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Dissertations / Theses on the topic 'Imaging'
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1
Olsson, CJ. "Imaging imagining actions." Doctoral thesis, Umeå : Section for Physiology, Department of Integrative Medical Biology, Umeå University, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-1910.
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Sharkey-Toppen, Travis P. "Imaging Iron and Atherosclerosis by Magnetic Resonance Imaging." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1429796182.
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Laudereau, Jean-Baptiste. "Acousto-optic imaging : challenges of in vivo imaging." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066414/document.
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Les tissus biologiques sont des milieux fortement diffusant pour la lumière. En conséquence, les techniques d'imagerie actuelles ne permettent pas d'obtenir un contraste optique en profondeur à moins d'user d'approches invasives. L'imagerie acousto-optique (AO) est une approche couplant lumière et ultrasons (US) qui utilise les US afin de localiser l'information optique en profondeur avec une résolution millimétrique. Couplée à un échographe commercial, cette technique pourrait apporter une information complémentaire permettant d'augmenter la spécificité des US. Grâce à une détection basée sur l'holographie photoréfractive, une plateforme multi-modale AO/US a pu être développée. Dans ce manuscrit, les premiers tests de faisabilité ex vivo sont détaillés en tant que premier jalon de l'imagerie clinique. Des métastases de mélanomes dans le foie ont par exemple été détectées alors que le contraste acoustique n'était pas significatif. En revanche, ces premiers résultats ont souligné deux obstacles majeurs à la mise en place d'applications cliniques.Le premier concerne la cadence d'imagerie de l'imagerie AO très limitée à cause des séquences US prenant jusqu'à plusieurs dizaines de secondes. Le second concerne le speckle qui se décorrèle en milieu vivant sur des temps inférieurs à 1 ms, trop rapide pour les cristaux photorefractif actuellement en palce. Dans ce manuscrit, je propose une nouvelle séquence US permettant d'augmenter la cadence d'imagerie d'un ordre de grandeur au moins ainsi qu'une détection alternative basée sur le creusement de trous spectraux dans des cristaux dopés avec des terres rares qui permet de s'affranchir de la décorrélation du speckleBiological tissues are very strong light-scattering media. As a consequence, current medical imaging devices do not allow deep optical imaging unless invasive techniques are used. Acousto-optic (AO) imaging is a light-ultrasound coupling technique that takes advantage of the ballistic propagation of ultrasound in biological tissues to access optical contrast with a millimeter resolution. Coupled to commercial ultrasound (US) scanners, it could add useful information to increase US specificity. Thanks to photorefractive crystals, a bimodal AO/US imaging setup based on wave-front adaptive holography was developed and recently showed promising ex vivo results. In this thesis, the very first ones of them are described such as melanoma metastases in liver samples that were detected through AO imaging despite acoustical contrast was not significant. These results highlighted two major difficulties regarding in vivo imaging that have to be addressed before any clinical applications can be thought of.The first one concerns current AO sequences that take several tens of seconds to form an image, far too slow for clinical imaging. The second issue concerns in vivo speckle decorrelation that occurs over less than 1 ms, too fast for photorefractive crystals. In this thesis, I present a new US sequence that allows increasing the framerate of at least one order of magnitude and an alternative light detection scheme based on spectral holeburning in rare-earth doped crystals that allows overcoming speckle decorrelation as first steps toward in vivo imaging
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Yoshimaru, Eriko Suzanne. "Magnetic Resonance Imaging Techniques for Rodent Pulmonary Imaging." Diss., The University of Arizona, 2013. http://hdl.handle.net/10150/293388.
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Magnetic Resonance Imaging (MRI) is a safe and widely used diagnostic imaging method that allows in vivo observation of anatomy and characterization of tissues. MRI provides a method to monitor patients without invasive measures, making it suitable for both diagnostics and longitudinal monitoring of various pathologies. A notable example of this is the work carried out by the Alzheimer's Disease Neuroimaging Initiative (ADNI), which utilizes imaging, including multiple MRI techniques, to monitor disease progression in AD patients and evaluates treatment responses and prevention strategies. Similarly, MRI has been extensively used in evaluating diseases in a variety of animal models. In order to detect subtle anatomical changes over time, small differences in MR images must be accurately extracted. Furthermore, to ensure that the extracted differences are due to anatomical changes rather than equipment variance, it becomes essential to monitor and to assess the MRI system stability. In the first chapter of the dissertation, a method for monitoring pre-clinical MRI system performance is discussed. The technique developed during the study provides a fast and simple method to monitor pre-clinical MRI systems but also has applications for all areas of MRI. The second chapter describes the development of a 3D UTE MRI method for pulmonary imaging in freely breathing mice. The development of the 3D UTE sequence for pulmonary MRI has demonstrated its ability to collect images without noticeable motion artifacts and with appreciable signal from the lung parenchyma. Furthermore, images at two distinct respiratory phases were reconstructed from a single data set, providing functional information of the rodents' lungs. Finally, in the third chapter, 3D ¹⁹F UTE MRI is evaluated for imaging in vivo distributions of perfluorocarbon (PFC) nanoemulsions for measuring pulmonary inflammation. Building upon the development of pulmonary imaging, fluorinated contrast agents made from PFCs were used to target immune cells in response to pulmonary pathology. Both 3D ¹H and ¹⁹F UTE MRI were used to acquire pulmonary images of mouse models documented to have pulmonary pathology. Even though the mice had confirmed elevation in alveolar macrophage counts, no visible ¹⁹F signal accumulation within the pulmonary tissue was observed with MRI.
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Pietrzak, John D. "Imaging sonoluminescence." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1993. http://handle.dtic.mil/100.2/ADA277302.
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Thesis (M.S. in Physics) Naval Postgraduate School, December 1993.Thesis advisor(s): Xavier K. Maruyama ; Anthony A. Atchley. "December 1993." Includes bibliographical references. Also available online.
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Geday, Morten A. "Birefringence imaging." Thesis, University of Oxford, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365446.
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Mann, Steve 1962. "Personal imaging." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/45496.
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Thesis (Ph.D.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts & Sciences, 1997.Includes bibliographical references (p. 217-223).
by Steve Mann.
Ph.D.
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Ashpole, Nicole, Mitra Adeli, Nicholas Bostwick, Benn Gleason, Samuel Goldstein, and Taylor Sorenson. "Endoscopic Imaging." Thesis, The University of Arizona, 2010. http://hdl.handle.net/10150/146200.
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For our senior design project, the goal was to design, build and fully characterize an endoscope to be used for cancer research. Currently, medications to be FDA approved for cancer treatment, are tested on mice, in which the only way to obtain data is to periodically euthanize a portion of the mice and perform autopsies to see their colons. This endoscope will allow cancer researchers to observe the distal colons of these mice by allowing researchers to obtain optical coherent tomography, surface magnifying chromendoscopy and laser-induced fluorescence images.
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Spence, Dan Kenrick. "Array combination for parallel imaging in Magnetic Resonance Imaging." Texas A&M University, 2003. http://hdl.handle.net/1969.1/5944.
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In Magnetic Resonance Imaging, the time required to generate an image is
proportional to the number of steps used to encode the spatial information. In rapid
imaging, an array of coil elements and receivers are used to reduce the number of
encoding steps required to generate an image. This is done using knowledge of the
spatial sensitivity of the array and receiver channels. Recently, these arrays have begun
to include a large number of coil elements. Ideally, each coil element would have its
own receiver channel to acquire the image data. In practice, this is not always possible
due to economic or other constraints. In this dissertation, methods are explored to
combine a large array to a limited number of receivers so as to optimize the performance
for parallel imaging; this dissertation focuses on SENSE in particular. Simple
combinations that represent larger coils that might be constructed are discussed. More
complex solutions form current sheets. One solution uses Roemer'ÃÂÃÂs method to optimize
image SNR at a set of points. In this dissertation, Roemer's solution is generalized to
give the weighting coefficients that optimize SNR over regions. Also, solutions fitted to
ideal profiles that minimize noise amplification are shown. These fitted profiles can
allow the SENSE algorithm to function at optimal reduction factors. Finally, a
description of how to build the combiner in hardware is discussed.
