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1
Norris, David G. "NMR flow imaging." Thesis, University of Aberdeen, 1986. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU009818.
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The phase-encoded method of NMR flow imaging is examined in detail. The motion of isochromatic groups in the direction of suitably balanced magnetic field gradients will give a phase change in the NMR signal directly proportional to the velocity, acceleration, or higher derivative of position, dependent upon the form of the field gradient. If a simple bipolar pulse is used then the phase change, for isochromats moving with constant velocity, will be proportional to the velocity. If two such pulses are placed back to back then the phase change is proportional to the acceleration. The motion of isochromats in the magnetic field gradients used for imaging will also cause phase changes. These effects are considered, and simple methods of reducing them presented. Phase errors due to main field inhomogeneity are shown to be eliminated by a simple phase difference technique. In this two image data sets having different flow sensitivities are obtained, and the phase difference between them calculated. Velocity images were obtained using this technique, both by the manipulation of the frequency-encoding and selection gradients, and by the insertion of bipolar pulses in the imaging sequence. Acceleration images were also produced by adding double bipolar pulses to the imaging sequence. Both spin-echo and field-echo sequences were used. Field-echo sequences were shown to be superior for high velocities, particularly when the direction of flow is through the slice, otherwise spin-echo sequences were preferred. The Fourier imaging of velocity is also examined, and images presented. This technique is only considered to be useful for projective imaging, where it is shown to have an SNR advantage over established methods. Using two specially designed phantoms the accuracy of all these techniques is shown to be within 5%.
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Gates, Andrew R. C. "Blood flow studies using nuclear magnetic resonance imaging." Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260496.
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Sun, Shen. "Laser Doppler imaging and laser speckle contrast imaging for blood flow measurement." Thesis, University of Nottingham, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.604304.
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The two blood flow imaging techniques, laser Doppler blood flow imaging (LDI) and laser speckle contrast blood flow imaging (LSCI), are well established and broadly applied in medical research. They are similar as both detect and process a fluctuating interference (speckle) pattem. However, the difference between processing algorithms provides different imaging characteristics. LDI can provide accurate, quantitative blood flow measurement which is seldom achieved by LSCI. Nevertheless, the fast imaging speed and simple instrumental setup provided by LSCI overcome some of the limitations ofLDI. With the development of high frame rate cameras full field LDI is now feasible and with the development of new processing algorithms LSCI is now providing more accurate quantitative information. It is therefore important to compare the performance of these two techniques. A full-field LDI system based on an FPGA (Field Programmable Gate Array) coupled with a high-speed CMOS (Complementary Metal-Oxide-Semiconductor) camera chip has been developed which provides blood flow images with flexible frame rates and spatial resolution. When a high spatial resolution is required, 1280xl024-pixel blood flow images were obtained by processing up to 2048 samples at O.2fps (frame per second). Altematively, a maximum of 15.5fps was achieved by reducing the resolution and sampling points to 256x256 pixels and 128 samples respectively. As a generic full-field LDI system, several parts of the system (memory unit, processing unit) can be simply updated or transplanted to another platform. The resource usage is optimized by utilizing a mixture of fixed and floating-pointing implementations, and the imaging speed is maximised because of the design of streamline structure which enables continuous input of data. Images were obtained of rotating diffusers at different rotation velocities and the system provides a linear relationship with velocity. Human blood flow images are also demonstrated both of the finger and of a healing wound. The author-designed LDI system was then applied to a high-spatial resolution flow imaging application in which the mixture of water and polystyrene micro spheres was pumped through a micropipette (diameter = 250llm) with controlled velocities, and the resulting flow was imaged and processed. The accurate, high-spatial resolution flow measurement was demonstrated by the resulting flow images which are of size 1280x 1 024 pixels and obtained by processing 2048 samples at each pixel. Besides the LDI system, a novel LSCI system has been developed on the same platform, establishing a unique LDI and LSCI hybrid system. By developing the LSCI method with equivalent exposures, the LDI data can be analysed using LSCl processing, enabling a truly fair comparison of these two methodologies. For comparison, measurements were carried out on a rotating diffuser that simulates the human tissue with controlled parameters. Although LDI and LSCI are qualitatively similar, the lack of quantitative blood flow measurement ofLSCI was recognized from the comparison since LSCI is exposure time dependent and unable to linearly detect the velocity changes. 11 To improve the linearity and accuracy ofLSCI measurement, multi-exposure laser speckle contrast imaging (MLSCI) has been introduced. However this increases image acquisition time as consecutive images at different exposure times need to be acquired. On the basis of the novel LSCI method, a new MLSCI scheme has been invented. The advantage of the MLSCI is that each frame is exposed with a fixed duration and various exposure times are alternatively achieved by accumulating several successive frames. In this way, the requirement to obtain a wide range of exposure times from consecutive images is overcome. This reduces image acquisition time as it depends on the longest exposure time rather than the sum of all exposures. From measurements of a rotating diffuser, the MLSCI was demonstrated to be capable of quantitatively measuring flow changes as in LDI. III
4
Nguyen, Hoang Cuong. "High speed processing for laser doppler blood flow imaging." Thesis, University of Nottingham, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.517694.
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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.
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Shymkiw, Roxane Chia-Chi. "Measurement of blood flow in bone by laser Doppler imaging." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0021/MQ55267.pdf.
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Himsworth, John M. "Linear array CMOS detectors for laser Doppler blood flow imaging." Thesis, University of Nottingham, 2011. http://eprints.nottingham.ac.uk/12392/.
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Laser Doppler blood flow imaging is well established as a tool for clinical research. The technique has considerable potential as an aid to diagnosis and as a treatment aid in a number of situations. However, to make widespread clinical use of a blood flow imager feasible a number of refinements are required to make the device easy to use, accurate and safe. Existing LDBF systems consist of 2D imaging systems, and single point scanning systems. 2D imaging systems can offer fast image acquisition time, and hence high frame rate. However, these require high laser power to illuminate the entire target area with sufficient power. Single point scanning systems allow lower laser power to be used, but building up an image of flow in skin requires mechanical scanning of the laser, which results in a high image acquisition time, making the system awkward to use. A new approach developed here involves scanning a line along a target, and imaging the line with a 1D sensor array. This means that only one axis of mechanical scanning is required, reducing the scanning speed, and the laser power is vastly reduced from that required for a 2D system. This approach lends itself well to the use of integrated CMOS detectors, as the smaller pixel number means that a linear sensor array can be implemented on an IC which has integrated processing while keeping overall IC size, and hence cost, lower than equivalent 2D imaging systems. A number of front-end and processing circuits are investigated in terms of their suitability for this application. This is done by simulating a range of possible designs, including several logarithmic pixels, active pixel sensors and opamp-based linear front-ends. Where possible previously fabricated ICs using similar sensors were tested in a laser Doppler flowmetry system to verify simulation results. A first prototype IC (known as BVIPS1) implements a 64x1 array of buffered logarithmic pixels, chosen for their combination of sufficient gain and bandwidth and compact size. The IC makes use of the space available to include two front-end circuits per pixel, allowing other circuits to be prototyped. This allows a linear front-end based on opamps to be tested. It is found that both designs can detect changes in blood flow despite significant discrepancies between simulated and measured IC performance. However, the signal-noise ratio for flux readings is high, and the logarithmic pixel array suffers from high fixed pattern noise, and noise and distortion that makes vein location impossible. A second prototype IC (BVIPS2) consists of dual 64x1 arrays, and integrated processing. The sensor arrays are a logarithmic array, which addresses the problems of the first IC and uses alternative, individually selectable front-ends for each pixel to reduce fixed-pattern noise, and an array of opamp-based linear detectors. Simulation and initial testing is performed to show that this design operates as intended, and partially overcomes the problems found on the previous IC - the IC shows reduced fixed pattern noise and better spatial detection of blood flow changes, although there is still significant noise.
