Dissertations / Theses on the topic 'Brain – Spectroscopic imaging'
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1
Parikh, Jehill. "Measurement of brain temperature using magnetic resonance spectroscopic imaging." Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/8082.
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The study of brain temperature is important for a number of clinical conditions such as stroke, traumatic brain injury, schizophrenia and birth asphyxia (for neonates). A direct method to estimate brain temperature non-invasively will allow assessment of brain thermoregulation and its variation in clinical conditions. Magnetic resonance imaging is a powerful technique widely used for diagnosis of a range of neurological conditions. All magnetic resonance procedures involve manipulation of the hydrogen nuclei in the water molecules of the human body. The resonance frequency of the water molecules is temperature dependent, thus MR thermometry is a powerful tool for non-invasive temperature measurement. Using internal reference MR spectroscopic imaging (MRSI), absolute brain temperature maps can be estimated. However a number of temperature independent factors influence MRSI data acquisition, thus a thorough validation is necessary and is the focus of this PhD study. In this PhD study using phantom (test object) studies it was shown that optimization of the MRSI pulse sequence is necessary to reduce systematic error in temperature maps and extensive in-vitro validation of MRSI temperature mapping was performed. A custom made temperature-controlled phantom was designed for this purpose and is presented in this thesis. MRSI data acquired from healthy (young and elderly) volunteers was employed to assess regional brain temperature variations and repeatability. Finally, the feasibility of employing fast echo planar spectroscopic imaging for volumetric MRSI temperature mapping will be presented in this thesis.
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Wild, James Michael. "Proton magnetic resonance spectroscopic imaging of the human brain." Thesis, University of Edinburgh, 1998. http://hdl.handle.net/1842/22742.
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Over the last ten years proton NMR spectroscopy has been performed on clinical MRI scanners using single voxel localisation and spectroscopic imaging sequences. In this work inner volume excitation of a transverse imaging plane within the brain has been used to obtain single slice spectroscopic images of proton metabolites. The existing image processing protocols used to construct the metabolite images were improved and optimised so as to give as accurate a picture of metabolite distribution as possible. Inaccuracy in these images can be introduced by the excitation profile of the radio frequency pulses used in inner volume excitation. A new normalisation technique is proposed which will remove these inaccuracies enabling more reliable quantification of metabolite concentrations. Of particular importance in stroke is the metabolite lactate, elevated levels of which are symptomatic with the conditions of anaerobic glycolysis that are thought to precede infarction. The signal from lactate is often obscured by lipid and macro-molecule resonances in the same frequency range. Lactate editing sequences compatible with the hardware capabilities of the scanner and spectroscopic imaging sequences were investigated for viability in-vivo. Using two different editing sequences lactate editing was performed successfully in vitro and in vivo. In-vivo results are presented from a study of 40 stroke patients and a smaller pilot study of 8 head injury patients. These patients were drawn from the Lothian Stroke Register as part of the Clinical Research Initiative (CRI) in stroke and head injury being co-ordinated at the Western General Hospital, Edinburgh. To our knowledge this is the largest proton spectroscopic study of acute stroke patients and as such should have a significant bearing in analysing the physiological implications of the disease.
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Kok, Trina. "Magnetic resonance spectroscopic imaging with 2D spectroscopy for the detection of brain metabolites." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/78450.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2012.Cataloged from PDF version of thesis. Page 94 blank.
Includes bibliographical references (p. 87-93).
