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Dissertations / Theses on the topic 'Imaging in a neural tissue'
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Hui, Sai-kam, and 許世鑫. "Magnetic resonance diffusion tensor imaging for neural tissue characterization." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B42841306.
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Hui, Sai-kam. "Magnetic resonance diffusion tensor imaging for neural tissue characterization." Click to view the E-thesis via HKUTO, 2009. http://sunzi.lib.hku.hk/hkuto/record/B42841306.
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Eppelheimer, Maggie S. "Identification of Chiari Malformation Type I Brain Morphology and Biomechanics: A Multi-Faceted Approach to Determine Diagnostic and Treatment Criteria." University of Akron / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=akron1595680107882868.
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Mayerich, David Matthew. "Acquisition and reconstruction of brain tissue using knife-edge scanning microscopy." Texas A&M University, 2003. http://hdl.handle.net/1969.1/563.
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A fast method for gathering large-scale data sets through the serial sectioning of
brain tissue is described. These data sets are retrieved using knife-edge scanning
microscopy, a new technique developed in the Brain Networks Laboratory at Texas
A&M University. This technique allows the imaging of tissue as it is cut by an
ultramicrotome.
In this thesis the development of a knife-edge scanner is discussed as well as the
scanning techniques used to retrieve high-resolution data sets. Problems in knife-edge
scanning microscopy, such as illumination, knife chatter, and focusing are discussed.
Techniques are also shown to reduce these problems so that serial sections of tissue can
be sampled at resolutions that are high enough to allow reconstruction of neurons at the
cellular level.
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Abdeladim, Lamiae. "Large volume multicolor nonlinear microscopy of neural tissues." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLX070/document.
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La microscopie non linéaire a transformé le domaine de la neurobiologie depuis les années 1990, en permettant d'acquérir des images tridimensionnelles de tissus épais avec une résolution subcellulaire. Cependant, les profondeurs d'imagerie accessibles sont limitées à quelques centaines de micromètres dans des tissus diffusants tels que le tissu cérébral. Au cours des dernières années, plusieurs stratégies ont été développées pour dépasser cette limitation de profondeur et accéder à de plus grands volumes de tissu. Ces avancées récentes ont jusqu'à présent été limitées en terme de modes de contrastes accessibles, et ont souvent été réduites à des approches monochromes. Ce travail de thèse vise à développer des techniques d'imagerie non linéaires de grands volumes et de grande profondeur dotées de diverses possibilités de contrastes, indispensables pour l'étude de tissus complexes tels que le tissu cérébral. Dans un premier chapitre, nous présentons les difficultés associées à l'imagerie de grand volume de tissu cérébral, avec une emphase particulière sur les puissantes stratégies de marquages génétiques dont l'usage à jusqu'à présent été limité à des faibles étendues. Ensuite, nous introduisons la microscopie Chrom-SMP (chromatic serial multiphoton), une méthode développée au cours de cette thèse et consistant à combiner l’excitation deux-photon multicouleurs par mélange de fréquences avec une technique d'histologie automatisée (i.e découpe sériée) pour accéder à plusieurs contrastes non linéaires à travers de grands volumes de tissus ex vivo, allant de plusieurs mm3 à des cerveaux entiers, avec une résolution micrométrique et un coalignement intrinsèque des canaux spectraux. Dans un troisième chapitre, nous explorons le potentiel de cette nouvelle approche pour la neurobiologie. En particulier, nous démontrons l'histologie multicouleur de plusieurs mm3 de tissu "Brainbow" avec une résolution constante dans l’ensemble du volume imagé. Nous illustrons le potentiel de notre approche à travers l'analyse de la morphologie, des interactions et du lignage des astrocytes du cortex cérébral de souris. Nous explorons également l’apport du Chrom-SMP pour le suivi multiplexé de projections neuronales marquées par des traceurs de couleurs distinctes sur de grandes distances. Enfin, nous présentons dans un quatrième chapitre le développement de la microscopie à trois photons multimodale, approche permettant d’augmenter la profondeur d’imagerie sur tissus vivantsMultiphoton microscopy has transformed neurobiology since the 1990s by enabling 3D imaging of thick tissues at subcellular resolution. However the depths provided by multiphoton microscopy are limited to a few hundreds of micrometers inside scattering tissues such as the brain. In the recent years, several strategies have emerged to overcome this depth limitation and to access larger volumes of tissue. Although these novel approaches are transforming brain imaging, they currently lack efficient multicolor and multicontrast modalities. This work aims at developing large-scale and deep-tissue multiphoton imaging modalities with augmented contrast capabilities. In a first chapter, we present the challenges of high-content large-volume brain imaging, with a particular emphasis on powerful multicolor labeling strategies which have so far been restricted to limited scales. We then introduce chromatic serial multiphoton (Chrom-SMP) microscopy, a method which combines automated histology with multicolor two-photon excitation through wavelength-mixing to access multiple nonlinear contrasts across large volumes, from several mm3 to whole brains, with submicron resolution and intrinsic channel registration. In a third chapter, we explore the potential of this novel approach to open novel experimental paradigms in neurobiological studies. In particular, we demonstrate multicolor volumetric histology of several mm3 of Brainbow-labeled tissues with preserved diffraction-limited resolution and illustrate the strengths of this method through color-based tridimensional analysis of astrocyte morphology, interactions and lineage in the mouse cerebral cortex. We further illustrate the potential of the method through multiplexed whole-brain mapping of axonal projections labeled with distinct tracers. Finally, we develop multimodal three-photon microscopy as a method to access larger depths in live settings
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Channappa, Lakshmi [Verfasser], and Thomas [Akademischer Betreuer] Euler. "Electrical Imaging of Aberrant Activity in Neural Tissues Using High Density Microelectrode Arrays / Lakshmi Channappa ; Betreuer: Thomas Euler." Tübingen : Universitätsbibliothek Tübingen, 2016. http://d-nb.info/1199615544/34.
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Rambani, Komal. "Thick brain slice cultures and a custom-fabricated multiphoton imaging system: progress towards development of a 3D hybrot model." Thesis, Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/22702.