8
Hinsdale, Taylor A. "Laser Speckle Imaging: A Quantitative Tool for Flow Analysis." DigitalCommons@CalPoly, 2014. https://digitalcommons.calpoly.edu/theses/1251.
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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.
9
Lim, Brian. "Modeling ultrasound imaging of red blood cell aggregation in shear flow." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0006/NQ41213.pdf.
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Pierce, Iain Thomas. "MR sequence development for imaging venous blood flow in the leg." Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/10210.
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Deep Vein Thrombosis is a common complication in bed-ridden patients, described as the main cause of preventable hospital deaths in the UK (NICE 2010). Mechanical prophylaxis aims to promote venous flow, either statically with compression stockings, or dynamically with intermittent pneumatic compression or electrical muscle stimulation. Previous studies used ultrasound for venous flow measurements, limited to a single deep vein at a time, and some anatomical MRI for investigating the mechanisms behind these prophylaxes. MRI velocity mapping is used clinically in the arterial system where gating enables data accumulation over multiple cardiac cycles. This thesis describes the development of two real-time MRI spiral velocity mapping sequences for imaging venous blood flow in the leg, where venous flow variability is largely unrelated to the cardiac cycle. Real-time imaging with spiral gradient readouts minimised image duration. A phase-image fitting technique requiring only a velocity-encoded phase image was implemented for acceleration. For in vivo comparison, conventional flow imaging required metronome-guided breathing for a regular venous flow waveform. The long spiral readouts were sensitive to off-resonance and flow artefacts, where some unpublished effects were investigated. The off-resonance associated with deoxygenation of venous blood did not cause notable spiral artefacts, but disrupted the phase-image fitting technique and required correction with a pre-scan. The spiral flow methods demonstrated increased venous blood velocity and flow during application of mechanical compression. Metronome-guided breathing was also applied to vein wall imaging, where it detected wall thickening in patients with Behçet’s disease compared with normal subjects. For the first time, this thesis evaluated real-time MRI spiral velocity mapping of venous blood velocity and flow. The high resolution (1mm) and short image time required caused challenging off-resonance and flow artefacts. With some limitations, real-time spiral flow MRI during operation of compression devices may assist in their optimisation.
11
Milet, Sylvain F. "Visualization and quantification of left heart blood flow by phase encoding magnetic resonance imaging." Thesis, Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/16056.
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Sepehri, Arsalan. "Estimation and reduction of background noise from MRI blood flow images." Thesis, Imperial College London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326246.
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Valdés, Escobar Claudia Patricia. "New laser speckle methods for in vivo blood flow imaging and monitoring." Doctoral thesis, Universitat Politècnica de Catalunya, 2014. http://hdl.handle.net/10803/285015.
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Blood flow and its regulation, as well as hemodynamics in general, are important for the health of tissues and hence the measurement of these quantities has many applications in research and clinical environments. Various optical techniques are attractive for the measurement of blood flow since they are often non- or minimally-invasive, continuous and are relatively inexpensive. During my PhD I have contributed to the monitoring of blood flow in experimental animal models with the construction of a multimodal device, based on laser speckle flowmetry and optical intrinsic signals, capable of measuring superficial microvascular cerebral blood flow, blood oxygenation and blood volume for translational research. This
device was applied in animal models of ischemic stroke and is flexible to be modified and used for other purposes. In doing so, I have developed new experimental methods and image processing protocols that allowed us to perform longitudinal studies where the animal can be removed from the device several times. Furthermore, this device has been used as a tool in a multi-disciplinary study to understand the role of the Mannose-binding lectin protein in reperfusion injury after an ischemic stroke in animal models. This then led to the main contribution of this work which is the development of the speckle contrast optical spectroscopy and tomography, a new non-invasive, optical technique for deep blood flow measurement that paves the way for deeper and three dimensional imaging of blood flow. This new method was first developed from a theoretical perspective. Then it was validated in tissue simulating phantoms and demonstrated to be feasible in measurements on the human arm muscle. Overall, these contributions will allow the development of cost-effective, non-invasive tomographic methods for the measurement of blood flow even in humans.El flujo sanguíneo y su regulación, así como la hemodinámica en general, son parámetros importantes para determinar el estado de salud de los tejidos; por esto, su medición tiene numerosas aplicaciones en los ámbitos clínico y de investigación. Varias técnicas ópticas resultan atractivas para la medición del flujo sanguíneo dado su carácter no invasivo o mínimamente invasivo, continuo y relativamente económico. Durante mi trabajo doctoral he contribuido a la monitorización del flujo sanguíneo, en modelos de experimentación animal, con la construcción de un dispositivo multimodo, basado en la flujometría de speckle láser (laser speckle flowmetry, LSF) y las señales ópticas intrínsicas (optical intrinsic signals, OIS), capaz de medir flujo sanguíneo de la microvasculatura superficial en el cerebro, oxigenación sanguínea y volumen sanguíneo en investigación traslacional. Este dispositivo fue aplicado en modelos animales de infarto cerebral; sin embargo, es flexible y puede ser modificado y utilizado para otros propósitos. Así pues, he desarrollado nuevos métodos experimentales y protocolos de procesamiento de imágenes que nos permitieron llevar a cabo estudios longitudinales, donde los animales pueden ser removidos del dispositivo en repetidas ocasiones. Adicionalmente, este dispositivo fue utilizado como herramienta en un estudio multidisciplinario para entender el papel de la proteína lectina de unión a la manosa (MBL) en las lesiones por isquemia-reperfusión después de un infarto cerebral en modelos animales. Este estudio, dio origen a la mayor contribución de este trabajo, siendo esta el desarrollo de la espectroscopía y tomografía óptica de contraste de speckle; una novedosa técnica óptica, no invasiva para medición de flujo sanguíneo profundo que allana el camino para la obtención de imágenes tridimensionales de flujo sanguíneo más profundo. Este nuevo método, se desarrolló primero desde una perspectiva teórica, y posteriormente se validó en phantoms de tejido biológico, demostrando su factibilidad en mediciones realizadas en el músculo del antebrazo de un paciente. En general, estas contribuciones permitirán el desarrollo de métodos tomográficos, no invasivos y rentables para la medición de flujo sanguíneo, extensibles incluso a seres humanos
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Biglands, John David. "Quanitifying myocardial blood flow using dynamic contrast enhanced cardiac magnetic resonance imaging." Thesis, University of Leeds, 2012. http://etheses.whiterose.ac.uk/3756/.