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Bao, Sumi. "Clinically relevant magnetic resonance imaging and spectroscopic imaging development." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/9133.
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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1999.Includes bibliographical references (p. 129-137).
As one result of this thesis, a single slab 3D fast spin echo imaging (3DFSE) method has been implemented and optimized. This involved sequence design and implementation, SAR considerations, parameter adjustments and clinical testing. The method can deliver 3D Tl or T2 weighted brain image with isotropic Imm3 voxel resolution in approximately 10 minutes. The ability to obtain high spatial resolution in reasonable time periods has wide clinical applications such as improvement of treatment planning protocols for brain tumor patients, precise radiotherapy planning, and tissue segmentation for following the progression of diseases like multiple sclerosis. The other part of this thesis is devoted to developing and implementing spectroscopic imaging methods, which include 20 chemical shift imaging(2DCSI) methods, 20 line scan spectroscopic imaging(2D LSSI) methods, spin echo planar spectroscopic imaging(SEPSI) methods and ~ingle shot line scan spin echo planar spectroscopic imaging(SSLSEPSI) method. The former two methods are applied to oil phantoms and bone marrow studies. The SEPSI method can provide simultaneous spectroscopic measurements, R2 and R2' images and field distribution images. A time domain spectral analysis method, LP-HSVD was implemented and applied to spectroscopic imaging studies. The SEPSI method was applied to get lipid characterization of bone marrow as well as to get the R2 and R2' brain images. The SSLSEPSI method can provide instant line spectroscopic imaging which might be useful to image moving objects and can provide high temporal resolution for dynamic studies. With further development, both SEPSI and SSLSEPSI methods may prove useful for trabecular bone studies as well as functional magnetic resonance imaging( tMRI) studies.
by Sumi Bao.
Ph.D.
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Lee, Peter. "Scalable multi-parametric imaging of excitable tissue : cardiac imaging." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:a2594103-894b-4e1c-bdbb-43886f0d7fe0.
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The field of cardiac electrophysiological imaging has advanced tremendously in the past three decades with developments in fluorescent dyes, photodetectors, optical filters, illumination sources, computers and electronics. This thesis describes several scalable multi-parametric imaging systems and their application to cardiac tissue preparations at various levels of complexity. Using off-the-shelf components, single-camera multi-parametric optical mapping systems are described for various fluorescent dye combinations and single-element photodiode-based fibre-optic detection systems are described for drug-testing applications. The instruments described take advantage of modern voltage-sensitive dyes, multi-band optical filters and powerful light-emitting-diodes, from the ultraviolet to the red. The two electrophysiological parameters focused on were transmembrane voltage and the intracellular calcium concentration. Several voltage and calcium dye combinations were established, which produce no signal cross-talk. Furthermore, second- and third-generation voltage dyes were characterized in cardiac tissue, in vitro and in vivo. The developed systems were then applied to isolated Langendorff-perfused whole-hearts, in vivo whole-hearts, thin ventricular tissue-slices and human induced pluripotent stem cell-derived cardiac tissue. The interventions applied include accurately-timed electrical and mechanical local stimulation of the whole-heart to generate ectopic beats, cardiotoxic drugs and flash-photolysis of caged-compounds. With the high-throughput demands of drug discovery and testing, further development of scalable optical electrophysiological systems may prove critical in reducing attrition and costs. And for in vivo optical mapping, development of minimally-invasive and clinically-relevant optical systems will be essential in validating existing theories based on in vitro experiments and exploring cardiac function and behaviour with the heart intact in the organism.
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Alomari, Zainab Rami Saleh. "Plane wave imaging beamforming techniques for medical ultrasound imaging." Thesis, University of Leeds, 2017. http://etheses.whiterose.ac.uk/18127/.
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In ultrasound array imaging, the beamforming operation is performed by aligning and processing the received echo signals from each individual array element to form a complete image. This operation can be performed in many different ways, where adaptive and non-adaptive beamformers are considered as the main categories. Adaptive beamformers exploit the statistical correlation between the received data to find a weighting value at the focal point, instead of using a fixed weighting window in non-adaptive beamforming. This results in a significant improvement in the image quality in terms of resolution and sidelobes reduction. This improvement is necessary for ultrafast imaging because of the lack of focusing in Plane Wave Imaging (PWI) that results in lowering the SNR, and thus the produced imaging quality is reduced. This thesis analyses different adaptive beamforming techniques for ultrafast imaging. For accurate medical diagnosis, the frame rate, the imaging resolution, contrast and speckle homogeneity are all considered as important parameters that contribute to the final imaging result. To be able to evaluate each technique by minimizing the effect of external parameters, two different analysis were performed. First an empirical expression for PWI lateral resolution is produced after studying the effect of the imaging parameters on this imaging method. Then a method for selecting the suitable steering angles in Compound Plane- Wave Imaging (CPWI) is introduced, with a detailed explanation for the effect of the compound angles on resolution and sidelobes level. In order to add the contrast improvement to the properties of adaptive beamformers, some techniques like the coherence-based factors and Eigenspace-Based Minimum Variance (ESBMV) are produced in the literature. After demonstrating the principle of Minimum Variance adaptive beamformer, a detailed comparison for the types of coherence-based factors is given. In addition, a new technique of Partial-ESBMV is introduced to modify reference ESBMV so that no Black Box Region artefacts nor dark spots appear when using this method in medical imaging. After explaining its background and properties using cystic and wire phantoms, the proposed method is applied to the real RF data of carotid artery, as an application to clarify the efficiency of this method in medical ultrasound imaging.
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Hoy, Paul R. "Imaging of mice and men : adventures in multispectral imaging." Thesis, University of Southampton, 2009. https://eprints.soton.ac.uk/70911/.
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Cancer of the brain and CNS account for only 2% of new cancer cases in the UK however it is responsible for 7% of cancer deaths of those aged under 70 years of age. Although surgery falls short of a cure it is the primary method of treatment. Two of the key problems in tumour surgery in the brain are a) that many tumours are visually indistinguishable from normal tissue even for experienced surgeons and b) that the risk of post-surgical neurological deficit is related to the proximity of functional (or 'eloquent') neurological tissue. In collaboration with surgeons at the Southampton University NHS Hospitals Trust we seek to address both of these problems. Firstly there is literature evidence that normal and neoplastic tissue have different spectral characteristics in the visible and near-infrared region. We investigate whether these can be practically imaged intraoperatively to establish disease state. Secondly the redox state of haemoglobin is known to affect it's visible and near-infrared spectral characteristics. This project investigates whether it is possible to identify the haemodynamic response associated with functional activity intraoperatively in the human brain. Prion diseases are fatal chronic neurodegenerative diseases of animals and man. They have gained notoriety due to recent outbreaks of Bovine Spongiform Encephalopathy (BSE) and the evidence that they can be transmitted between species, including to man. Exposure to BSE infected material has been shown to cause variant Creutzfeldt-Jacob disease in man. Prion disease is also used as a model of other neurodegenerative diseases, such as Alzheimers disease. Remarkably little is known about this class of disease including the specific cause of the neurodegeneration. Prions are a mis-folded protein which have a different conformation than the normal protein. Certain spectral features in the mid infrared region are associated with protein conformation. In collaboration with neuro-biologists within the university and using a synchrotron light source we investigate the application of multispectral imaging in early stage prion disease. By analysis of the protein conformation sensitivity of the mid infrared spectra (with particular interest in the Amide I band) we seek to identify structurally relevant markers in a mouse model before clinical symptoms of the disease are evident. This may lead to better understanding of the disease progression and the neurotoxic element
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Somoza, Eduardo A. Jr. "UTILIZATION OF FLUORESCENCE MOLECULAR IMAGING TO OPTIMIZE RADIONUCLIDE IMAGING." Case Western Reserve University School of Graduate Studies / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=case1338904705.