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Development of a three dimensional (3D) HYBROT model with targeted in vivo like intact cellular circuitry in thick brain slices for multi-site stimulation and recording will provide a useful in vitro model to study neuronal dynamics at network level. In order to make this in vitro model feasible, we need to develop several associated technologies. These technologies include development of a thick organotypic brain slice culturing method, a three dimensional (3D) micro-fluidic multielectrode Neural Interface system (µNIS) and the associated electronic interfaces for stimulation and recording of/from tissue, development of targeted stimulation patterns for closed-loop interaction with a robotic body, and a deep-tissue non-invasive imaging system. To make progress towards this goal, I undertook two projects: (i) to develop a method to culture thick organotypic brain slices, and (ii) construct a multiphoton imaging system that allows long-term and deep-tissue imaging of two dimensional and three dimensional cultures.
Organotypic brain slices preserve cytoarchitecture of the brain. Therefore, they make more a realistic reduced model for various network level investigations. However, current culturing methods are not successful for culturing thick brain slices due to limited supply of nutrients and oxygen to inner layers of the culture. We developed a forced-convection based perfusion method to culture viable 700µm thick brain slices.
Multiphoton microscopy is ideal for imaging living 2D or 3D cultures at submicron resolution. We successfully fabricated a custom-designed high efficiency multiphoton microscope that has the desired flexibility to perform experiments using multiple technologies simultaneously. This microscope was used successfully for 3D and time-lapse imaging.
Together these projects have contributed towards the progress of development of a 3D HYBROT.
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3D Hybrot: A hybrid system of a brain slice culture embodied with a robotic body.
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Wellen, Jeremy W. "Characterization of soft-tissue response to mechanical loading using nuclear magnetic resonance (NMR) and functional magnetic resonance imaging (fMRI) of neuronal activity during sustained cognitive-stimulus paradigms." Link to electronic thesis, 2003. http://www.wpi.edu/Pubs/ETD/Available/etd-0430103-140128.
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Bernal, Moyano Jose. "Deep learning for atrophy quantification in brain magnetic resonance imaging." Doctoral thesis, Universitat de Girona, 2020. http://hdl.handle.net/10803/671699.
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The quantification of cerebral atrophy is fundamental in neuroinformatics since it permits diagnosing brain diseases, assessing their progression, and determining the effectiveness of novel treatments to counteract them. However, this is still an open and challenging problem since the performance
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of traditional methods depends on imaging protocols and quality, data harmonisation errors, and brain abnormalities. In this doctoral thesis, we question whether deep learning methods can be used for better estimating cerebral atrophy from magnetic resonance images. Our work shows that deep learning can lead to a state-of-the-art performance in cross-sectional assessments and compete and surpass traditional longitudinal atrophy quantification methods. We believe that the proposed cross-sectional and longitudinal methods can be beneficial for the research and clinical communityLa cuantificación de la atrofia cerebral es fundamental en la neuroinformática ya que permite diagnosticar enfermedades cerebrales, evaluar su progresión y determinar la eficacia de los nuevos tratamientos para contrarrestarlas. Sin embargo, éste sigue siendo un problema abierto y difícil, ya que el rendimiento de los métodos tradicionales depende de los protocolos y la calidad de las imágenes, los errores de armonización de los datos y las anomalías del cerebro. En esta tesis doctoral, cuestionamos si los métodos de aprendizaje profundo pueden ser utilizados para estimar mejor la atrofia cerebral a partir de imágenes de resonancia magnética. Nuestro trabajo muestra que el aprendizaje profundo puede conducir a un rendimiento de vanguardia en las evaluaciones transversales y competir y superar los métodos tradicionales de cuantificación de la atrofia longitudinal. Creemos que los métodos transversales y longitudinales propuestos pueden ser beneficiosos para la comunidad investigadora y clínica
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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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Einarsdóttir, Hildur. "Imaging of soft tissue tumors /." Stockholm, 2003. http://diss.kib.ki.se/2003/91-7349-647-2/.
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Sharma, Srikanta. "Microultrasound imaging of tissue dysplasia." Thesis, University of Dundee, 2015. https://discovery.dundee.ac.uk/en/studentTheses/ce30ac7f-8d18-464d-bbe5-5e9329ff5ff2.
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The second most common cause of cancer deaths in the developed world is bowel cancer. Improving the ability to detect and classify lesions as early as possible, allows treatment earlier. The work presented in this thesis is structured around the following detailed aims:Development of high frequency, broadband µUS (micro-ultrasound) imaging transducers through optimization of ultra-thinning processes for lithium niobate (LNO) and fabrication of novel ‘mass-spring’ matching layers using carefully controlled vacuum deposition is demonstrated. The effectiveness of this technique was quantified by applying multiple matching layers to 3 mm diameter 45 MHz LNO µUS transducers using carefully controlled vacuum deposition. The bandwidth of single mass-spring layer µUS transducer was measured to be 46% with an insertion loss of 21 dB. The bandwidth and insertion loss of a multiple matching layer µUS transducer was measured to be 59% and 18 dB respectively. The values were compared with an unmatched transducer which had a bandwidth and insertion loss of 28% and 34 dB respectively. All the experimentally measured values were in agreement with unidimensional acoustic model predictions. µUS tools that can detect and measure microscopic changes in precancerous tissue using a mouse small bowel model with an oncogenic mutation was developed. µUS transducer was used to test the hypothesis that the intestinal tissue morphology of WT (wild type) and ApcMin/+ (adenomatous polyposis coli) diverges with progressing age intervals (60, 90 and 120 days) of mice. A high frequency ultrasound scanning system was designed and the experiments were performed ex vivo using a focused 45 MHz, f-# = 2.85, µUS transducer. The data collected by scanning was used to compute the backscatter coefficients (BSC) and acoustic impedance (Z) of WT and ApcMin/+ mice. The 2D and 3D ultrasound images showed that µUS detects polyps < 500 µm in the scan plane. The measured values of BSC and Z showed differences between normal and precancerous tissue. The differences detected in precancerous murine intestine and human tissue using µUS were correlated with high resolution 3D optical imaging. This novel approach may provide a powerful adjunct to screening endoscopy for improved identification and monitoring, allowing earlier treatment of otherwise undetectable lesions.
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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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Killich, Markus. "Tissue Doppler imaging Erstellung von Referenzwerten für tissue velocity imaging, strain und strain rate beim Hund /." [S.l.] : [s.n.], 2006. http://edoc.ub.uni-muenchen.de/archive/00006708.
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Poland, Simon. "Techniques in deep imaging within biological tissue." Thesis, University of Strathclyde, 2006. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=21651.