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The assessment of myocardial perfusion using dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) is a powerful tool for diagnosing myocardial ischaemia due to coronary heart disease, which affects nearly 2.7 million people in the UK and for which there is an effective treatment. Although visual analysis of DCE-MRI data performs well diagnostically, a quantitative estimate of myocardial blood flow (MBF) makes the diagnosis objective and could increase diagnostic performance. Obtaining MBF estimates from DCE-MRI data is a multi-step process requiring: - the localisation of the myocardium and arterial input function (AIF) to generate signal intensity vs. time curves; - the conversion of signal intensity data to contrast agent concentration values; - the application of a perfusion model to generate a quantitative MBF estimate; - the interpretation of MBF estimates to make a diagnostic assessment of myocardial ischaemia. There are a range of approaches for solving each of these problems. The aim of the work presented in this thesis has been to provide clinically relevant evidence for choosing between these approaches. Myocardial localisation contour error tolerance levels are suggested based on simulations using a volunteer dataset. A non-linear signal intensity to contrast agent concentration conversion method is presented and tested using simulations and phantom data. An investigation into the best way to interpret quantitative MBF estimates is then presented. Finally a comparison of four, widely applied, perfusion models is conducted. Where possible, methods have been compared on a sizeable patient dataset in terms of diagnostic performance rather than MBF estimate accuracy. This provides evidence suitable for informing clinical decisions on the best methodology for quantitative perfusion. Such evidence could contribute to a standard methodology for quantitative cardiac MR perfusion. This is necessary for large clinical trials, which are essential before quantitative MBF estimates can be accepted into routine clinical practice.
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Zhou, You. "Fast Algorithm for Simulation of Signals in Medical Ultrasound Blood Flow Imaging." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for elektronikk og telekommunikasjon, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-19522.
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The commonly used simulation method Field II, which is based on the spatial impulse response approach, has excellent accuracy in linear domain. However the computational time can be up to many days for one simulation. One of the solutions to this problem is a convolution-based methodology called COLE. It is much faster than Field II and has very good approximation. It generates the data by reducing multi-dimensional convolution model to multiple single-dimensional convolutions. This thesis is about implementing COLE on the FieldSim 3 platform and using it for blood flow imaging. This platform is written in MATLAB with object-oriented programming and it is now under development at department of circulation and medical imaging. Both Field II and real scanner have been used to compare with COLE. The simulated phantom for both simulators was a straight tube with scatterers moving inside, whereas a string phantom was used to get the data from the scanner. The computational time of COLE with 2D Doppler mode scan in FieldSim 3 achieved 85 times faster than Field II. The plotted PW Doppler spectra and the 2D power spectra showed that the velocity resolutions of both simulators were at the same level. COLE had higher noise floor than Field II and scanner in Doppler mode scan. COLE had relatively high sampling frequency requirement compared with Field II. If the sampling frequency was not high enough, COLE would produce side lobes in the PW Doppler spectra.
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Gallichan, Daniel. "Measuring cerebral blood flow using arterial spin labelling with magnetic resonance imaging." Thesis, University of Oxford, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.442955.
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Xie, Jingyi. "Quantitative measurement of regional cerebral blood flow with arterial spin labelling imaging." Thesis, University of Oxford, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.504384.
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Okell, Thomas William. "Assessment of collateral blood flow in the brain using magnetic resonance imaging." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:7e63bcf2-22bf-49e5-81ec-1644217605ae.
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Collateral blood flow is the compensatory flow of blood to the tissue through secondary channels when the primary channel is compromised. It is of vital importance in cerebrovascular disease where collateral flow can maintain large regions of brain tissue which would otherwise have suffered ischaemic damage. Traditional x-ray based techniques for visualising collateral flow are invasive and carry risks to the patient. In this thesis novel magnetic resonance imaging techniques for performing vessel-selective labelling of brain feeding arteries are explored and developed to reveal the source and extent of collateral flow in the brain non-invasively and without the use of contrast agents. Vessel-encoded pseudo-continuous arterial spin labelling (VEPCASL) allows the selective labelling of blood water in different combinations of brain feeding arteries that can be combined in post-processing to yield vascular territory maps. The mechanism of VEPCASL was elucidated and optimised through simulations of the Bloch equations and phantom experiments, including its sensitivity to sequence parameters, blood velocity and off-resonance effects. An implementation of the VEPCASL pulse sequence using an echo-planar imaging (EPI) readout was applied in healthy volunteers to enable optimisation of the post-labelling delay and choice of labelling plane position. Improvements to the signal-to-noise ratio (SNR) and motion-sensitivity were made through the addition of background suppression pulses and a partial-Fourier scheme. Experiments using a three-dimensional gradient and spin echo (3D-GRASE) readout were somewhat compromised by significant blurring in the slice direction, but showed potential for future work with a high SNR and reduced dropout artefacts. The VEPCASL preparation was also applied to a dynamic 2D angiographic readout, allowing direct visualisation of collateral blood flow in the brain as well as a morphological and functional assessment of the major cerebral arteries. The application of a balanced steady-state free precession (bSSFP) readout significantly increased the acquisition efficiency, allowing the generation of dynamic 3D vessel-selective angiograms. A theoretical model of the dynamic angiographic signal was also derived, allowing quantification of blood flow through specified vessels, providing a significant advantage over qualitative x-ray based methods. Finally, these methods were applied to a number of patient groups, including those with vertebro-basilar disease, carotid stenosis and arteriovenous malformation. These preliminary studies demonstrate that useful clinical information regarding collateral blood flow can be obtained with these techniques.
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Valdés, Escobar Claudia Patricia. "New laser speckle methods for in vivo blood flow imaging and monitoring." Thesis, Aix-Marseille, 2014. http://www.theses.fr/2014AIXM4367/document.