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Edalati, Ahmadsaraei Masoud. "Diffusion Tensor Imaging: Application to Cardiovascular Magnetic Resonance Imaging." University of Cincinnati / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1470754609.
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Bianchi, Andrea. "Magnetic resonance imaging techniques for pre-clinical lung imaging." Thesis, Bordeaux, 2014. http://www.theses.fr/2014BORD0060/document.
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Dans ce travail, les s´séquences Imagerie par Résonance Magnétique (IRM) radiales à temps d’écho ultra-court (UTE) sont analysées pour évaluer leur potentiel dans l’étude non-invasive de différents modèles expérimentaux de maladies pulmonaires chez la souris. Chez le petit animal, les séquences radiales UTE peuvent efficacement limiter l’impact négatif sur la qualité de l’image dû au déphasage rapide des spins causé par les nombreuses interfaces air/tissu. En plus, les séquences radiales UTE sont moins sensibles aux artefacts de mouvement par rapport aux séquences Cartésiennes classiques. En conséquence, chez le petit animal, les séquences radiales UTE peuvent permettre d’obtenir des images du poumon avec une résolution bien inférieure au millimètre avec des rapports signal/bruit importants dans le parenchyme pulmonaire, tout en travaillant en conditions physiologiques (animaux en respiration spontanée). Dans cette thèse, il sera démontré que les séquences d’IRM protonique UTE sont outils efficaces dans l’étude quantitative et non-invasive de différents marqueurs distinctifs de certaines pathologies pulmonaires d’intérêt général. Les protocoles développés serontsimples, rapides et non-invasifs, faciles à implémenter, avec une interférence minimale sur la pathologie pulmonaire étudiée et, en définitive, potentiellement applicables chez l’homme. Il sera ainsi démontré que l’emploi des agents de contraste, administrés via les voies aériennes, permet d’augmenter la sensibilité des protocoles développés. Parallèlement, dans cette thèse des protocoles suffisamment flexibles seront implémentés afin de permettre l’étude d’un agent de contraste paramagnétique générique pour des applications aux poumonsIn this work, ultra-short echo time (UTE) Magnetic Resonance Imaging (MRI) sequences are investigated as flexible tools for the noninvasive study of experimental models of lung diseases in mice. In small animals radial UTE sequences can indeed efficiently limit the negative impact on lung image quality due to the fast spin dephasing caused by the multiple air/tissue interfaces. In addition, radial UTE sequences are less sensitive to motion artifacts compared to standard Cartesian acquisitions. As a result, radial UTE acquisitions can provide lung images in small animals at sub-millimetric resolution with significant signal to noise ratio in the lung parenchyma, while working with physiological conditions (freely-breathing animals). In this thesis, UTE proton MRI sequences were shown to be efficient instruments to quantitatively investigate a number of hallmarks in longitudinal models of relevant lung diseases with minimal interference with the lung pathophysiology, employing easilyimplementable fast protocols. The synergic use of positive contrast agents, along with anadvantageous administration modality, was shown to be a valuable help in the increase of sensitivity of UTE MRI. At the same time, UTE MRI was shown to be an extremely useful and efficacious sequence for studying positive contrast agents in lungs
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Wallyn, Justine. "Stealth nanoparticles for preclinical X-rays imaging and multimodal X-rays/MRI (magnetic resonance imaging) imaging." Thesis, Strasbourg, 2017. http://www.theses.fr/2017STRAF074.
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L’imagerie biomédicale est aujourd’hui un outil essentiel pour établir un diagnostic grâce à l’observation des tissus et des fluides biologiques. L’usage d’instruments à imagerie combinée avec des produits de contraste est la clé pour réussir à distinguer précisément un tissu ciblé via l’accumulation de produit de contraste dans le tissu. Les deux principaux appareils à imagerie utilisés sont le scanner à rayons X et l’imagerie à résonance magnétique (IRM). Ils sont fréquemment employés en complément de l’un et l’autre. Typiquement, de petites molécules iodées hydrophiles sont utilisées comme produit de contraste pour la radiographie à rayons X tandis que l’IRM implique des matériaux magnétiques tels que des nanoparticules d’oxyde de fer. Dans le cadre de ce projet doctoral, nous avons donc proposé deux nouveaux produits de contraste dont le premier visait à constituer une alternative aux produits iodés dont la rapide élimination et la toxicité rénale forment deux problèmes récurrents et un second produit, cette fois-ci bimodale, afin de faciliter les procédures d’imagerie bimodale. Pour le premier point, des nanoparticules de polymères iodés pour l’imagerie à rayons X ont été formulées et ce, par une technique de nanoprécipitation. Les paramètres de formulation ont été élucidés de telle sorte que les nanoparticules possédaient une distribution de taille adaptée pour l’administration par voie intraveineuse et une teneur en iode suffisante en iode pour contraster sous rayons X. Une étude in vivo a révélé le potentiel du produit de contraste à visualiser distinctement le foie et la rate et ce, tout en ne présentant pas les principaux problèmes des produits iodés commerciaux. La seconde étude a eu pour but de formuler des nano-véhicules lipidiques capables de générer un contraste pour l’imagerie à rayons X et l’IRM de par l’incorporation d’huile iodée et de nanoparticules d’oxyde de fer dans le coeur de nano-émulsions. Ceci avait pour objectif de fournir une plateforme nanoparticulaire bimodale pour réaliser efficacement et rapidement des procédures d’imagerie multimodale. Nous avons réussi à produire un efficace agent de contraste bimodal permettant d’observer distinctement le foie et les reins par IRM et le foie et la rate par imagerie à rayons X. La pharmacocinétique de la substance administrée a ainsi pu être mise en avant grâce à la bimodalité de l’agent. Employer l’IRM a permis de montrer qu’une fraction de la dose injectée était éliminée par voie rénale tandis que l’imagerie à rayons X a confirmé que les deux tissus, foie et rate,étaient passivement ciblés par l’agent de contraste. Ces deux études ont donc fournies de potentielles solutions pour répondre aux besoins en produits pour l’imagerie à rayons X et en formulations facilitant l’imagerie bimodale des tissus mousBiomedical imaging is nowadays an essential tool to establish a diagnosis by means of observation of tissues and biological fluids. Combination of imaging instrument with contrast enhancers is a key to obtain clear delineation of a desired tissue by accumulation of a contrast agent into this specific target. The two main imagers are the X-ray scanner and the magnetic resonance imaging (MRI).These imagers are frequently used in conjuncture. Typically, small hydrosoluble iodinated molecules are used as contrasting material for radiography whereas MRI involves magnetic materials like iron oxide nanoparticles. In this work, we proposed two novel contrast agents, the first one was aiming to form an alternative to iodinated contrast agents suffering from fast excretion and causing renal toxicity whereas the second one was aiming at providing bimodal contrasting ability to facilitate access to bimodal imaging procedure in clinics. In the first case, iodinated polymeric nanoparticles, serving for preclinical X-ray imaging were formulated by nanoprecipitation technique. Parameters of formulation were elucidated to provide nanoparticles with size distribution suitable for in vivo administration and high iodine content for contrast enhancement. In vivo study revealed the efficacy of our nanoparticles to clearly visualize liver and spleen and limiting current issues associated with marketed radiopaque contrast agents. The second work achieved was aiming at formulating bimodal lipids-based nanocarriers capable of yielding contrast enhancement for X-ray imaging and MRI by combining iodinated oil and iron oxide nanoparticles within a nano-emulsion core. This would provide bimodal nanoparticulate platform to carry out fast and efficient dual modal imaging procedures. In this context we succeeded to generate efficient dual modal contrast agent yielding clear visualization of liver and kidney by MRI and liver and spleen by X-ray imaging. Pharmacokinetic profile was so determined thanks to bimodal imaging. Using MRI allowed to show that kidneys eliminated a fraction of the dose whereas X-ray imaging confirmed that both tissues, liver and spleen, were passively targeted. These two studies proposed solutions limiting current issues of radiopaque contrast agents and novel formulations to facilitate bimodal imaging for soft tissues imaging
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Rajanayagam, Vasanthakumar. "Non-medical applications of imaging techniques : multi-dimensional NMR imaging." Thesis, University of British Columbia, 1986. http://hdl.handle.net/2429/27513.
