also indicate that the FVW shape varies along the umbilical artery and is far more pulsatile at the aortic (proximal) end than the placental end. This is reflected in the indices which thus have worst case values at the placental end. It is thus recommended that, where possible, the indices are measured at the placental end of the umbilical artery.
44
ROSSI, DOMENICO. "In-flow physical-morphological analysis of PBMC in microfluidic device by light scattering". Doctoral thesis, Politecnico di Torino, 2016. http://hdl.handle.net/11583/2644903.
Pełny tekst źródłaStreszczenie:
Morphological detailed informations of living blood cell are retrieved with an approach based on light scattering coupled to a cell 3D alignment in a centreline of a microfluidic self made apparatus. Cell’s informations are collected over a widespread angle, spanning from 2 to 30 degrees, with an angular resolution of 0.1022 degrees. Cells are investigated in their natural state, and such "label-free" approach of analysis significantly differs from other technique based on scattering of light, such as flow cytometry. Such a characterisation permits to obtain detailed informations, giving the possibility to discriminate cells with very similar physical characteristics between each other. Morphological analysis of single Red Blood Cells have been performed, obtaining precise determination in terms of dimension. Single White Blood Cells have been investigated as well , obtaining precise diameter characterization together with information regarding Refractive Index and amount of nucleus relative to the overall dimension of
the cell (Nucleus/Cytosol ratio). White Blood Cells have been also analysed in pathological conditions.
45
Miller, Brandon Lee. "Quantitative, Multiparameter Analysis of Fluorescently Stained, Negatively Enriched, Peripheral Blood from Cancer Patients". The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1386005404.
Pełny tekst źródła
46
Patz, Ralf. "Time-frequency analysis of Doppler ultrasound blood flow signals : an investigation into automated diagnosis of vascular disease". Thesis, University of South Wales, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289393.
Pełny tekst źródła
47
Celestin, Carey Jr. "Computational Fluid Dynamics Applied to the Analysis of Blood Flow Through Central Aortic to Pulmonary Artery Shunts". ScholarWorks@UNO, 2015. http://scholarworks.uno.edu/td/1972.
Pełny tekst źródłaStreszczenie:
This research utilizes CFD to analyze blood flow through pathways representative of central shunts, commonly used as part of the Fontan procedure to treat cyanotic heart disease. In the first part of this research, a parametric study of steady, Newtonian blood flow through parabolic pathways was performed to demonstrate the effect that flow pathway curvature has on wall shear stress distribution and flow energy losses. In the second part, blood flow through two shunts obtained via biplane angiograms is simulated. Pressure boundary conditions were obtained via catheterization. Results showed that wall shear stresses were of sufficient magnitude to initiate platelet activation, a precursor for thrombus formation. Steady results utilizing time-averaged boundary conditions showed excellent agreement with the time-averaged results obtained from pulsatile simulations. For the points of interest in this research, namely wall shear stress distribution and flow energy loss, the Newtonian viscosity model was found to yield acceptable results.
48
Köhler, Benjamin [Verfasser], i Bernhard [Akademischer Betreuer] Preim. "Guided qualitative and quantitative analysis of cardiac 4D PC-MRI blood flow data / Benjamin Köhler ; Betreuer: Bernhard Preim". Magdeburg : Universitätsbibliothek, 2016. http://d-nb.info/1118572181/34.
Pełny tekst źródła
49
Mutema, Jonsson Carla. "Evaluation of Flow Cytometric Methods Used in Analysis of Immune Cells in Patients with Malignant Lymphoma". Thesis, Uppsala universitet, Institutionen för kvinnors och barns hälsa, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-326010.
Pełny tekst źródłaStreszczenie:
Malignant lymphomas are a group of cancerous diseases that develop from lymphocytes and primarily affect lymph nodes. Being the sixth most common cancer type in Sweden, lymphoma is a societal problem that needs to be tackled by improving care and treatment of patients. This study was designed to examine the blood cell composition in lymphoma patients and well as determine whether the use of cryopreserved cells affected the analysis outcome. An evaluation of the methods used was also performed. Frozen peripheral blood from lymphoma patients as well as fresh and frozen blood from healthy controls was used. The cells of interest were monocytes, granulocytes, Treg, NKT, iNKT, B and T cells plus the dendritic cell activation protein CCR7. Three immunophenotyping methods were used. Method one was used in staining surface cell markers while the other two were for both surface and intracellular staining using two distinctive kits. The results showed no significant difference in immune cell composition between patients and blood donors. Limited patient samples and the lack of female blood donors could explain the unexpected result. A substantial difference in Treg cells was observed in fresh and frozen tested samples as well as T cell outcomes in method one compared to the other two methods. There were fewer Treg cells in frozen samples, which probably was due to cryopreservation while the lack of fixation in method one led to the loss of CD4+ T cells. Overall, the methods used were adequate but definitely require some improvements.
50
Carvalho, Julene de Souza. "Analysis of the clinical utility of a modified plethysmographic method for indirect measurement of instantaneous pulonary capillary blood flow". Thesis, Imperial College London, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362366.
Pełny tekst źródła