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Le débit sanguin et sa régulation sont des indicateurs importants de la santé des tissus. Leur mesure a de nombreuses applications en recherche fondamentale et clinique. Certaines techniques optiques constituent un moyen intéressant pour la mesure du débit sanguin, car en général elles sont peu invasives et relativement abordables car elles utilisent des systèmes d'illumination continus. Pendant ma thèse, j'ai contribué au développement de techniques de suivi de la circulation sanguine dans des modèles animaux avec la construction d'un dispositif multimodal basé sur la fluxmétrie laser et sur l'imagerie des signaux optiques intrinsèques, capable de mesurer les paramètre hémodynamiques microvasculaire au niveau superficiel du cerveau. Ce dispositif, testé sur des modèles animaux d'accident vasculaire cérébral, est adaptable et peut être utilisé à d'autres fins. En parallèle, j'ai mis au point des nouvelles méthodes expérimentales et des protocoles de traitement d'images qui ont permis de réaliser des études longitudinales. En outre, ce dispositif a été utilisé dans une étude multidisciplinaire pour comprendre le rôle d'une protéine impliquée dans le cas de lésions de reperfusion après un accident vasculaire cérébral ischémique dans des modèles animaux. Ma contribution majeure réside dans le développement de l'imagerie de contraste de speckle spectroscopique et tomographique, nouvelle technique d'imagerie 3D non invasive pour la mesure du débit sanguin en profondeur. Dans l'ensemble, ces contributions permettront le développement de méthodes tomographiques non invasives rentables pour la mesure du débit sanguin chez l'hommeBlood flow and its regulation are important for the health of tissues and its measurement has many applications in research and clinical environments. Optical techniques are often attractive for the non- or minimally-invasive, continuous and relatively inexpensive measurement of blood flow. This work contributes to the monitoring of blood flow in translational research with the construction of a multimodal device, based on laser speckle flowmetry and optical intrinsic signals, capable of measuring superficial microvascular cerebral blood flow, blood oxygenation and blood volume. This device was applied in animal models of ischemic stroke and is flexible to be modified and used for other purposes. In doing so, I have developed new experimental methods and image processing protocols that allowed us to perform longitudinal studies where the animal can be removed from the device several times. This device has also been used to elucidate the role of the Mannose-binding lectin protein in reperfusion injury after an ischemic stroke in animal models. This led to the main contribution of this work: the development of the speckle contrast optical spectroscopy and tomography, a new non-invasive, optical technique for deep blood flow measurement that paves the way for deeper and three dimensional imaging of blood flow. This new method was first developed from a theoretical perspective. Then it was validated in tissue simulating phantoms and demonstrated to be feasible in measurements on the human arm muscle. Overall, these contributions will allow the development of cost-effective, non-invasive tomographic methods for the measurement of blood flow even in humans
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Irwin, Daniel. "MULTIMODAL NONCONTACT DIFFUSE OPTICAL REFLECTANCE IMAGING OF BLOOD FLOW AND FLUORESCENCE CONTRASTS." UKnowledge, 2018. https://uknowledge.uky.edu/cbme_etds/50.
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In this study we design a succession of three increasingly adept diffuse optical devices towards the simultaneous 3D imaging of blood flow and fluorescence contrasts in relatively deep tissues. These metrics together can provide future insights into the relationship between blood flow distributions and fluorescent or fluorescently tagged agents. A noncontact diffuse correlation tomography (ncDCT) device was firstly developed to recover flow by mechanically scanning a lens-based apparatus across the sample. The novel flow reconstruction technique and measuring boundary curvature were advanced in tandem. The establishment of CCD camera detection with a high sampling density and flow recovery by speckle contrast followed with the next instrument, termed speckle contrast diffuse correlation tomography (scDCT). In scDCT, an optical switch sequenced coherent near-infrared light into contact-based source fibers around the sample surface. A fully noncontact reflectance mode device finalized improvements by combining noncontact scDCT (nc_scDCT) and diffuse fluorescence tomography (DFT) techniques. In the combined device, a galvo-mirror directed polarized light to the sample surface. Filters and a cross polarizer in stackable tubes promoted extracting flow indices, absorption coefficients, and fluorescence concentrations (indocyanine green, ICG). The scDCT instrumentation was validated through detection of a cubical solid tissue-like phantom heterogeneity beneath a liquid phantom (background) surface where recovery of its center and dimensions agreed with the known values. The combined nc_scDCT/DFT identified both a cubical solid phantom and a tube of stepwise varying ICG concentration (absorption and fluorescence contrast). The tube imaged by nc_scDCT/DFT exhibited expected trends in absorption and fluorescence. The tube shape, orientation, and localization were recovered in general agreement with actuality. The flow heterogeneity localization was successfully extracted and its average relative flow values in agreement with previous studies. Increasing ICG concentrations induced notable disturbances in the tube region (≥ 0.25 μM/1 μM for 785 nm/830 nm) suggesting the graduating absorption (320% increase at 785 nm) introduced errors. We observe that 830 nm is lower in the ICG absorption spectrum and the correspondingly measured flow encountered less influence than 785 nm. From these results we anticipate the best practice in future studies to be utilization of a laser source with wavelength in a low region of the ICG absorption spectrum (e.g., 830 nm) or to only monitor flow prior to ICG injection or post-clearance. In addition, ncDCT was initially tested in a mouse tumor model to examine tumor size and averaged flow changes over a four-day interval. The next steps in forwarding the combined device development include the straightforward automation of data acquisition and filter rotation and applying it to in vivo tumor studies. These animal/clinical models may seek information such as simultaneous detection of tumor flow, fluorescence, and absorption contrasts or analyzing the relationship between variably sized fluorescently tagged nanoparticles and their tumor deposition relationship to flow distributions.
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Summers, Paul Eugene. "Quantitative flow by magnetic resonance phase mapping." Thesis, King's College London (University of London), 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267482.
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Cheung, Ka-hei, and 張嘉熹. "Adaptive clutter filter design for micro-ultrasound color flow imagingof small blood vessels." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B45517873.
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Kolthammer, Jeffrey A. "Quantitative Positron Emission Tomography for Estimation of Absolute Myocardial Blood Flow." Case Western Reserve University School of Graduate Studies / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=case1365007300.
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Henderson, Elizabeth. "Measurement of blood flow, blood volume and capillary permeability in breast tumours using contrast-enhanced magnetic resonance imaging." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0020/NQ58134.pdf.
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Correia, Mafalda Filipa Rodrigues. "From 2D to 3D cardiovascular ultrafast ultrasound imaging : new insights in shear wave elastography and blood flow imaging." Thesis, Sorbonne Paris Cité, 2016. http://www.theses.fr/2016USPCC158.