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The work described in this thesis concentrates on two aspects of Proton NMR imaging: development and evaluation of new/old experimental sequences and application of those techniques to study some non-medical systems that are of industrial importance.
Two-dimensional Fourier transform spin warp imaging technique has been evaluated. Importantly, the adaptation of a conventional high resolution spectrometer to perform imaging has been demonstrated with means of "phantoms". This includes calibration of magnetic field gradients, mapping the static magnetic field and radiofrequency field distributions and intensity measurements related to proton spin densities. In addition, a preliminary study describes microscopic imaging of glass capillary tube phantoms containing water.
Several different sequences related to Chemical Shift imaging including the one developed during the study have been described. A brief insight into chemical shift artifacts as well as some experimental methods of minimizing some of them have also been presented.
The potential of NMR imaging to study non-medical systems has been explored in three different areas of interest: Chromatography columns. Porous rock samples and Wood samples. A variety of NMR imaging sequences have been used to study some interesting and challenging features of these systems which clearly extends the scope of NMR imaging science.Science, Faculty of
Chemistry, Department of
Graduate
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Han, Ling, and Ling Han. "Advances in Gamma-Ray Imaging with Intensified Quantum-Imaging Detectors." Diss., The University of Arizona, 2017. http://hdl.handle.net/10150/626672.
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Nuclear medicine, an important branch of modern medical imaging, is an essential tool for both diagnosis and treatment of disease. As the fundamental element of nuclear medicine imaging, the gamma camera is able to detect gamma-ray photons emitted by radiotracers injected into a patient and form an image of the radiotracer distribution, reflecting biological functions of organs or tissues. Recently, an intensified CCD/CMOS-based quantum detector, called iQID, was developed in the Center for Gamma-Ray Imaging. Originally designed as a novel type of gamma camera, iQID demonstrated ultra-high spatial resolution (<100 micron) and many other advantages over traditional gamma cameras. This work focuses on advancing this conceptually-proven gamma-ray imaging technology to make it ready for both preclinical and clinical applications. To start with, a Monte Carlo simulation of the key light-intensification device, i.e. the image intensifier, was developed, which revealed the dominating factor(s) that limit energy resolution performance of the iQID cameras.
For preclinical imaging applications, a previously-developed iQID-based single-photon-emission computed-tomography (SPECT) system, called FastSPECT III, was fully advanced in terms of data acquisition software, system sensitivity and effective FOV by developing and adopting a new photon-counting algorithm, thicker columnar scintillation detectors, and system calibration method. Originally designed for mouse brain imaging, the system is now able to provide full-body mouse imaging with sub-350-micron spatial resolution.
To further advance the iQID technology to include clinical imaging applications, a novel large-area iQID gamma camera, called LA-iQID, was developed from concept to prototype. Sub-mm system resolution in an effective FOV of 188 mm × 188 mm has been achieved. The camera architecture, system components, design and integration, data acquisition, camera calibration, and performance evaluation are presented in this work. Mounted on a castered counter-weighted clinical cart, the camera also features portable and mobile capabilities for easy handling and on-site applications at remote locations where hospital facilities are not available.
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George, Jonathan Keith. "Polar Synthetic Imaging| Single Pixel Imaging with Rotating Spiral Masks." Thesis, The George Washington University, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=1566270.
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The use of spiral masks placed in front of a single pixel and rotated in time is investigated as a method of single pixel imaging. Single pixel imaging allows an image to be reconstructed from samples of a single pixel over time. This sampling has traditionally been accomplished with liquid crystal arrays or digital micromirror devices. A set of rotating spiral masks in the aperture offer an alternative solution that may reduce complexity and cost for some imaging applications.
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Young, Victoria Eleanor Louise. "Enhancement of carotid magnetic resonance imaging with diffusion weighted imaging." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.648278.
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Jagannathan, Preshanth. "Full Mueller imaging: direction dependent corrections in polarimetric radio imaging." Doctoral thesis, University of Cape Town, 2018. http://hdl.handle.net/11427/28421.
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Magnetic fields pervade the universe, spanning a multitude of scales from the dipolar field on Earth, to the largest gravitationally bound structures such as galaxy clusters [1]. The magnetic fields play a vital role in the evolution of these astronomical systems. In addition to the multitude of scales, magnetic fields are present in different astronomical systems of varying strengths. The strongest observed astronomical magnetic fields are in neutron stars with a field strength of ≈ 1015 G [2], far higher than any man-made fields till date. In stark contrast magnetic fields in the interstellar medium while ubiquitous are only a few µG in field strength. Many fundamental processes in astrophysics have magnetism at their heart, be it cosmic ray particle acceleration, star formation, or the launch of radio galaxy jets, pulsars, etc. One key fundamental process that allows us to detect and characterize cosmic magnetic fields with radio astronomy is the polarization of synchrotron radiation. Synchrotron radiation is intrinsically polarized broadband continuum radiation emitted by relativistic charged particles accelerated by the presence of magnetic fields. The emissivity of the synchrotron radiation is tied to the magnetic field strength B and the spectral index α (defined such that the flux density S ∝ ν −α ) such that ε ∝ B 1+α .
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Steyer, Grant. "Imaging of Cardiovascular Cellular Therapeutics with a Cryo-imaging System." Case Western Reserve University School of Graduate Studies / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=case1264865581.
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Steyer, Grant J. "IMAGING OF CARDIOVASCULAR CELLULAR THERAPEUTICS WITH A CRYO-IMAGING SYSTEM." Case Western Reserve University School of Graduate Studies / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=case1271182554.
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Bishop, James Hart. "Imaging Pain And Brain Plasticity: A Longitudinal Structural Imaging Study." ScholarWorks @ UVM, 2017. http://scholarworks.uvm.edu/graddis/786.
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Chronic musculoskeletal pain is a leading cause of disability worldwide yet the mechanisms of chronification and neural responses to effective treatment remain elusive. Non-invasive imaging techniques are useful for investigating brain alterations associated with health and disease. Thus the overall goal of this dissertation was to investigate the white (WM) and grey matter (GM) structural differences in patients with musculoskeletal pain before and after psychotherapeutic intervention: cognitive behavioral therapy (CBT). To aid in the interpretation of clinical findings, we used a novel porcine model of low back pain-like pathophysiology and developed a post-mortem, in situ, neuroimaging approach to facilitate translational investigation.