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This thesis is concerned with the development of low-cost and practical biological optical imaging and diagnosis systems that will allow the user to image and resolve structure deep into biological tissue without the need for physical dissection. Research within this thesis can be divided into two main sections, namely (a) the development of optically sectioning microscopy systems incorporating adaptive optics to compensate for system and specimen induced aberrations, and (b) as an example of biological tissue and disease, the development of dental imaging devices to detect and diagnose dental disease (caries). Section (a) The ability of confocal and multiphoton microscopy techniques to image optical sections deep within biological samples is a major advantage in biology. Unfortunately, as one images deeper within a sample, image degradation increases due to aberrations and scattering. In this investigation, operating a confocal microscope in reflection, a deformable membrane mirror (DMM) was used to counteract for sample aberrations within a closed feedback loop. By selecting various image properties (e. g. brightness, contrast or resolution), various optimisation algorithms were used to improve this property by altering the shape of the DMM and compensate for aberrations. Taking axial and lateral point spread functions (PSFs), the improvement of the system was monitored. The ability of the adaptive optic system to optimise to a particular axial PSF (PSF engineering) was also examined. The use of various algorithms with an adaptive element in a confocal system has been demonstrated to show significant improvement in the axial resolution and signal intensity. While global optimisation algorithms such as the genetic algorithm are more likely to find the global maximum in solution space in comparison to hillclimbing, it usually takes longer to achieve an optimum solution. Particular fitness parameters have shown promise in increasing the effectiveness of the algorithmic search routines. Optimising certain axial PSF components appears to have a detrimental effect on the lateral PSF and resolution. In the situation where the best axial and lateral resolution is required, optimising for intensity appears to show the best all round result. By adapting the axial fitness parameter program, it has been shown that particular desired axial PSF shapes can be reproduced within an aberrated sample. This does appear to have some limitations due to the relative power of the mirror (stroke). Section (b) Using optical techniques, physiological changes associated with the onset of disease in biological tissue can be detected. Taking dental tissue as an example of a highly scattering biological media, a computer model based upon commercially available software was used to theoretically reproduce experimental results taken using a fibre optical confocal system on dental tissue. From simulations, it has been shown that such a system could microscopically measure the optical properties of a caries lesion within dental enamel non-invasively. A system based on the use of structured light to penetrate and quantify early stage dental caries was presented as a possible aid to dentistry. Although the system was able to optically section the carious surface as well as detect inhomogeneities greater than 60μm deep into the tooth sample, more studies must be carried out to assess the limitations of the system. On a macroscopic scale, a cost effective system known as near-infrared Lateral Illumination (L. I.) (which is based on transillumination techniques) was presented. In a preliminary study involving 15 ex-in vivo adult pre-molars and molars at various stages of dental decay, L. I. was shown to be the most effective occlusal caries diagnosis system when compared to some techniques currently available and in development.
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Lapp, Sarah Julia. "Bioluminescence Imaging Strategies for Tissue Engineering Applications." Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/32338.
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In vitro differentiation of stem cells in biocompatible scaffolds in a bioreactor is a promising method for creating functional engineered tissue replacements suitable for implantation. Basic studies have shown that mechanical, chemical, and pharmaceutical stimuli enhance biological functionality of the replacement as often defined by parameters such as cell viability, gene expression, and protein accumulation. Most of the assays to evaluate these parameters require damage or destruction of the cell-scaffold construct. Therefore, these methods are not suitable for monitoring the development of a functional tissue replacement in a spatial and temporal manner prior to implantation. Bioluminescence imaging is a technique that has been utilized to monitor cell viability and gene expression in various in vivo applications. However, it has never been applied in an in vitro setting for the specific purpose of evaluating a cell-scaffold construct.
This research describes the design of flow perfusion bioreactor system suitable for bioluminescence imaging. In the first experimental chapter, the system was tested using MC3T3-E1 cells transfected with a constitutive bioluminescent reporter. It was found that bioluminescence imaging was possible with this system. In the second experimental chapter, MC3T3-E1 cells transfected with BMP-2 linked bioluminescence reporter were cultured by flow perfusion for a period of 11 days. Bioluminescence was detectable from the cells starting at day 4, while peaking in intensity between days 7 and 9. Further, it was also found that bioluminescence occurred in distinct regions within the scaffold. These results indicate that these strategies may yield information not available with current assays.Master of Science
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Unnersjö-Jess, David. "High-resolution imaging of kidney tissue samples." Licentiate thesis, KTH, Cellulär biofysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-207577.
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The kidney is one of the most important and complex organs in the human body, filtering hundreds of litres of blood daily. Kidney disease is one of the fastest growing causes of death in the modern world, and this motivates extensive research for better understanding the function of the kidney in health and disease. Some of the most important cellular structures for blood filtration in the kidney are of very small dimensions (on the sub-200 nm scale), and thus electron microscopy has been the only method of choice to visualize these minute structures. In one study, we show for the first time that by combining optical clearing with STED microscopy, protein localizations in the slit diaphragm of the kidney, a structure around 75 nanometers in width, can now be resolved using light microscopy. In a second study, a novel sample preparation method, expansion microscopy, is utilized to physically expand kidney tissue samples. Expansion improves the effective resolution by a factor of 5, making it possible to resolve podocyte foot processes and the slit diaphragm using confocal microscopy. We also show that by combining expansion microscopy and STED microscopy, the effective resolution can be improved further. In a third study, influences on the development of the kidney were studied. There is substantial knowledge regarding what genes (growth factors, receptors etc.) are important for the normal morphogenesis of the kidney. Less is known regarding the physiology behind how paracrine factors are secreted and delivered in the developing kidney. By depleting calcium transients in explanted rat kidneys, we show that calcium is important for the branching morphogenesis of the ureteric tree. Further, the study shows that the calcium-dependent initiator of exocytosis, synaptotagmin, is expressed in the metanephric mesenchyme of the developing kidney, indicating that it could have a role in the secretion of paracrine growth factors, such as GDNF, to drive the branching.QC 20170523
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Sahalan, Mariaulpa. "Diffusion-weighted Imaging of Lymph Node Tissue." Thesis, The University of Sydney, 2018. http://hdl.handle.net/2123/20070.