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Ces travaux de thèse portent sur le développement de nouvelles modalités d’imagerie cardiovasculaire basé sur l’utilisation de l'imagerie ultrarapide 2D et 3D. Les modalités d’imagerie développées dans cette thèse appartiennent au domaine de de l’élastographie par onde de cisaillement et de l'imagerie Doppler des flux sanguins.Dans un premier temps, la technique de l’élastographie par onde de cisaillement du myocarde a été développée pour les applications cliniques. Une approche d'imagerie non-linéaire a été utilisée pour améliorer l’estimation de vitesse des ondes de cisaillement (ou la rigidité des tissus cardiaques) de manière non invasive et localisée. La validation de cette nouvelle approche de « l’imagerie par sommation cohérente harmonique ultrarapide » a été réalisée in vitro et la faisabilité in vivo a été testée chez l’humain. Dans un second temps, nous avons utilisé cette technique sur des patients lors de deux essais cliniques, chacun ciblant une population différente (adultes et enfants). Nous avons étudié la possibilité d’évaluer quantitativement la rigidité des tissus cardiaques par élastographie chez des volontaires sains, ainsi que chez des malades souffrant de cardiomyopathie hypertrophique. Les résultats ont montré que l’élastographie pourrait devenir un outil d'imagerie pertinent et robuste pour évaluer la rigidité du muscle cardiaque en pratique clinique. Par ailleurs, nous avons également développé une nouvelle approche appelée « imagerie de tenseur élastique 3-D » pour mesurer quantitativement les propriétés élastiques des tissus anisotropes comme le myocarde. Ces techniques ont été testées in vitro sur des modèles de de gels isotropes transverses. La faisabilité in vivo de l’élastographie par onde cisaillement à trois-dimensions a été également évaluée sur un muscle squelettique humain.D'autre part, nous avons développé une toute nouvelle modalité d’imagerie ultrasonore des flux coronariens basée sur l’imagerie Doppler ultrarapide. Cette technique nous a permis d'imager la circulation coronarienne avec une sensibilité élevée, grâce notamment au développement d’un nouveau filtre adaptatif permettant de supprimer le signal du myocarde en mouvement, basé sur la décomposition en valeurs singulières (SVD). Des expériences à thorax ouvert chez le porc ont permis d'évaluer et de valider notre technique et les résultats ont montré que la circulation coronaire intramurale, peut être évaluée sur des vaisseaux de diamètres allant jusqu’à 100 µm. La faisabilité sur l’homme a été démontrée chez l’enfant en imagerie clinique transthoracique.Enfin, nous avons développé une nouvelle approche d’imagerie des flux sanguins, « l’imagerie ultrarapide 3-D des flux», une nouvelle technique d'imagerie quantitative des flux. Nous avons démontré que cette technique permet d’évaluer le débit volumétrique artériel directement en un seul battement cardiaque, indépendamment de l'utilisateur. Cette technique a été mise en place à l'aide d'une sonde matricielle 2-D et d’un prototype d’échographe ultrarapide 3-D développé au sein du laboratoire. Nous avons évalué et validé notre technique in vitro sur des fantômes artériels, et la faisabilité in vivo a été démontrée sur des artères carotides humainesThis thesis was focused on the development of novel cardiovascular imaging applications based on 2-D and 3-D ultrafast ultrasound imaging. More specifically, new technical and clinical developments of myocardial shear wave elastography and ultrafast blood flow imaging are presented in this manuscript.At first, myocardial shear wave elastography was developed for transthoracic imaging and improved by a non-linear imaging approach to non-invasively and locally assess shear wave velocity measurements, and consequently tissue stiffness in the context of cardiac imaging. This novel imaging approach (Ultrafast Harmonic Coherent Compounding) was tested and validated in-vitro and the in vivo feasibility was performed in humans for biomechanical evaluation of the cardiac muscle wall, the myocardium. Then, we have translated shear wave elastography to the clinical practice within two clinical trials, each one with a different population (adults and children). In both clinical trials, we have studied the capability of shear wave elastography to assess quantitatively myocardial stiffness in healthy volunteers and in patients suffering from hypertrophic cardiomyopathy. The results in the adult population indicated that shear wave elastography may become an effective imaging tool to assess cardiac muscle stiffness in clinical practice and help the characterization of hypertrophic cardiomyopathy. Likewise, we have also translated Shear Wave Elastography into four-dimensions and we have developed a new approach to map tissue elastic anisotropy in 3-D. 3-D Elastic Tensor Imaging allowed us to estimate quantitatively in a single acquisition the elastic properties of fibrous tissues. This technique was tested and validated in vitro in transverse isotropic models. The in-vivo feasibility of 3D elastic tensor imaging was also assessed in a human skeletal muscle.In parallel, we have developed a novel imaging technique for the non-invasive and non-radiative imaging of coronary circulation using ultrafast Doppler. This approach allowed us to image blood flow of the coronary circulation with high sensitivity. A new adaptive filter based on the singular value decomposition was used to remove the clutter signal of moving tissues. Open-chest swine experiments allowed to evaluate and validate this technique and results have shown that intramural coronary circulation, with diameters up to 100 µm, could be assessed. The in-vivo transthoracic feasibility was also demonstrated in humans in pediatric cardiology.Finally, we have developed a novel imaging modality to map quantitatively the blood flow in 3-D: 3-D ultrafast ultrasound flow imaging. We demonstrated that 3-D ultrafast ultrasound flow imaging can assess non-invasively, user-independently and directly volumetric flow rates in large arteries within a single heartbeat. We have evaluated and validated our technique in vitro in arterial phantoms using a 2-D matrix-array probe and a customized, programmable research 3-D ultrafast ultrasound system, and the in-vivo feasibility was demonstrated in human carotid arteries
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Kardan, Ahmad A. "An ultrasonic system for intravascular measurement and visualisation of anatomical structures and blood flow." Thesis, Imperial College London, 1991. http://hdl.handle.net/10044/1/46857.
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Koirala, Nischal. "Access Blood Flow Measurement Using Angiography." Cleveland State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=csu153796812445051.
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Norden, Andrew D. "Use of SPECT Difference Imaging to Assess Subcortical Blood Flow Changes During Epileptic Seizures." Yale University, 2003. http://ymtdl.med.yale.edu/theses/available/etd-02112003-133913/.
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Seizures are thought to arise primarily from the cerebral cortex. However, the propagation and behavioral manifestations of seizures involve a network of both cortical and subcortical structures. The medial thalamus and upper brainstem reticular formation are crucial areas for the maintenance of normal consciousness. Bilateral involvement of these structures may be responsible for loss of consciousness during partial seizures. Therefore, we sought to investigate the role of the medial thalamus and brainstem in seizures. We performed SPECT ictal-interictal difference imaging co-registered with high-resolution MRI scans to localize regions of cerebral blood flow changes in patients undergoing inpatient monitoring for epilepsy. Ictal-interictal SPECT scans from 43 seizures in 40 patients were analyzed. The medial thalami showed SPECT difference imaging changes of >20% in 18 patients. Of patients with medial thalamic changes, the majority (13 of 18) had seizure onset in the temporal lobe, while only 1 had confirmed onset in extratemporal structures, and the remainder were non-localized. In contrast, in the 22 patients without >20% SPECT changes in the medial thalami, 6 had extratemporal onset, 6 had temporal onset, and the remainder were non-localized. In patients with temporal lobe seizures, the side of greater medial thalamic and brainstem reticular formation involvement was strongly related to SPECT injection timing such that there was a sequential pattern of ipsilateral followed by contralateral changes. Brainstem structures showed >20% SPECT changes in 27 of 43 seizures with no clear relation to temporal or extratemporal onset. We conclude that the medial thalamus is preferentially involved in seizures arising from the temporal lobes, possibly reflecting the strong connections between limbic temporal structures and the medial thalamus. Sequential involvement of ipsilateral followed by contralateral structures in the medial thalamus and upper brainstem may explain how seizures produce peri-ictal loss of consciousness despite incomplete involvement of the cerebral cortex.
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Ollenberger, Glenn P. "Imaging of cardiac output and regional cerebral blood flow during the mammalian dive response." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ37904.pdf.
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Wallin, Ashley Kay. "Renal Arterial Blood Flow Quantification by Breath-held Phase-velocity Encoded MRI." Thesis, Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/4982.
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Autosomal dominant polycystic disease (ADPKD) is the most common hereditary renal disease and is characterized by renal cyst growth and enlargement. Hypertension occurs early when renal function is normal and is characterized by decreased renal blood flow. Accordingly, the measurement of blood flow in the renal arteries can be a valuable tool in evaluating disease progression. In studies performed in conjunction with this work, blood flow was measured through the renal arteries using magnetic resonance imaging (MRI). In order to validate these in vivo measurements, a vascular phantom was created using polyvinyl alcohol (PVA) and also scanned using MRI under controlled steady flow conditions. Ranges of vessel diameters and flow velocities were used to simulate actual flow in a normal and diseased population of adults and children.