The first objective of this dissertation (Chapter 2) was to identify structural brain alterations in chronic pain patients compared to healthy controls. To achieve this, we examined GM volume and diffusivity as well as WM metrics of complexity, density, and connectivity. Consistent with the literature, we observed robust differences in GM volume across a number of brain regions in chronic pain patients, however, findings of increased GM volume in several regions are in contrast to previous reports. We also identified WM changes, with pain patients exhibiting reduced WM density in tracts that project to descending pain modulatory regions as well as increased connectivity to default mode network structures, and bidirectional alterations in complexity. These findings may reflect network level dysfunction in patients with chronic pain.
The second aim (Chapter 3) was to investigate reversibility or neuroplasticity of structural alterations in the chronic pain brain following CBT compared to an active control group. Longitudinal evaluation was carried out at baseline, following 11-week intervention, and a four-month follow-up. Similarly, we conducted structural brain assessments including GM morphometry and WM complexity and connectivity. We did not observe GM volumetric or WM connectivity changes, but we did discover differences in WM complexity after therapy and at follow-up visits.
To facilitate mechanistic investigation of pain related brain changes, we used a novel porcine model of low back pain-like pathophysiology (Chapter 6). This model replicates hallmarks of chronic pain, such as soft tissue injury and movement alteration. We also developed a novel protocol to perform translational post-mortem, in situ, neuroimaging in our porcine model to reproduce WM and GM findings observed in humans, followed by a unique perfusion and immersion fixation protocol to enable histological assessment (Chapter 4).
In conclusion, our clinical data suggest robust structural brain alterations in patients with chronic pain as compared to healthy individuals and in response to therapeutic intervention. However, the mechanism of these brain changes remains unknown. Therefore, we propose to use a porcine model of musculoskeletal pain with a novel neuroimaging protocol to promote mechanistic investigation and expand our interpretation of clinical findings.
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Killich, Markus. "Tissue Doppler Imaging." Diss., lmu, 2007. http://nbn-resolving.de/urn:nbn:de:bvb:19-67089.
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Dhillon, Ravinder. "Diagnostic imaging pathways." University of Western Australia. School of Medicine and Pharmacology, 2007. http://theses.library.uwa.edu.au/adt-WU2007.0126.
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[Truncated abstract] Hypothesis: There is deficiency in the evidence base and scientific underpinning of existing diagnostic imaging pathways (DIP) for diagnostic endpoints. Objective: a) To carry out systematic review of literature in relation to use of diagnostic imaging tests for diagnosis and investigation of 78 common clinical problems, b) To identify deficiencies and controversies in existing diagnostic imaging pathways, and to develop a new set of consensus based pathways for diagnostic imaging (DIP) supported by evidence as an education and decision support tool for hospital based doctors and general practitioners, c) To carry out a trial dissemination, implementation and evaluation of DIP. Methods: 78 common clinical presentations were chosen for development of DIP. For general practitioners, clinical topics were selected based on the following criteria: common clinical problem, complex in regards to options available for imaging, subject to inappropriate imaging resulting in unnecessary expenditure and /or radiation exposure, and new options for imaging of which general practitioners may not be aware. For hospital based junior doctors and medical students, additional criteria included: acute presentation when immediate access to expert radiological opinion may be lacking and clinical problem for which there is a need for education. Systematic review of the literature in relation to each of the 78 topics was carried out using Ovid, Pubmed and Cochrane Database of Systematic Reviews. ... The electronic environment and the method of delivery provided a satisfactory medium for dissemination. Getting DIP implemented required vigorous effort. Knowledge of diagnostic imaging and requesting behaviour tended to become more aligned with DIP following a period of intensive marketing. Conclusions: Systematic review of literature and input and feedback from various clinicians and radiologists led to the development of 78 consensus based Diagnostic Imaging Pathways supported by evidence. These pathways are a valuable decision support tool and are a definite step towards incorporating evidence based medicine in patient management. The clinical and academic content of DIP is of practical use to a wide range of clinicians in hospital and general practice settings. It is source of high level knowledge; a reference tool for the latest available and most effective imaging test for a particular clinical problem. In addition, it is an educational tool for medical students, junior doctors, medical imaging technologists, and allied health care personnel.
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Wang, Lulu. "Virtual imaging system." Click here to access this resource online, 2009. http://hdl.handle.net/10292/668.
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The main purpose of this research project was to implement a combination of computer graphics and processing to generate displays that will aid in the visualization of the colour rendering properties of a range of light sources, including the new generation of high-output LEDs (light emitting diodes) that are becoming widely adopted in general lighting service. The CIE (International Commission on Illumination) has developed a colour appearance model CIECAM02 for use in colour imaging and colour management, and this model is utilized in this work. This thesis describes the design and construction of a computer-based model that can be used as a research tool for the simulation and demonstration of the colour rendering properties of various artificial light sources. It is a comprehensive study of the colour models and measurement procedures currently in use in the lighting industry, as recommended by the CIE. This research project focused on the display of a set of surface colour patches as if they were illuminated by a specific light source, and the simultaneous display of two such sets to demonstrate the surface colour differences arising from the use of the two different light sources. A VIS (virtual imaging system) has been developed to display the colour properties of a series of test colour samples under different light sources. This thesis describes the computer models developed for the representation and display of surface colours in general, and colour rendering in particular. The designed system computes and displays the colour of each sample from a knowledge of the light-source spectrum and the spectral reflectance of each surface. It can simultaneously display the colours resulting from illumination by two different sources. In addition, the system computes the colour appearance differences for two sets of colours using the CIECAM02 colour appearance model. Subjective and objective tests were taken to validate the computed results. The VIS has been designed and implemented. It also has been tested by 21 observers and we believe that it will be a powerful research tool for the lighting industry, especially in relation to colour rendering.
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Youle, Ian. "Quantitative tritium imaging." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0015/NQ45641.pdf.
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Loo, Fook Leong. "Polarimetric thermal imaging." Thesis, Monterey, Calif. : Naval Postgraduate School, 2007. http://bosun.nps.edu/uhtbin/hyperion.exe/07Mar%5FLoo.pdf.
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Thesis (M.S. in Electronic Warfare System Engineering)--Naval Postgraduate School, March 2007.Thesis Advisor(s): Alfred W. Cooper. "March 2007." Includes bibliographical references (p. 101-102). Also available in print.
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Kennedy, Stephanie Michelle. "Imaging cell arrays." Thesis, University of Liverpool, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.539580.
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Barrow, Matthew. "Imaging through obscurants." Thesis, King's College London (University of London), 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286015.
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Rogers, Leon John. "Photofragment ion imaging." Thesis, University of Bristol, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266958.
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Assam, Aieat. "Sensor-enhanced imaging." Thesis, University of Birmingham, 2013. http://etheses.bham.ac.uk//id/eprint/4268/.
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Most approaches to spatial image management involve GPS or image processing. In this thesis, a sensor-focused alternative is explored. It requires user and camera tracking, particularly challenging in indoor environments. Possible indoor tracking methods are evaluated and pedestrian dead reckoning is selected. A study is conducted to evaluate sensors and choose a combination for pedestrian and camera tracking. Gyroscope and accelerometer offer comparable step detection performance, with gyroscope and tilt compensated compass providing heading data. Images taken from the same viewpoint are successfully arranged using panorama stitching without any image processing. The results compare favourably to conventional methods. While lacking visual definition of image processing methods, they can complement them if used in tandem. Sensor compositing and pedestrian tracking are implemented in a unified system. Several methods for fusing compass and gyroscope data are compared, but do not produce statistically significant improvement over using just the compass. The system achieves loop closure accuracy of 91% of path length and performs consistently across multiple participants. The final system can be used in GPS-denied locations and presents an image content independent way of managing photographs. It contributes to pedestrian tracking and image composting fields and has potential commercial uses (illustrated by an example Android app).