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Purpose: The study investigates the hypothesis of clinically observed decreased apparent diffusion coefficient (ADC) of cancerous lymph nodes can be attributed to increased cellularity. The study characterises the mean diffusivity (MD) of lymph node sub-structures and investigates correlation between MD and cellularity metrics. The study also investigates the theoretical information content of single and multi-biophysical models. Methods:. A 3 mm diameter core sample was extracted from a formalin fixed lymph node tissue post-surgery and imaged using 9.4T and 16.4T Bruker MRI system. Samples were sectioned and stained with haematoxylin and eosin (H&E). Diffusion tensor model was fitted voxelwise and MD values were computed using Matlab. Cellularity metrics includes measurement of nuclear count and nuclear area. Eleven models with combinations of isotropic, anisotropic, and restricted components were tested for diffusion modelling and ranked using the Akaike information criterion (AIC). Results: The findings showed distinct diffusivities of lymph node sub-structures (capsule and parenchyma). Parenchyma in normal lymph node tissues had higher MD (0.71 ± 0.17 µm2/ms) than metastatic parenchyma (0.52 ± 0.08 µm2/ms) and lymphoma (0.47 ± 0.19 µm2/ms). No correlation were observed between MD and nuclear count (r = 0.368) and nuclear area (r = 0.368) respectively at 95 % confidence intervals. The single biophysical models (ADC and DTI) were ranked lowest by AIC. Multi-biophysical models consist of anisotropic and restricted diffusion (Zeppelin-sphere, Ball-stick-sphere, and Ball-sphere) were ranked highest in the majority of voxels of the tissue samples. Conclusion: A distinct diffusivity value were found in lymph node sub-structures with no correlation to cellularity. Multi-biophysical models were ranked highest and extract more information from the measurement data than simple single biophysical models.
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Martinini, Filippo. "Deep Neural Recovery For Compressed Imaging." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/22431/.
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One of the biggest problem of MRI is its long scan time. To speed up the acquisition is possible to reduce the acquired points and reconstruct the missing ones after the acquisition. This work is based on a novel approach called LOUPE that tackles at same time the problem of reconstruction and the problem of finding the best under-sampling pattern. We contribute by adding some improvements to LOUPE. We introduce a regularization term, called "Flashback" that weights the difference of the under-sampled input with respect to its reconstructed version and improves the whole training performances. We show how Flashback can be also used as self-assessment to predict the reconstruction error of every scan at inference time. We introduce a method called "Back to the Future" that improves performances by swopping the acquired reconstructed frequency values with the original acquired frequency values. We introduce a layer called Trainable Inverse Fourier Transform (TIFT) that enables the classic layer for Inverse Fourier Transform to be trainable. Finally, we introduce "Prancing Pony", a method that automatically rises the slope of the sigmoid that produces the mask values, to automatically find its best value.
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Ford-Dunn, Helen. "Genetic modification of neural tissue for xenotransplantation." Thesis, University of Oxford, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.404117.
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Stabenfeldt, Sarah Elizabeth. "Bioactive thermoresponsive hydrogels for neural tissue engineering." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/26680.
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Thesis (Ph. D.)--Biomedical Engineering, Georgia Institute of Technology, 2008.Committee Chair: LaPlaca, Michelle; Committee Member: Bellamkonda, Ravi; Committee Member: Garcia, Andres; Committee Member: Hochman, Shawn; Committee Member: Wang, Yadong. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Hoyt, Kenneth Leon Forsberg Flemming. "Spectral strain estimation techniques for tissue elasticity imaging /." Philadelphia, Pa. : Drexel University, 2005. http://dspace.library.drexel.edu/handle/1860/504.
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Sikdar, Siddhartha. "Ultrasonic imaging of flow-induced vibrations in tissue /." Thesis, Connect to this title online; UW restricted, 2005. http://hdl.handle.net/1773/6100.
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Hilton, Judy A. "An Acoustic Imaging System for Soft Tissue Stress." Fogler Library, University of Maine, 2005. http://www.library.umaine.edu/theses/pdf/HiltonJA2005.pdf.
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Bálint, Péter Vince. "Ultrasound imaging in joint and soft tissue inflammation." Thesis, University of Glasgow, 2002. http://theses.gla.ac.uk/2266/.
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The use of ultrasound as an extended and more objective investigation performed as an extension of physical examination has a potential role in studying inflammation in different rheumatic diseases such as rheumatoid arthritis (RT) and spondylarthropathy (SpA). Rheumatoid arthritis is a chronic disease causing joint inflammation and destruction. Metacarpophalangeal (MCP) joint involvement is one of the earliest and most permanent signs of RA. US has been used to detect synovitis and erosions in MCP joints with high accuracy when compared to X-ray and magnetic resonance imaging (MRI). In RA joints, power Doppler has been used to detect increased blood flow as a potential sign of inflammation but grey-scale and power Doppler ultrasonography was not compared to another method to detect increased blood flow in MCP joints. After RA the next most common inflammatory group of diseases are the seronegative spondylarthropathies. In SpA joint inflammation and ankylosis occur in addition to periarticular enthesitis, which is one of the major hallmarks of the disease and has been poorly studied by ultrasonography. In order to reduce observer variation in musculoskeletal ultrasound examination to the level of other imaging methods it is necessary to avoid direct contact between the observer and the subject. This problem has been addressed in the aerospace industry and led to the development of air-coupled non-destructive testing. Air-coupled ultrasonography has the potential in medial imaging to exclude observer variation if it is able to depict human anatomy. There are currently no data regarding airborne ultrasound in the musculoskeletal ultrasound literature.
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Li, Teng. "Advanced Photoacoustic Measurement and Imaging in Biological Tissue." Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.506584.
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Tillberg, Paul W. "Expansion microscopy : improving imaging through uniform tissue expansion." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/106094.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 70-76).
Until the past decade, optical microscopy of biological specimens was strongly limited by diffraction and scattering, affecting imaging resolution and depth, respectively. Now, numerous methods are available to overcome each of these limitations, but sub-diffraction limited resolution imaging over large volumes of scattering tissue is still a challenge. This work concerns the development of a new method, Expansion Microscopy (ExM) for achieving effect sub-diffraction-limited optical images in biological specimens. In ExM, the specimen is embedded in a swellable gel material to which fluorescent probes are chemically anchored. The embedded tissue is strongly digested so that it will not hinder uniform expansion driven by the gel. The gel with embedded, fragmented tissue is washed in water, triggering expansion of around 4-fold in each dimension. A variant of the method, ExM with Protein Retention (proExM) is presented that allows proteins themselves, rather than fluorescent probes, to be anchored by a small molecule cross-linker to the gel, so that the method may be carried out entirely with commercial components and standard antibodies.
by Paul W. Tillberg.