With the vessel diameters studied in this experiment, minimization of field of view and an increase in spatial resolution is important in obtaining accurate data. However, a significant difference does not exist between the results when using the 160 or 200 mm FOV. An increase in the number of phase encodings provides improved results, although an increase in image acquisition time is observed. Velocity-encoding in all three orthogonal directions does not improve image data. This method of using MRI to measure flow through a vessel is shown to be both accurate and reproducible, and the protocol providing the most correct results is prescribed.
Breath-hold phase-velocity encoded MRI proves to be an accurate and reproducible technique in capturing flow and has the potential to be used for the purpose of observing hemodynamic changes in the renal arteries with the progression of ADPKD.
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Eriksson, Jonatan, Ann F. Bolger, Tino Ebbers, and Carl-Johan Carlhäll. "Four-dimensional blood flow-specific markers of LV dysfunction in dilated cardiomyopathy." Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-87616.
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Aims : Patients with mild heart failure (HF) who are clinically compensated may have normal left ventricular (LV) stroke volume (SV). Despite this, altered intra-ventricular flow patterns have been recognized in these subjects. We hypothesized that, compared with normal LVs, flow in myopathic LVs would demonstrate a smaller proportion of inflow volume passing directly to ejection and diminished the end-diastolic preservation of the inflow kinetic energy (KE). Methods and results : In 10 patients with dilated cardiomyopathy (DCM) (49 ± 14 years, six females) and 10 healthy subjects (44 ± 17 years, four females), four-dimensional MRI velocity and morphological data were acquired. A previously validated method was used to separate the LV end-diastolic volume (EDV) into four flow components based on the blood's locations at the beginning and end of the cardiac cycle. KE was calculated over the cardiac cycle for each component. The EDV was larger (P = 0.021) and the ejection fraction smaller (P < 0.001) in DCM compared with healthy subjects; the SV was equivalent (DCM: 77 ± 19, healthy: 79 ± 16 mL). The proportion of the total LV inflow that passed directly to ejection was smaller in DCM (P = 0.000), but the end-diastolic KE/mL of the direct flow was not different in the two groups (NS). Conclusion : Despite equivalent LVSVs, HF patients with mild LV remodelling demonstrate altered diastolic flow routes through the LV and impaired preservation of inflow KE at pre-systole compared with healthy subjects. These unique flow-specific changes in the flow route and energetics are detectable despite clinical compensation, and may prove useful as subclinical markers of LV dysfunction.
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Guenet, Frederique S. A. "Quantification of valvular regurgitation by proximal isovelocity surface area and magnetic resonance imaging." Thesis, Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/11207.
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Kumar, Hemant. "Software analytical tool for assessing cardiac blood flow parameters /." View thesis, 2001. http://library.uws.edu.au/adt-NUWS/public/adt-NUWS20030724.122149/index.html.
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Baeza, Ortega José Antonio. "Combined Visualization of Intracardiac Blood Flow and Wall Motion Assessed by MRI." Thesis, Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-75881.
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MRI is a well known and widely spread technique to characterize cardiac pathologies due to its high spatial resolution, its accessibility and its adjustable contrast among soft tissues. In attempt to close the gap between blood flow, myocardial movement and the cardiac fucntion, researching in the MRI field addresses the quantification of some of the most relevant blood and myocardial parameters. During this proyect a new tool that allows reading, postprocessing, quantifying and visualizing 2D motion sense MR data has been developed. In order to analyze intracardiac blood flow and wall motion, the new tool quantifies velocity, turbulent kinetic energy, pressure and strain. In the results section the final tool is presented, describing the visualization modes, which represent the quantified parameters both individually and combined; and detailing auxiliary tool features as masking, thresholding, zooming, and cursors. Finally, thecnical aspects as the convenience of two dimensional examinations to create compact tools, and the challenges of masking as part of the relative pressure calculation, among others, are discussed; ending up with the proposal of some future developments.
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Shi, Yulu. "Cerebral blood flow and intracranial pulsatility in cerebral small vessel disease." Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/29625.
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Cerebral small vessel disease (SVD) is associated with increased risks of stroke and dementia, however the mechanisms remain unclear. Low cerebral blood flow (CBF) has long been suggested and accepted, but clinical evidence is conflicting. On the other hand, growing evidence suggests that increased intracranial pulsatility due to vascular stiffening might be an alternative mechanism. Pulse-gated phase-contrast MRI is an imaging technique that allows measuring of CBF contemporaneously with pulsatility in multiple vessels and cerebrospinal fluid (CSF) spaces. The overall aim of this thesis was to provide an overview of existing clinical evidence on both hypotheses, to test the reproducibility of CBF and pulsatility measures in phase-contrast MRI, and to explore the relationship between CBF and intracranial pulsatility and SVD features in a group of patients with minor stroke and SVD changes on brain imaging. I first systematically reviewed and meta-analysed clinical studies that have assessed CBF or intracranial pulsatility in SVD patients. There were 38 studies (n=4006) on CBF and 27 (n=3356) on intracranial pulsatility. Most were cross-sectional, and longitudinal studies were scarce. There were large heterogeneities in patient characteristics and indices used particularly for measuring and calculating pulsatility. Methods to reduce bias such as blinding and the expertise of structural image readers were generally poorly reported, and many studies did not account for the impact of confounding factors (e.g. age, vascular risk factors and disease severity) on CBF or pulsatility. Evidence for falling CBF predating SVD was not supported by longitudinal studies; high pulsatility in one large artery such as internal carotid arteries (ICA) or middle cerebral arteries might be related to SVD, but studies that measured arteries, veins and CSF in the same patients were very limited and the reliability of some pulsatility measures, especially in CSF, needs to be tested. In order to test the reproducibility of the CBF and intracranial pulsatility measures, I repeated 2D phase-contrast MRI scans of vessels and CSF on healthy volunteers during two visits. I also compared the ICA pulsatility index derived from the MRI flow waveform to that from the Doppler ultrasound velocity waveform in patients with minor stroke and SVD features. In 10 heathy volunteers (age 35.2±9.78 years), the reproducibility of CBF and vascular pulsatility indices was good, with within-subject coefficients of variability (CV) less than 10%; whereas CSF flow and pulsatility measures were generally less reproducible (CV > 20%). In 56 patients (age 67.8±8.27 years), the ICA pulsatility indices in Doppler ultrasound and MRI were acceptably well-correlated (r=0.5, p < 0.001) considering the differences in the two techniques. We carried out a cross-sectional study aiming to recruit 60 patients with minor stroke and SVD features. We measured CBF and intracranial pulsatility using phase-contrast MRI, as well as aortic augmentation index (AIx) using a SphygmoCor device. I first investigated the relationship between intracranial measures, and systemic blood pressure or aortic AIx, and then focused on how the intracranial haemodynamic measures related to two main SVD features (white matter hyperintensities (WMH) and perivascular spaces (PVS)). We obtained usable data from 56/60 patients (age 67.8±8.27 years), reflecting a range of SVD burdens. After the adjustment for age, gender, and history of hypertension, higher pulsatility in the venous sinuses was associated with lower diastolic blood pressure and lower mean arterial pressure (e.g. diastolic blood pressure on straight sinus pulsatility index (PI): β=-0.005, P=0.029), but not with aortic AIx. Higher aortic AIx was associated with low ICA PI (β=-0.011, P=0.040). Increased pulsatility in the venous sinuses, not low CBF, was associated with greater WMH volume (e.g. superior sagittal sinus PI: β=1.29, P=0.005) and more basal ganglia PVS (e.g. odds ratio=1.379 per 0.1 increase in superior sagittal sinus PI) after the adjustment for age, gender and blood pressure. The thesis is the first to summarise the literature on CBF and intracranial pulsatility in SVD patients, addressed the major limitations of current clinical studies of SVD, and also assessed CBF and intracranial pulsatility contemporaneously in well-characterised patients with SVD features. The overall results of the thesis challenge the traditional hypothesis of the cause and effect between low CBF and SVD, and suggest that increased cerebrovascular pulsatility, which might be due to intrinsic cerebral small vessel pathologies rather than just aortic stiffness, is important for SVD. More importantly, this pilot study also provides a reliable methodology for measuring intracranial pulsatility using phase-contrast MRI for future longitudinal or larger multicentre studies, and shows that intracranial pulsatility could be used as a secondary outcome in clinical trials of SVD. However, future research is required to elucidate the implication of venous pulsatility and to fully explore the passage of pulse wave transmission in the brain. Overall, this thesis advances knowledge and suggest potential targets for future SVD studies in terms of mechanisms, prevention and treatment.