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Venkatraman, Dheera. "Quantum-mimetic imaging." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/97762.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2015.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 139-146).
Many recent experiments have explored the use of nonclassical states of light to perform imaging or sensing. Although these experiments require quantum descriptions of light to explain their behavior, the advantages they claim are not necessarily unique to quantum light. This thesis explores the underlying principles behind two of those imaging techniques and realizes classical experiments that demonstrate properties similar to their quantum counterparts. The principal contributions of this thesis in the preceding quantum-mimetic imaging paradigm are the experimental implementation of phase-conjugate optical coherence tomography and phase-sensitive ghost imaging, two experiments whose quantum counterparts utilize phase-sensitive light with nonclassical strength. This thesis also explores the use of compressed sensing to further speed up acquisition of ghost imaging. Finally, a new paradigm inspired by compressed sensing is demonstrated, in which high-quality depth and reflectivity images are simultaneously captured using only the first photon arrival at each pixel. This paradigm is also extended to the case of single-photon APD arrays which may offer few-photon low-light imaging capabilities beyond what is possible with current camera technologies.
by Dheera Venkatraman.
Ph. D.
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Kirmani, Ahmed (Ghulam Ahmed). "Femtosecond Transient Imaging." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/58402.
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Thesis (S.M.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 59-64).
This thesis proposes a novel framework called transient imaging for image formation and scene understanding through impulse illumination and time images. Using time-of-flight cameras and multi-path analysis of global light transport, we pioneer new algorithms and systems for scene understanding through time images. We demonstrate that our proposed transient imaging framework provides opportunities to accomplish tasks that are well beyond the reach of existing imaging technology. For example, one can infer the geometry of not only the visible but also the hidden parts of a scene, enabling us to look around corners. Traditional cameras estimate intensity per pixel I(x, y). Our transient imaging camera prototype captures a 3D time-image I(x, y, t) for each pixel and uses an ultra-short pulse laser for flash illumination. Emerging technologies are supporting cameras with a temporal-profile per pixel at picosecond resolution, allowing us to capture an ultra-high speed time-image. This time-image contains the time profile of irradiance at a sensor pixel. The speed of light is relevant at these imaging time scales, and the transient properties of light transport come into play. In particular we furnish a novel framework for reconstructing scene geometry of hidden planar scenes. We experimentally corroborated our theory with free space hardware experiments using a femtosecond laser and a picosecond accurate sensing device. The ability to infer the structure of hidden scene elements, unobservable by both the camera and illumination source, will create a range of new computer vision opportunities.
by Ahmed Kirmani.
S.M.
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Satat, Guy. "Imaging through scattering." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/98620.
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Thesis: S.M., Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 75-84).
In this thesis we demonstrate novel methods to overcome optical scattering in order to resolve information about hidden scenes, in particular for biomedical applications. Imaging through scattering media has long been a challenge, as scattering corrupts scenes in a non-invertible way. The use of near-visible optical spectrum for biomedical purposes has many advantages, such as optical contrast, optical resolution and nonionizing radiation. Particularly, it has important applications in biomedical imaging, such as sub-dermal imaging for diagnostics, screening and monitoring conditions. We demonstrate methods to overcome and use scattering in order to recover scene parameters. In particular we demonstrate a method for locating and classifying fluorescent markers hidden behind turbid layers using ultrafast time-resolved measurements with a sparse-based optimization framework. This novel method has applications in remote sensing and in-vivo fluorescence lifetime imaging. Another method is demonstrated to resolve blood flow speed within skin tissue. This method is based on a computational photography technique and coherent illumination. This method can be applied in diagnosis and monitoring of burns, wounds, prostheses and cosmetics. A particularly important application of this technology is analysis of diabetic ulcers, which is the main cause for non-traumatic amputations in India. The suggested prototype is suitable for assisting clinicians in assessing the wound healing process. The methods developed in this thesis using ultrafast time-resolved measurements, sparsity-based optimization and computational photography can spur research and applications in biomedical imaging, skin conditions diagnosis and more general modalities of imaging through scattering media.
by Guy Satat.
S.M.
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Liu, Arthur K. (Arthur Kuang-Chung). "Spatiotemporal brain imaging." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/8963.
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Thesis (Ph.D.)--Harvard--Massachusetts Institute of Technology Division of Health Sciences and Technology, 2000.Includes bibliographical references.
Understanding how the human brain works, in both health and disease, requires data with both high spatial and temporal resolution. This thesis develops and applies a spatiotemporal neuroimaging method. I describe a linear estimation inverse approach, which is a method for the combination of functional magnetic resonance imaging (fMRI) with electroencephalography (EEG) and magnetoencephalography (MEG). fMRI provides millimeter spatial resolution, while EEG and MEG provide millisecond temporal resolution. The thesis is divided into two broad sections: Monte Carlo modeling studies and experimental studies. Improvements to both the bioelectromagnetic forward and inverse solutions are demonstrated. Through modeling studies, I characterize the accuracy of the method with and without functional and anatomic constraints, the effects of various model mis-specifications, and as a function of EEG/MEG sensor configuration. I describe a noise sensitivity normalization to the traditional linear estimation operator that improves the point spread function (a measure of spatial resolution), increases the spatial homogeneity of the point spread, and allows interpretation of the localization in terms of a statistical measure (F-statistic). Using experimentally generated current dipoles implanted an epilepsy patient, I examine the accuracy of both a realistic and spherical EEG head model. This experimental data demonstrates the improved accuracy of the realistic head model, and gives us confidence in using this realistic head model for EEG source localization. The optimized and validated forward and inverse methods are then applied to a variety of empirical measurements. First, the combined multi modality imaging approach is used to simultaneous EEG/fMRI measurements of a visual stimulus, demonstrating the feasibility of measuring and localizing simultaneously acquired electric potential and hemodynamic measurements. Second, combined MEG/fMRI measurements are used to analyze the spatiotemporal characteristics of a cortical network that is responsive to visual motion coherency. Finally, in epilepsy patients, I compare the non-invasive MEG localization of interictal spikes with verification from invasive recordings and surgical results. These studies, in both normal volunteers and patients, clearly demonstrate the utility, accuracy, and power of the combined use of fMRI, EEG and MEG. The tools demonstrated here provide "real time movies" of the human brain at work during a given task or behavior. This information is required to develop computational models of how the human brain/mind works.
by ARthur K. Lui.
Ph.D.
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Smith, Joshua Reynolds. "Electric field imaging." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/29144.
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Thesis (Ph.D.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts & Sciences, 1999.Includes bibliographical references (p. 213-216).
The physical user interface is an increasingly significant factor limiting the effectiveness of our interactions with and through technology. This thesis introduces Electric Field Imaging, a new physical channel and inference framework for machine perception of human action. Though electric field sensing is an important sensory modality for several species of fish, it has not been seriously explored as a channel for machine perception. Technological applications of field sensing, from the Theremin to the capacitive elevator button, have been limited to simple proximity detection tasks. This thesis presents a solution to the inverse problem of inferring geometrical information about the configuration and motion of the human body from electric field measurements. It also presents simple, inexpensive hardware and signal processing techniques for making the field measurements, and several new applications of electric field sensing. The signal processing contribution includes synchronous undersampling, a narrowband, phase sensitive detection technique that is well matched to the capabilities of contemporary microcontrollers. In hardware, the primary contributions are the School of Fish, a scalable network of microcontroller-based transceive electrodes, and the LazyFish, a small footprint integrated sensing board. Connecting n School of Fish electrodes results in an array capable of making heterodyne measurements of any or all n(n - 1) off-diagonal entries in the capacitance matrix. The LazyFish uses synchronous undersampling to provide up to 8 high signal-to-noise homodyne measurements in a very small package. The inverse electrostatics portion of the thesis presents a fast, general method for extracting geometrical information about the configuration and motion of the human body from field measurements. The method is based on the Sphere Expansion, a novel fast method for generating approximate solutions to the Laplace equation. Finally, the thesis describes a variety of applications of electric field sensing, many enabled by the small footprint of the LazyFish. To demonstrate the School of Fish hardware and the Sphere Expansion inversion method, the thesis presents 3 dimensional position and orientation tracking of two hands.
by Joshua Reynolds Smith.