Ph. D.
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Laurens, Ediuska V. "Imaging of Tyramine-Substituted Hydrogels for Tissue Replacement." Cleveland State University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=csu1265639619.
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Penmatsa, Madhuri Krishna. "Infrared Spectral Imaging Analysis Of Cartilage Repair Tissue." Master's thesis, Temple University Libraries, 2011. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/124100.
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BioengineeringM.S.
Articular cartilage is a homogenous tissue that provides frictionless movement between joints while withstanding repetitive physical stress. Once degenerated as a result of osteoarthritis or an injury, it has very limited capacity for self-repair. Recent research has focused on developing many new technologies for cartilage repair. The successful application of these strategies is limited in part to lack of techniques to evaluate tissue response to interventions. Assessment of the structural and molecular changes in the primary cartilage components, proteoglycan (PG) and collagen is critical to evaluate progress of the repair tissue. In the present study Fourier transform infrared imaging spectroscopy (FT-IRIS) was utilized to evaluate molecular changes in normal and degenerated cartilage in a rabbit model of repair. Parameters such as collagen integrity, type II collagen and proteoglycan are important factors in determining the biomechanical properties of articular cartilage, and are likely as important in determining functional competence of repair tissue. Histological evaluations are considered to be one of the most important methods for determining the quality of the repair tissue, but still do not predict clinical outcome. It is possible that a new tissue scoring system that considers molecular parameters in the repair tissue, along with the histological outcomes, will better predict clinical success of repair. The main goal of this study is to assess correlations between histological grading, immunohistochemical assessments of type I and II collagen, and FT-IRIS parameters, in cartilage repair tissue in a rabbit model. These data will provide the basis for a novel tissue scoring system using FT-IRIS parameters alone, or in conjunction with histological and immunohistochemical outcomes. This could yield better correlations with clinical outcomes that may lead to optimization of the cartilage repair process.
Temple University--Theses
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Hill, Esme. "Perfusion imaging and tissue biomarkers for colorectal cancer." Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:4a309265-6f27-4839-9259-f19cf9648c2d.
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Background: Systemic chemotherapy and radiotherapy play an important role in the treatment of colorectal cancer. Tumour perfusion and oxygenation is known to influence radiosensitivity and chemosensitivity. In this thesis, I propose that the evaluation of changes in tumour perfusion using perfusion CT (pCT) and dynamic contrast-enhanced (Dce) MRI can guide the rational sequencing of drugs and radiation. Methods: Dce-MRI and pCT scans were incorporated into a clinical trial of hypofractionated pelvic radiotherapy and nelfinavir in 10 patients with rectal cancer. Toxicity and tissue biomarkers (tumour cell density, microvessel density, CAIX, HIF1-alpha, phospho-Akt and phospho-PRAS40) were evaluated. pCT liver scans were incorporated into an imaging study in patients with colorectal liver metastases randomised to receive either oxaliplatin/ 5FU chemotherapy or oxaliplatin/ 5FU chemotherapy plus selective internal radiotherapy. Results: After 7 days of nelfinavir concurrent with hypo-fractionated pelvic radiotherapy, there was a mean 42% increase in median Ktrans (P=0.03, paired t test) on Dce-MRI and a median 30% increase in mean blood flow on pCT (P=0.028, Wilcoxon Rank Sum), although no statistically significant changes in perfusion parameters were demonstrated after 7 days of nelfinavir prior to radiotherapy. The feasibility of evaluating tumour cell density in rectal biopsies before and after radiotherapy and a radiosensitising drug as an early endpoint of response was demonstrated. In patients with colorectal liver metastases who received oxaliplatin and modified de Gramont chemotherapy alone, after 4 cycles of chemotherapy, a 28% decrease in the mean hepatic arterial fraction was observed (P=0.018, paired t test). Between pCT scans 2 days before SIRT and 39-47 days following SIRT and continued 2-weekly chemotherapy, there was a mean 62% (P=0.009) reduction in Blood Flow and 61% (P=0.006) reduction in Blood Volume (paired t test). Conclusions This research does not support the hypothesis that nelfinavir before radiotherapy improves blood flow to human rectal cancer. Increases in rectal tumour perfusion during radiotherapy and concurrent nelfinavir are likely to be primarily explained by the acute biological effects of radiation. Four or more cycles of oxaliplatin and modified de Gramont chemotherapy may result in changes in tumour perfusion of colorectal liver metastases which would be detrimental to subsequent radiotherapy. Selective internal radiotherapy resulted in substantial reductions in tumour perfusion 39-47 days after the treatment. Perfusion imaging can be used to detect changes in tumour perfusion in response to radiotherapy and systemic therapy which have implications for the sequencing of therapies.
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Wekselblatt, Joseph. "Imaging Neural Circuits Underlying Learning and Behavior." Thesis, University of Oregon, 2018. http://hdl.handle.net/1794/23176.
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Sensory perception is context dependent and is likely modulated by task demands, learning and engagement to best serve specific goals of the organism. Sensory-driven behaviors also engage a cascade of cortical regions to process sensory input and generate motor output. To investigate the temporal dynamics of neural activity at this global scale, we have improved and integrated tools to perform functional imaging across large areas of cortex using a transgenic mouse expressing a fluorescent activity sensor. Imaging during an orientation discrimination task reveals a progression of activity in different cortical regions associated with different phases of the task. After cortex-wide patterns of activity are determined, we demonstrate the ability to select a region that displayed conspicuous responses for two-photon microscopy, and find that activity in populations of individual neurons in that region correlates with locomotion in trained mice.
We also found that learning a visual discrimination reduced population activity in visual cortex. To further investigate this phenomenon, we used two-photon microscopy to image mice before or after they had learned a visual discrimination. We find that excitatory neurons in layer 2/3 show striking diversity in their temporal dynamics during the behavior and classify them into transient, sustained, and suppressed groups. Notably, these groups exhibit different visual tuning and modulation by locomotion. The functionally defined cell classes are also differentially modulated by training condition: showing both a cell class specific decrease in fraction responsive to visual stimuli after learning, and an increase in modulation by task engagement specific to trained animals. The characterization of pyramidal neuron subtypes in layer 2/3 of V1, and quantification of their distinct changes over learning, provides new insight into the circuit elements and pathways that enable goal-directed sensory processing.