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Prowle, John Richard. "Renal blood flow and the pathophysiology of acute kidney injury." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.607649.
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Wilson, Daniel Jonathan. "The measurement of abnormal and normal blood flow to the liver using magnetic resonance imaging." Thesis, University of Leeds, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.505062.
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The liver is a unique organ having both an arterial and venous blood supply. The arterial supply is via the hepatic artery and the venous supply is via the portal vein. In a healthy liver the fraction of blood that is delivered via the hepatic artery is approximately 20%. This fraction is called the hepatic arterial fraction. In a variety of liver diseases including cirrhosis and when there are colorectal metastases present in the liver this fraction increases. The measurement of this fraction has been attempted using Doppler ultrasound, radioisotopes, computed tomography and magnetic resonance imaging (MRI) but despite initial promising results the method has not proven to be reproducible at different centres.
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Essex, Timothy John Hudson. "The development and evaluation of a scanning laser Doppler instrument for imaging skin blood flow." Thesis, Northumbria University, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357147.
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Santelli, Claudio. "Accelerating multi-dimensional magnetic resonance imaging of blood flow and turbulence in the cardiovascular system." Thesis, King's College London (University of London), 2015. http://kclpure.kcl.ac.uk/portal/en/theses/accelerating-multidimensional-magnetic-resonance-imaging-of-blood-flow-and-turbulence-in-the-cardiovascular-system(8a415f79-2e07-48fd-ba14-13eab607da22).html.
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Disturbed hemodynamic conditions are often related to pathologies of the cardiovascular system. Phase‐contrast Magnetic Resonance Imaging (MRI) provides a non‐invasive technique for the assessment of time‐resolved blood velocity vector fields within arbitrary imaging volumes. Besides velocity vector field information, parameters related to turbulence can be calculated with advanced multi‐point velocity encoding schemes. However, long scan times are currently the main barrier for the acceptance of the method in a clinical setting. The following work presents data‐driven MRI reconstruction algorithms for undersampled measurements with the focus on accurate flow quantification and visualization. An extension of an auto‐calibrated parallel imaging reconstruction framework for arbitrary kspace trajectories is proposed. The exploitation of temporal correlations as present in timeresolved data demonstrates further advances of scan time reduction when assessing mean velocity and turbulent kinetic energy. While most prior knowledge imposed in advanced MR image reconstruction is designed to work on magnitude images or assumes smooth background phase behavior, dedicated provisions are required for image reconstruction of phase‐contrast MRI data. To this end, it is proposed to incorporate the divergence‐free condition of blood flow into a separate magnitude and phase reconstruction framework for improving the accuracy of image reconstruction of blood velocity vector fields. To address respiratory motion artifacts, retrospective non‐rigid respiratory motion correction incorporated into an iterative parallel imaging reconstruction algorithm is proposed. Furthermore, optimized k‐t sampling patterns are derived for combined parallel imaging‐ and compressed sensing‐based scan acceleration. Finally, the dynamic parallel imaging technique is applied to study blood flow and turbulence patterns in a relevant patient population with congenital heart disease.
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Ekroll, Ingvild Kinn. "Ultrasound imaging of blood flow based on high frame rate acquisition and adaptive signal processing." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for sirkulasjon og bildediagnostikk, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-20512.
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Ultrasound imaging of blood flow is in widespread use for assessment of atherosclerotic disease. Imaging of the carotid arteries is of special interest, as blood clots from atherosclerotic plaques may follow the blood stream to the brain with fatal consequences. Color flow imaging and PW Doppler are important tools during patient examination, providing a map of the mean velocities in an image region and the full velocity spectrum in a small region of interest respectively. However they both suffer from limitations which may hamper patient diagnostics. Recent technological advances have enabled an increased acquisition rate of ultrasound images, providing possibilities for further improvement in robustness and accuracy of color flow and PW Doppler imaging. Based on these advances, we aimed to utilize the high acquisition rate to enable robust vector Doppler imaging, where both velocity magnitude and direction is estimated. Additionally, we wanted to incorporate information from several parallel receive beams in spectral Doppler, which is currently limited to velocity estimation in a limited region of a single beam. Two limitations in conventional PW Doppler are especially considered, namely the trade-off between temporal and spectral resolution, and the increased spectral broadening in situations of high velocity or large beam-to-flow angles. By utilizing information from several parallel receive beams, we show that by applying adaptive spectral estimation techniques, it is possible to obtain high quality PW Doppler spectra from ensembles similar to those found in conventional color flow imaging. A new method to limit spectral broadening is also presented, and we show spectra with improved resolution and signal-to-noise ratio for a large span in beam-to-flow angles. Plane wave vector Doppler imaging was investigated using both realistic simulations of flow in a (diseased) carotid artery bifurcation, and in vivo studies. It was found that the plane wave approach could provide robust vector velocity estimates at frame rates significantly higher than what is found in conventional blood flow imaging. The technique was implemented in a research ultrasound system, and a feasibility study was performed in patients with carotid artery disease. Promising results were found, showing an increased velocity span and the successful capture of complex flow patterns. All together, the proposed techniques may provide more efficient clinical tools for vascular imaging, as well as quantitative information for research into new markers for cardiovascular disease.
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Li, Longchuan. "Numerical and experimental study of three imaging advancements in phase contrast magnetic resonance imaging." Birmingham, Ala. : University of Alabama at Birmingham, 2007. http://www.mhsl.uab.edu/dt/2007p/li.pdf.
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Jackson, Joel R. "Ultrasonic imaging of the structure and elasticity of the carotid bifurcation." Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/15718.