Ph.D.
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Wang, L. "Avalanche imaging radar." Thesis, University College London (University of London), 2012. http://discovery.ucl.ac.uk/1344105/.
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Over the past century, due to the significant increase in recreational activities, transportation, construction in high altitude areas, mountain areas all around the world, have been seen substantial development. In these high altitude areas around mountain ranges, avalanche always brings huge threaten to human’s activities and lives. The rising demand for higher safety measures has given new pressure to the development of mitigation technology to protect human in certain areas, and driven rise to a new scientific area entirely devoted to avalanche. A RADAR system can provide superior penetration capability through any type of weather condition, and can be used in the day or night time. A RADAR system uses electromagnetic wave that does not require a medium like Sonar that is using water as medium. Radar also can be long range, because the electromagnetic wave is able to propagate at the speed of light. It is less susceptible to weather conditions compared with Lasers. It does not require target cooperation to emit any signals. The original contribution of this thesis contains four parts: the novel work of snow particles models (option models and HFT model); the simulation of a receiver module in an avalanche radar system; the development of an active baseband filter; and the development of an FPGA chirp generator. The option model and HFT model are built to give solutions and to map and predict the moving route of snow particles. The purposes of proposing these two models are different and the assumptions of both totally diverge. The option model is built on the assumption of knowing all the information about the stop location and start location of an airborne avalanche. The key concept of the option model is the introduction of a binary tree. By using the theories of a binary tree, normal distribution and the knowledge of the stop location and start location of an airborne avalanche, its route can be mapped and the behaviour can be further studied. On the other hand, an HFT model is based on the theories of stochastic process. It does not require any knowledge of the avalanches and can be used to predict the movement of an airborne avalanche. The FPGA chirp generator is built for more flexibility than the DDS waveform generator. The simulation is done in this thesis to help design the receiver module in avalanche radar. And the prototype of the FPGA chirp generator is based on Xilinx virtex-5 development board and avanet high-speed DAC. This new design is different from existing FPGA chirp generator, since it uses the onboard memory to store the chirp signal data, which gives the ability to store more data to significantly increase the sampling rate and resolution of chirp signal.
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Van, der Walt Stefan Johann. "Super-resolution imaging." Thesis, Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/5189.
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Thesis (PhD (Electronic Engineering))--University of Stellenbosch, 2010.Contains bibliography and index.
ENGLISH ABSTRACT: Super-resolution imaging is the process whereby several low-resolution photographs of an object are combined to form a single high-resolution estimation. We investigate each component of this process: image acquisition, registration and reconstruction. A new feature detector, based on the discrete pulse transform, is developed. We show how to implement and store the transform efficiently, and how to match the features using a statistical comparison that improves upon correlation under mild geometric transformation. To simplify reconstruction, the imaging model is linearised, whereafter a polygon-based interpolation operator is introduced to model the underlying camera sensor. Finally, a large, sparse, over-determined system of linear equations is solved, using regularisation. The software developed to perform these computations is made available under an open source license, and may be used to verify the results.
AFRIKAANSE OPSOMMING: In super-resolusie beeldvorming word verskeie lae-resolusie foto's van 'n onderwerp gekombineer in 'n enkele, hoë-resolusie afskatting. Ons ondersoek elke stap van hierdie proses: beeldvorming, -belyning en hoë-resolusie samestelling. 'n Nuwe metode wat staatmaak op die diskrete pulstransform word ontwikkel om belangrike beeldkenmerke te vind. Ons wys hoe om die transform e ektief te bereken en hoe om resultate kompak te stoor. Die kenmerke word vergelyk deur middel van 'n statistiese model wat bestand is teen klein lineêre beeldvervormings. Met die oog op 'n vereenvoudigde samestellingsberekening word die beeldvormingsmodel gelineariseer. In die nuwe model word die kamerasensor gemodelleer met behulp van veelhoek-interpolasie. Uiteindelik word 'n groot, yl, oorbepaalde stelsel lineêre vergelykings opgelos met behulp van regularisering. Die sagteware wat vir hierdie berekeninge ontwikkel is, is beskikbaar onderhewig aan 'n oopbron-lisensie en kan gebruik word om die gegewe resultate te veri eer.
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Wilkinson, James Daniel. "Imaging membrane potential." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:9496dc0b-212c-4355-830c-dbbcb5d7e581.
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Imaging membrane potential is a promising technique in the elucidation of the interactions of large networks of neurons. The membrane potential in a neuron varies as an action potential, the basic electrical signal of neuronal communication, travels along the length of the cell. Voltage sensitive dyes play a key role by providing an optical readout of the electric field generated across a neuron membrane by the action potential. However, none of the dyes reviewed in Chapter 1 generate sufficient signal change with changes in membrane potential; this sensitivity problem limits the ability of the imaging membrane potential technique to allow the high spatial and temporal resolution necessary for neuronal networks to be better understood. This thesis features two avenues of research that are expected to result in the necessary enhancements to voltage sensitive dyes to improve the signal change. The first avenue is based on the effect of an electric field upon the non-linear optical properties of a porphyrin macromolecule. The encouraging field sensitivity of a previous porphyrin monomer voltage sensor inspired an investigation which identified optimisations to enhance the voltage sensitivity (Chapter 2). The design, synthesis and initial characterisation of optimised porphyrin voltage sensors is detailed in Chapter 3. The second avenue is based on the effect of an electric field upon the rate of intermolecular electron transfer. In a suitably designed dye, the competition between electron transfer and fluorescence, following excitation by incoming light, allows the fluorescence intensity to act as an optical indicator of the electron transfer rate. New dyes were rationally designed and synthesised, as this effect had not been applied to voltage sensitive imaging before the research detailed in Chapter 4. The challenging purification of the new amphiphilic dyes synthesised also inspired research into a novel testing method which does not require amphiphilic dyes (Chapter 5).
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Martinello, Manuel. "Coded aperture imaging." Thesis, Heriot-Watt University, 2012. http://hdl.handle.net/10399/2570.
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This thesis studies the coded aperture camera, a device consisting of a conventional camera with a modified aperture mask, that enables the recovery of both depth map and all-in-focus image from a single 2D input image. Key contributions of this work are the modeling of the statistics of natural images and the design of efficient blur identification methods in a Bayesian framework. Two cases are distinguished: 1) when the aperture can be decomposed in a small set of identical holes, and 2) when the aperture has a more general configuration. In the first case, the formulation of the problem incorporates priors about the statistical variation of the texture to avoid ambiguities in the solution. This allows to bypass the recovery of the sharp image and concentrate only on estimating depth. In the second case, the depth reconstruction is addressed via convolutions with a bank of linear filters. Key advantages over competing methods are the higher numerical stability and the ability to deal with large blur. The all-in-focus image can then be recovered by using a deconvolution step with the estimated depth map. Furthermore, for the purpose of depth estimation alone, the proposed algorithm does not require information about the mask in use. The comparison with existing algorithms in the literature shows that the proposed methods achieve state-of-the-art performance. This solution is also extended for the first time to images affected by both defocus and motion blur and, finally, to video sequences with moving and deformable objects.