This dissertation includes published and unpublished co-authored material. This dissertation also includes four supplemental movies related to functional imaging techniques described in chapter II.2019-01-09
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O'Brien, David Patrick. "Micromachined microelectrode arrays for stimulation of neural tissue." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/14993.
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Steinmeyer, Joseph D. (Joseph Daly). "Automation of single-cell techniques in neural tissue." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/90004.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 125-140).
The highly heterogeneous nature of cells in the context of native tissue environments necessitates the development of tools and techniques that can manipulate and analyze samples with single-cell resolution. While the past decades have seen significant progress in analyzing individual cells in tissue, both electrically and morphologically, the ability to genetically manipulate and biochemically analyze such cells in a high-throughput manner has seen only limited advances, and therefore a significant technological gap in accessing cells with single-cell specificity in tissue remains. We present a system design and workflow that fills in this gal) in technology through the implementation of precision automation and redesign of standard biological techniques, resulting in greatly improved throughput while maintaining single-cell accuracy and precision. This thesis comprises three parts: First we discuss the design and implementation of an expandable computer-controlled automation system enabling the rapid maneuvering and targeting of inicropipettes within tissue environments as well as a methodology for cleaning and reuse of these micropipettes to enable significant gains in throughput. Second we apply this automation to transfecting neurons in brain slices with DNA and RNA for subsequent analysis with greater throughput than previous methods. Third, we apply our automation to collecting the contents of single neurons embedded in relevant tissue environments for molecular analysis. The work presented greatly improves the throughput of traditional single-cell methods of transfection and cell-sampling by between one and two orders of magnitude and fills in a gap in the workflow of the rapidly expanding field of single-cell analysis.
by Joseph D. Steinmeyer.
Ph. D.
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Stopek, Joshua B. "Bipolymer-microglia cell compositions for neural tissue repair." [Gainesville, Fla.] : University of Florida, 2003. http://purl.fcla.edu/fcla/etd/UFE0001105.
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Barnes, Samesha Rosánne. "Injectable biopolymer gel compositions for neural tissue repair." [Gainesville, Fla.] : University of Florida, 2009. http://purl.fcla.edu/fcla/etd/UFE0024088.
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Hofstad, Erlend Fagertun. "Ultrasound Contrast Imaging - Improved Tissue Suppression in Amplitude Modulation." Thesis, Norwegian University of Science and Technology, Department of Electronics and Telecommunications, 2006. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-9316.
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The ability to image myocardial perfusion is very important in order to detect coronary diseases. GE Vingmed Ultrasound uses contrast agent in combination with a pulse inversion (PI) technique to do the imaging. But this technique does not function sufficiently for all patients. Therefore have other techniques been tested out, including transmission of pulses with different amplitude (AM), to enhance the nonlinear signal from contrast bubbles. But a problem achieving sufficient cancellation of linear tissue signal is a feebleness of the method. In this diploma work has an effort been put into enhancing the tissue suppression in amplitude modulation. First the source of the lack of suppression was searched for by measuring electrical and acoustical pulses. The further examination revealed a dissymmetry in between pulses of different amplitude. To reduce this error were several attempts to make a compensation filter performed, which finally resulted in a filter created of echo data acquired from a tissue mimicking phantom. The filter was furthermore tested out on a flow phantom to see how it affected the signal from tissue and contrast bubbles, compared to the former use of a constant instead of the filter. The comparison showed 1.5-3.2 dB increase in tissue suppression (TS). But unfortunately did the filtering process slightly reduce the contrast signal as well, which resulted in a smaller increase of Contrast-to-Tissue-Ratio (CTR) than TS; 1.0-2.8 dB. During the work was the source of another problem concerning tissue suppression discovered. In earlier work by the author cite{prosjekt} the experimental results suffered from low TS around the transmitted frequency, which was found inexplicable at that time. This problem was revealed to be caused by reverberations from one pulse, interfering with the echoes from the next pulse. The solution suggested in this thesis is to transmit pulses in such a way that every pulse used to create an image has a relatively equal pulse in front. For instance, if a technique employs two pulses to create an image, and the first has half the amplitude and opposite polarity of the second. Then, to eliminate the reverberations must the first imaging pulse have a pulse in front which has half the amplitude and opposite polarity of the pulse in front of the second imaging pulse.
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Ke, Meng-Tsen. "Optical clearing and deep-tissue fluorescence imaging using fructose." 京都大学 (Kyoto University), 2014. http://hdl.handle.net/2433/188839.
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Pašović, Mirza. "Tissue harmonic reduction : application to ultrasound contrast harmonic imaging." Thesis, Lyon 1, 2010. http://www.theses.fr/2010LYO10060.
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Les agents de contraste sont de petites bulles qui répondent non linéairement lorsqu’ils sont exposés à ultrasons. La réponse non-linéaire donne la possibilité d’images échographiques harmoniques qui a beaucoup d’avantages sur l’imagerie fondamentale. Toutefois, afin d’accroître l’échographie de contraste d’imagerie harmonique de performance nous devons d’abord comprendre la propagation non linéaire d’ultrasons. La non-linéarité du milieu déforme l’onde qui se propage, tels que les harmoniques commencent à se développer. La théorie qui a été prévue est la mise en œuvre, qui a permis une nouvelle méthode de modélisation de propagation des ultrasons non-linéaire. La connaissance acquise au cours de ce processus a été utilisée pour construire un deuxième signal à composantes multiples pour la réduction des harmoniques générées en raison des non-linéarités des tissus. En conséquence, la détection d’agents de contraste ultrasonore aux harmoniques a été augmentée. Une puissante technique d’imagerie échographique (Pulse inversion) a été renforcée avec le deuxième signal pour la réduction des harmoniques. Qu’est-ce qui a été appris pendant l’investigation : le pulse inversion technique a donné une nouvelle phase codée, appelée inversion de seconde harmonique. En outre, il a été noté que pour différents types de médias le niveau de distorsion de l’impulsion à ultrasons est différent. Cela dépend en grande partie du paramètre non linéaire B / A. Les travaux sur ce paramètre n’a pas été fini, mais il est quand même important de continuer dans cette direction puisque B / A imagerie avec des agents de contraste ultrasonore a beaucoup de potentielUltrasound contrast agents are small micro bubbles that respond nonlinearly when exposed to ultrasound wave. The nonlinear response gives possibility of harmonic ultrasound images which has many advantages over fundamental imaging. However, to increase ultrasound contrast harmonic imaging performance we must first understand nonlinear propagation of ultrasound wave. Nonlinear propagation distorts the propagating wave such that higher harmonics appear as the wave is propagating. The theory that was laid down, was allowed implementing a new method of modelling nonlinear ultrasound propagation. The knowledge obtained during this process was used to construct a multiple component second harmonic reduction signal for reduction of their harmonics generated due to the tissue nonlinearities. As a consequence detection of ultrasound contrast agents at higher harmonics was increased. Further more, a powerful ultrasound imaging technique called Pulse Inversion, was further enhanced with multiple component second harmonic reduction signal. What was learned during investigation of the Pulse Inversion, technique lead to a new phase coded ultrasound contrast harmonic method called second harmonic inversion;. Also it was noted that for different type of media the level of distortion of ultrasound pulse is different. It depends largely on the nonlinear parameter B / A. Although the work on this parameter has not been finished it is very important to continue in this direction since B / A imaging with ultrasound contrast agents has a lot of potential
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Walker, Paul Michael. "A test material for tissue characterization in N.M.R. imaging." Thesis, Imperial College London, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.338275.