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Barmby, David Stuart. "Non-invasive quantification of myocardial blood flow by cardiac magnetic resonance imaging : validation of quantified myocardial perfusion imaging with intracoronary pressure/flow measurement in coronary heart disease." Thesis, University of Leeds, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.426772.
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Golster, Helena. "Regulation of microvascular blood flow : a clinical and experimental study based on laser Doppler perfusion imaging /." Linköping : Univ, 2001. http://www.bibl.liu.se/liupubl/disp/disp2001/med683s.pdf.
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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.
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Saber, Nikoo Rezazadeh. "CFD modelling of blood flow in the human left ventricle based on magnetic resonance imaging data." Thesis, Imperial College London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390806.
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Eghbali, Ladan. "The impact of defective ultrasound transducers on the evaluation results of ultrasound imaging of blood flow." Thesis, KTH, Skolan för teknik och hälsa (STH), 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-154830.
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Following X-Ray, Ultrasound is now the most common of all the medical imaging technologies specifically in obstetrics and cardiology. Plus that the ultrasound hazards perceived to be insignificant compared with X-rays. Considering the fact that the study of cardiovascular diseases, blood flow patterns and the fetal development is essential for human life, the accuracy and proper functioning of ultrasonic systems is of great importance. Hence quality control of ultrasonic transducers is necessary. In this thesis, a system to standardize the acceptance criteria for quality control of ultrasonic transducers is described. On this ground a study on ultrasound images conducted to compare and evaluate the quality resulted from different types of transducers in different conditions, i.e. defective or functional. A clinical study was also carried out to evaluate our hypothesis in real cases at department of Cardiology and department of genecology. Results from this study show that the perception of quality is somewhat subjective and clinical studies are time-consuming. But quality factors such as the ability to accurately identify anatomical structure and functional capabilities are of great importance and help.
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Eriksson, Jonatan. "Quantification of 4D Left Ventricular Blood Flow in Health and Disease." Doctoral thesis, Linköpings universitet, Avdelningen för kardiovaskulär medicin, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-98786.
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The main function of the heart is to pump blood throughout the cardiovascular system by generating pressure differences created through volume changes. Although the main purpose of the heart and vessels is to lead the flowing blood throughout the body, clinical assessments of cardiac function are usually based on morphology, approximating the flow features by viewing the motion of the myocardium and vessels. Measurement of three-directional, three-dimensional and time-resolved velocity (4D Flow) data is feasible using magnetic resonance (MR). The focus of this thesis is the development and application of methods that facilitate the analysis of larger groups of data in order to increase our understanding of intracardiac flow patterns and take the 4D flow technique closer to the clinical setting. In the first studies underlying this thesis, a pathline based method for analysis of intra ventricular blood flow patterns has been implemented and applied. A pathline is integrated from the velocity data and shows the path an imaginary massless particle would take through the data volume. This method separates the end-diastolic volume (EDV) into four functional components, based on the position for each individual pathline at end-diastole (ED) and end-systole (ES). This approach enables tracking of the full EDV over one cardiac cycle and facilitates calculation of parameters such as e.g. volumes and kinetic energy (KE). Besides blood flow, pressure plays an important role in the cardiac dynamics. In order to study this parameter in the left ventricle, the relative pressure field was computed using the pressure Poisson equation. A comprehensive presentation of the pressure data was obtained dividing the LV blood pool into 17 pie-shaped segments based on a modification of the standard seventeen segment model. Further insight into intracardiac blood flow dynamics was obtained by studying the turbulent kinetic energy (TKE) in the LV. The methods were applied to data from a group of healthy subjects and patients with dilated cardiomyopathy (DCM). DCM is a pathological state where the cardiac function is impaired and the left ventricle or both ventricles are dilated. The validation study of the flow analysis method showed that a reliable user friendly tool for intra ventricular blood flow analysis was obtained. The application of this tool also showed that roughly one third of the blood that enters the LV, directly leaves the LV again in the same heart beat. The distribution of the four LV EDV components was altered in the DCM group as compared to the healthy group; the component that enters and leaves the LV during one cardiac cycle (Direct Flow) was significantly larger in the healthy subjects. Furthermore, when the kinetic energy was normalized by the volume for each component, at time of ED, the Direct Flow had the highest values in the healthy subjects. In the DCM group, however, the Retained Inflow and Delayed Ejection Flow had higher values. The relative pressure field showed to be highly heterogeneous, in the healthy heart. During diastole the predominate pressure differences in the LV occur along the long axis from base to apex. The distribution and variability of 3D pressure fields differ between early and late diastolic filling phases, but common to both phases is a relatively lower pressure in the outflow segment. In the normal LV, TKE values are low. The highest TKE values can be seen during early diastole and are regionally distributed near the basal LV regions. In contrast, in a heterogeneous group of DCM patients, total diastolic and late diastolic TKE values are higher than in normals, and increase with the LV volume. In conclusion, in this thesis, methods for analysis of multidirectional intra cardiac velocity data have been obtained. These methods allow assessment of data quality, intra cardiac blood flow patterns, relative pressure fields, and TKE. Using these methods, new insights have been obtained in intra cardiac blood flow dynamics in health and disease. The work underlying this thesis facilitates assessment of data from a larger population of healthy subjects and patients, thus bringing the 4D Flow MRI technique closer to the clinical setting.
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Young, Anthony M. "Investigation of Laser Speckle Contrast Imaging's Sensitivity to Flow." Miami University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=miami153256524246362.
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Kumar, Hemant. "Software analytical tool for assessing cardiac blood flow parameters." Thesis, View thesis, 2001. http://handle.uws.edu.au:8081/1959.7/392.
Full textAbstract:
Introduction of Doppler ultrasound techniques into the Intensive Care setting has revolutionised the way haemodynamic status is monitored in the critically ill. However, in order to increase the usefulness of these techniques, the Doppler signal and its spectrum need to be further analysed in ways to facilitate a better clinical response. Extensive processing of the Doppler spectrum on Diagnostic ultrasound machines is limited by the real time performance considerations. It was therefore proposed that the spectral information from these systems be extracted off-line and full set of analytical tools be made available to evaluate this information. This was achieved by creating an integrated and modular software tool called Spectron, which was intended as an aid in the overall management of the patients. The modular nature of Spectron was intended to ensure that new analytical tools and techniques could be easily added and tested. The software provides its users with considerable latitude in choosing various data acquisition and analysis parameters to suit various clinical situations and patient requirements. Spectron was developed under the Windows environment to provide a user friendly interface and to address a range of programming problems such as memory management and the size of the colour palettes. Spectron is able to detect the maximal velocities and compute the mean and median velocities. Relative increases in maximal velocities in cardiac blood flows after the administration of inotropic drugs have been shown in the pilot studies that were conducted. Spectron is able to help in obtaining estimates of the aortic blood flows and in other applications such measuring vascular impedance. Stenotic blood flows can be detected by using the spectral broadening index and blood flow characteristics can be studied by using various blood flow indices. Thus, this project attempted to help in patient management by providing clinicians with a range of blood flow parameters and has succeeded in meeting its objective to a large extent