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Tibbs, Alex. "Bioinspired imaging polarimetry." Thesis, University of Bristol, 2018. http://hdl.handle.net/1983/08eb9263-c101-41e6-b363-ecd652cb192e.
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Many animals perceive changes in the polarization of light in addition to, or instead of, changes in intensity and wavelength, allowing them to more effectively perform tasks. Although humans lack this ability, recent work allows humans to exploit polarization using imaging polarimeters, and many applications which use this technology have been developed. A major challenge of polarimetry is image degradation due to noise, which has led to incorrect conclusions in the literature and reduces the effectiveness of computer vision algorithms. Local feature extraction is a technique for extracting information from images which is a common intermediate step in many computer vision applications. No work has yet been done assessing the performance of existing local feature extraction algorithms with polarimetry, or how they can be most effectively used. In this thesis degradation caused by noise in polarimetry is investigated, and mitigating steps are proposed. Denoising algorithms are then investigated which are shown to improve the peak signal-to-noise ratio of polarization images by 4.5dB over existing algorithms. This is done by adapting an existing denoising algorithm, Block-Matching 3D, to create a method specifically for polarimetry, Polarization-BM3D (PBM3D). PBM3D will be shown to provide superior visual quality to existing algorithms. This thesis also investigates the use of common local feature extraction algorithms with polarimetry, and compares their effectiveness with colour imagery. It will be demonstrated that using local features with polarimetry can yield better results than using colour imagery (by 7.5%), specifically when the Stokes representation is used. It will also be shown that Hessian-affine is the most effective detection algorithm and SIFT is the most effective description algorithm for use with polarimetry. Finally the effects of noise on features extraction with polarimetry will be presented, and it will be shown that PBM3D improves detector and descriptor performance by 35% and 5% respectively.
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Qin, Ruogu. "Intraoperative Imaging Platform." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1322617803.
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Jia, Jie. "Fourier Multispectral Imaging." University of Dayton / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1494159492377494.
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Aspden, Reuben S. "Heralded quantum imaging." Thesis, University of Glasgow, 2015. http://theses.gla.ac.uk/6472/.
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Imaging systems play a crucial role in shaping understanding of our surroundings. Modern imaging systems enable the acquisition of images of objects at length-scales and resolutions previously deemed impossible. However, as the drive for better images and novel applications increases, several questions fundamental to our understanding of imaging are being raised. We are familiar with images containing many millions of photons, but how many photons does it take to form an image? In scenarios requiring covert imaging, or where high-light levels damage the sample being imaged, is it possible to image a sample with a very small number of very low-energy photons? This thesis will focus on answering these two questions. In order to answer these questions I developed a heralded quantum imaging system. The strong spatial correlations inherent between down-converted twin photons have been utilised in many quantum imaging techniques for the past 25 years. Thus far, standard quantum imaging techniques have relied on scanning a fibre detector across the field of view in order to measure the spatial information in the image. However, the scanning mechanism fundamentally limits the detection efficiency of the imaging system. Recent years have seen an increased interest in using the latest camera technology within quantum imaging systems. The advent of single-photon-sensitive cameras has opened up new possibilities within the quantum imaging field. It is now possible to obtain images of objects by detecting very low-light illumination across the full scene simultaneously. In the heralded quantum imaging system presented in this thesis, a combination of quantum mechanics and a high-sensitivity camera was employed to obtain high contrast images containing very few photons. This was the first such system built. Using the correlations between the twin photons generated by our down-conversion source, and our development of compressive sampling techniques to post-process the acquired data enabled the acquisition of an image containing an average of only 0.5 photons per pixel. This represents a significant reduction when compared with a conventional image that contains of order 105 photons per pixel. I also developed this imaging system to use twin photons at vastly different wave- lengths. The object was probed with low-energy infrared photons whilst the image was developed on a camera using the correlated visible photon. This disparity in energy between the two photons enabled the acquisition of images using only several thousand photons, corresponding to an energy deposition on the sample of only a few pJ.
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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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Bradley, Christine Lavella, and Christine Lavella Bradley. "SpectroPolarimetric Imaging Observations." Diss., The University of Arizona, 2017. http://hdl.handle.net/10150/624499.
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The capability to map anthropogenic aerosol quantities and properties over land can provide significant insights for climate and environmental studies on global and regional scales. One of the primary challenges in aerosol information monitoring is separating two signals measured by downward-viewing airborne or spaceborne instruments: the light scattered from the aerosols and light reflected from the Earth's surface. In order to study the aerosols independently, the surface signal needs to be subtracted out from the measurements. Some observational modalities, such as multispectral and multiangle, do not provide enough information to uniquely define the Earth's directional reflectance properties for this task due to the high magnitude and inhomogeneity of albedo for land surface types. Polarization, however, can provide additional information to define surface reflection. To improve upon current measurement capabilities of aerosols over urban areas, Jet Propulsion Laboratory developed the Multiangle SpectroPolarimetric Imager (MSPI) that can accurately measure the Degree of Linear Polarization to 0.5%. In particular, data acquired by the ground-based prototype, GroundMSPI, is used for directional reflectance studies of outdoor surfaces in this dissertation. This work expands upon an existing model, the microfacet model, to characterize the polarized bidirectional reflectance distribution function (pBRDF) of surfaces and validate an assumption, the Spectral Invariance Hypothesis, on the surface pBRDF that is used in aerosol retrieval algorithms.
The microfacet model is commonly used to represent the pBRDF of Earth's surface types, such as ocean and land. It represents a roughened surface comprised of randomly oriented facets that specularly reflect incoming light into the upward hemisphere. The analytic form of the pBRDF for this model assumes only a single reflection of light from the microfaceted surface. If the incoming illumination is unpolarized, as it is with natural light from the Sun, the reflected light is linearly polarized perpendicular to the plane that contains the illumination and view directions, the scattering plane. However, previous work has shown that manmade objects, such as asphalt and brick, show a polarization signature that differs from the single reflection microfacet model. Using the polarization ray-tracing (PRT) program POLARIS-M, a numerical calculation for the pBRDF is made for a roughened surface to account for multiple reflections that light can experience between microfacets. Results from this numerical PRT method shows rays that experience two or more reflections with the microfacet surface can be polarized at an orientation that differs from the analytical single reflection microfacet model. This PRT method is compared against GroundMSPI data of manmade surfaces.
An assumption made regarding the pBRDF for this microfacet model is verified with GroundMSPI data of urban areas. This is known as the Spectral Invariance Hypothesis and asserts that the magnitude and shape of the polarized bidirectional reflectance factor (pBRF) is the same for all wavelengths. This simplifies the microfacet model by assuming some surface parameters such as the index of refraction are spectrally neutral. GroundMSPI acquires the pBRF for five prominent region types, asphalt, brick, cement, dirt, and grass, for day-long measurements on clear sky conditions. Over the course of each day, changing solar position in the sky provides a large range of scattering angles for this study. The pBRF is measured for the three polarimetric wavelengths of GroundMSPI, 470, 660, and 865nm, and the best fit slope of the spectral correlation is reported. This investigation shows agreement to the Spectral Invariance Hypothesis within 10% for all region types excluding grass. Grass measurements show a large mean deviation of 31.1%. This motivated an angle of linear polarization (AoLP) analysis of cotton crops to isolate single reflection cases, or specular reflections, from multiple scattering cases of light in vegetation. Results from this AoLP method show that specular reflections off the top surface of leaves follow the Spectral Invariance Hypothesis.
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Dhillon, Ravinder. "Diagnostic imaging pathways /." Connect to this title, 2006. http://theses.library.uwa.edu.au/adt-WU2007.0126.
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