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Utting, Jane Francis. "Magnetic resonance imaging of tissue microcirculation in experimental studies." Thesis, University College London (University of London), 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.272348.
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Winder, Robert John. "Medical imaging : tissue volume measurement & medical rapid prototyping." Thesis, University of Ulster, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.399689.
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Lee, Z. S. "Towards real-time imaging of strain in soft tissue." Thesis, University of Sheffield, 2018. http://etheses.whiterose.ac.uk/20003/.
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Meeus, Emma Maria. "Investigation of tissue microenvironments using diffusion magnetic resonance imaging." Thesis, University of Birmingham, 2018. http://etheses.bham.ac.uk//id/eprint/8372/.
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Diffusion-weighted magnetic resonance imaging (DW-MRI) has rapidly become an important part of cancer patient management. In this thesis, challenges in the analysis and interpretation ofDW-MRI data are investigated with focus on the intravoxel incoherent motion (IVIM) model, and its applications to childhood cancers. Using guidelines for validation of potential imaging biomarkers, technical and biological investigation of IVIM was undertaken using a combination of model simulations and in vivo data. To reduce the translational gap between the research and clinical use of IVIM, the model was implemented into an in-house built clinical decision support system. Technical validation was performed with assessment of accuracy, precision and bias of the estimated IVIM parameters. Best performance was achieved with a constrained IVIM fitting approach. The optimal use of b-values was dependent on the tissue characteristics and a compromise between bias and variability. Reliable data analysis was strongly dependent on the data quality and particularly the signal-to-noise ratio. IVIM perfusion fraction (j) was generally found to correlate with dynamic susceptibility contrast imaging derived cerebral blood volume. IVIM-f also presented as a potential diagnostic biomarker in discriminating between malignant retroperitoneal tumour types. Overall, the results encourage the use of IVIM parameters as potential imaging biomarkers.
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Zhang, Yu. "Hyaluronan Based Biomaterials with Imaging Capacity for Tissue Engineering." Doctoral thesis, Uppsala universitet, Institutionen för kemi - Ångström, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-300799.
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This thesis presents the preparation of hyaluronan-based biomaterials with imaging capability and their application as scaffolds in tissue engineering. First, we have synthesized HA derivatives functionalized with different chemoselective groups. Then, functional ligands with capacities for hydrophobic drug loading, imaging, and metal ion coordination were chemically conjugated to HA by chemoselective reactions with these groups. An injectable in situ forming HA hydrogel was prepared by hydrazone cross-linking between hybrid iron-oxide nanogel and HA-aldehyde (paper-I). The degradation of this hydrogel could be monitored by MRI and UV-vis spectroscopy since it contained iron oxide as a contrast agent and pyrene as a fluorescent probe. Additionally, this hydrogel has a potential for a delivery of hydrophobic drugs due to its pyrene hydrophobic domains. The degradation study showed that degradability of the hydrogel was correlated with its structure. Based on the obtained results, disulfide cross-linked and fluorescently labeled hydrogels with different HA concentration were established as a model to study the relationship between the structure of the hydrogel and its degradability (paper-II). We demonstrated that disulfide cross-linked HA hydrogel could be tracked non-invasively by fluorescence imaging. It was proved that the in vivo degradation behavior of the hydrogel is predictable basing on its in vitro degradation study. In paper-III, we developed a disulfide cross-linked HA hydrogel for three-dimensional (3D) cell culture. In order to improve cell viability and adhesion to the matrix, HA derivatives were cross-linked in the presence of fibrinogen undergoing polymerization upon the action of thrombin. It led to the formation of an interpenetrating double network (IPN) of HA and fibrin. The results of 3D cell culture experiments revealed that the IPN hydrogel provides the cells with a more stable environment for proliferation. The results of the cellular studies were also supported by in vitro degradation of IPN monitored by fluorescence measurements of the degraded products. In paper-IV, the effect of biomineralization on hydrogel degradation was evaluated in a non-invasive manner in vitro. For this purpose, two types of fluorescently labeled hydrogels with the different ability for biomineralization were prepared. Fluorescence spectroscopy was applied to monitor degradation of the hydrogels in vitro under two different conditions in longitudinal studies. Under the supply of Ca2+ ions, the BP-modified hydrogel showed the tendency to bio-mineralization and reduction of the rate of degradation. Altogether, the performed studies showed the importance of imaging of hydrogel biomaterials in the design of optimized scaffolds for tissue engineering.
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Shukla, Vipul. "Intravital Imaging of Borrelia burgdorferi in Murine Skin Tissue." University of Toledo Health Science Campus / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=mco1271697663.
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Zhao, Mingjun. "NONINVASIVE MULTIMODAL DIFFUSE OPTICAL IMAGING OF VULNERABLE TISSUE HEMODYNAMICS." UKnowledge, 2019. https://uknowledge.uky.edu/cbme_etds/58.
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Measurement of tissue hemodynamics provides vital information for the assessment of tissue viability. This thesis reports three noninvasive near-infrared diffuse optical systems for spectroscopic measurements and tomographic imaging of tissue hemodynamics in vulnerable tissues with the goal of disease diagnosis and treatment monitoring. A hybrid near-infrared spectroscopy/diffuse correlation spectroscopy (NIRS/DCS) instrument with a contact fiber-optic probe was developed and utilized for simultaneous and continuous monitoring of blood flow (BF), blood oxygenation, and oxidative metabolism in exercising gastrocnemius. Results measured by the hybrid NIRS/DCS instrument in 37 subjects (mean age: 67 ± 6) indicated that vitamin D supplement plus aerobic training improved muscle metabolic function in older population. To reduce the interference and potential infection risk on vulnerable tissues caused by the contact measurement, a noncontact diffuse correlation spectroscopy/tomography (ncDCS/ncDCT) system was then developed. The ncDCS/ncDCT system employed optical lenses to project limited numbers of sources and detectors on the tissue surface. A motor-driven noncontact probe scanned over a region of interest to collect boundary data for three dimensional (3D) tomographic imaging of blood flow distribution. The ncDCS was tested for BF measurements in mastectomy skin flaps. Nineteen (19) patients underwent mastectomy and implant-based breast reconstruction were measured before and immediately after mastectomy. The BF index after mastectomy in each patient was normalized to its baseline value before surgery to get relative BF (rBF). Since rBF values in the patients with necrosis (n = 4) were significantly lower than those without necrosis (n = 15), rBF levels can be used to predict mastectomy skin flap necrosis. The ncDCT was tested for 3D imaging of BF distributions in chronic wounds of 5 patients. Spatial variations in BF contrasts over the wounded tissues were observed, indicating the capability of ncDCT in detecting tissue hemodynamic heterogeneities. To improve temporal/spatial resolution and avoid motion artifacts due to a long mechanical scanning of ncDCT, an electron-multiplying charge-coupled device based noncontact speckle contrast diffuse correlation tomography (scDCT) was developed. Validation of scDCT was done by imaging both high and low BF contrasts in tissue-like phantoms and human forearms. In a wound imaging study using scDCT, significant lower BF values were observed in the burned areas/volumes compared to surrounding normal tissues in two patients with burn. One limitation in this study was the potential influence of other unknown tissue optical properties such as tissue absorption coefficient (µa) on BF measurements. A new algorithm was then developed to extract both µa and BF using light intensities and speckle contrasts measured by scDCT at multiple source-detector distances. The new algorithm was validated using tissue-like liquid phantoms with varied values of µa and BF index. In-vivo validation and application of the innovative scDCT technique with the new algorithm is the subject of future work.
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Zhu, Danyi. "Imaging Fast Neural Activities with Electrical Impedance Tomography." Thesis, University of Sydney, 2020. https://hdl.handle.net/2123/23477.
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In this thesis we show impedance imaging may be used to measure neuronal activity at various stages of the visual system. Electrical Impedance Tomography (EIT) is a medical imaging technique that reconstructs conductivity distribution of an object using impedance measurement. EIT enables neuronal depolarisation to be imaged at high spatial-temporal resolution in rat cerebral cortex and sciatic nerve. Moreover it holds therapeutic potentials of localising epileptic foci and detecting cortical stroke in clinical diagnosis. The overall aim of this work is to image fast neural activities in visual system using EIT. In the course of the investigation, a computational model of retinal stimulation and impedance measurement was developed to characterise the mechanism of neuronal impedance change in retinal ganglion cells. Base on the results derived from mathematical modelling, we set up experiment paradigm of recording impedance change from isolated mouse retina. Furthermore, we developed finite element model to evaluated feasibility of imaging visual thalamic bodies with EIT by incorporating realistic mesh and electrophysiological recording from marmoset. The outcome was encouraging as we observed light evoked spike trains and impedance changes in dark adapted retina, which in agreement with our simulated prediction. The result presented in this dissertation was the first attempt of acquiring neural impedance recording from retinal tissue to our knowledge, which may inspire EIT into sub-millimetre imaging at cellular level. This study implies EIT has the possibility of yielding novel approaches to image neuronal activities in visual neuroscience.
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Roy, Ranadhir. "Image reconstruction from light measurements on biological tissue." Thesis, University of Hertfordshire, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.338567.
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Segura, Carlos Alejandro. "Development of an optrode for characterization of tissue optical properties at the neural tissue-electrode interface." Thesis, Boston University, 2014. https://hdl.handle.net/2144/21118.
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Thesis (M.Sc.Eng.)The use of implantable neural probes has become common, both for stimulation and recording, and their applications range from chronic pain treatment to implementation of brain machine interfaces (BMI). Studies have shown that signal quality of implanted electrodes decays over time mainly due to the immune response. Characterization of the tissue-electrode interface is critical for better understanding of the physiological dynamics and potential performance improvement of the electrode itself and its task. This work describes the fabrication of an implantable electrode with optical measurement capabilities for providing means to characterize the tissue-electrode interface using optical spectroscopy. The electrode has a set of waveguides embedded in its shanks, which are used to inject white light into tissue and then collect the light reflected from the tissue surrounding the shanks. The collected light was analyzed with a spectrometer and the spectra processed to detect changes in optical properties, information that allows to track physiological changes. It is believed that the immune response can be correlated to changes in scattering as more cells are recruited to the injury site. The increased cell density in local injury/implantation sites increases the amount of scattering due to the increased number of cell nuclei and membranes that light encounters in its path. Investigation of scattering and absorption coefficients in such interface and their change over time can provide useful data for modeling and determining physiological parameters like blood oxygenation while the actual shape of the acquired spectra might highlight particular phenomena that can be indicative of scaring process or hemorrhaging. Validation of this system was done using optical phantoms based on polystyrene spheres and solutions with various concentrations of fat emulsion, which yielded scattering coefficients similar to those of brain tissue. Results suggest that the developed optrodes are able to detect differences between samples with different scattering coefficients. Improvements of fabrication process are discussed based on experimental results and future work includes attempting to perform fluorescence measurements of voltage reporters for optogenetic applications. The ultimate goal of this project was to create a novel device that is capable of satisfying the unmet need of tissue characterization at the implanted electrode interface as well as a tool for the optogenetics field suitable for greater depths than those a microscope can achieve.
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Aldoori, Ayat Dhia. "Elucidation of signaling mediators between adipose and neural tissue." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1407845819.
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