While magnetic resonance imaging (MRI) derives its signal from protons in water, additional biochemical compounds are detectable in vivo within the proton spectrum. The detection and mapping of these much weaker signals is known as magnetic resonance spectroscopy or spectroscopic imaging. Among the complicating factors for this modality applied to human clinical imaging are limited chemical-shift dispersion and J-coupling, which cause spectral overlap and complicated spectral shapes that limit detection and separation of brain metabolites using MR spectroscopic imaging (MRSI). Existing techniques for improved detection include so-called 2D spectroscopy, where additional encoding steps aid in the separation of compounds with overlapping chemical shift. This is achieved by collecting spectral data over a range of timing parameters and introducing an additional frequency axis. While these techniques have been shown to improve signal separation, they carry a penalty in scan time that is often prohibitive when combined with MRSI. Beyond scan time constraints, the lipid signal contamination from the subcutaneous tissue in the head pose problems in MRSI. Due to the large voxel size typical in MRSI experiments, ringing artifacts from lipid signals become more prominent and contaminate spectra in brain tissue. This is despite the spatial separation of subcutaneous and brain tissue. This thesis first explores the combination of a 2D MRS method, _Constant Time Point REsolved SpectroScopy (CT-PRESS) with fast spiral encoding in order to achieve feasible scan times for human in-vivo scanning. Human trials were done on a 3.OT scanner and with a 32-channel receive coil array. A lipid contamination minimization algorithm was incorporated for the reduction of lipid artifacts in brain metabolite spectra. This method was applied to the detection of cortical metabolites in the brain and results showed that peaks of metabolites, glutamate, glutamine and N-acetyl-aspartate were recovered after successful lipid suppression. The second task of this thesis was to investigate under-sampling in the indirect time dimension of CT-PRESS and its associated reconstruction with Multi-Task Bayesian Compressed Sensing, which incorporated fully-sampled simulated spectral data as prior information for regularization. It was observed that MT Bayesian CS gave good reconstructions despite simulated incomplete prior knowledge of spectral parameters.
by Trina Kok.
Ph.D.
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Arango, Nicolas(Nicolas S. ). "Sequence-phase optimal (SPO) [d̳e̳l̳t̳a̳]B₀ field control for lipid suppression and homogeneity for brain magnetic resonance spectroscopic imaging." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/128411.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, February, 2020Cataloged from PDF version of thesis. [d̳e̳l̳t̳a̳] in title on title page appears as upper case Greek letter.
Includes bibliographical references (pages 33-35).
This work develops sequence-phase optimal (SPO) [delta]B₀ shimming methods to reduce lipid contamination and improve brain metabolite spectra in proton spectroscopic imaging. A rapidly reconfigurable 32-channel, local-multi-coil-shim-array is used to enhance lipid suppression and narrow metabolite linewidth in magnetic resonance spectroscopic imaging (MRSI) of the brain. The array is optimally reconfigured dynamically during each MRSI repetition period, first during the lipid-suppression phase, by widening the spectral gap between spatially separate lipid and metabolite regions, and then to narrow metabolite linewidth during readout, by brain-only [delta]B₀ homogenization. This sequence-phase-optimal (SPO) shimming approach is demonstrated on four volunteer subjects using a commercial 3T MRI outfitted with a 32-channel integrated RF receive and local multi-coil shim array. This proposed sequence-phase-optimal shimming significantly improves brain-metabolite MRSI in vivo, as measured by lipid suppression, brain metabolite chemical shift, and line widths. The time required to compute patient specific SPO shims negligibly impacted scan time. Sequence-phase-optimal shimming reduced lipid energy in the brain volume across four subjects by 88%, improved NAA FWHM by 23%, and dramatically reduced lipid ringing artifacts in quantified NAA and Glutamate metabolites, without increasing scan time or SAR.
by Nicolas Arango.
S.M.
S.M. Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science
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Gudmundson, Erik. "Signal Processing for Spectroscopic Applications." Doctoral thesis, Uppsala universitet, Avdelningen för systemteknik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-120194.
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Spectroscopic techniques allow for studies of materials and organisms on the atomic and molecular level. Examples of such techniques are nuclear magnetic resonance (NMR) spectroscopy—one of the principal techniques to obtain physical, chemical, electronic and structural information about molecules—and magnetic resonance imaging (MRI)—an important medical imaging technique for, e.g., visualization of the internal structure of the human body. The less well-known spectroscopic technique of nuclear quadrupole resonance (NQR) is related to NMR and MRI but with the difference that no external magnetic field is needed. NQR has found applications in, e.g., detection of explosives and narcotics. The first part of this thesis is focused on detection and identification of solid and liquid explosives using both NQR and NMR data. Methods allowing for uncertainties in the assumed signal amplitudes are proposed, as well as methods for estimation of model parameters that allow for non-uniform sampling of the data. The second part treats two medical applications. Firstly, new, fast methods for parameter estimation in MRI data are presented. MRI can be used for, e.g., the diagnosis of anomalies in the skin or in the brain. The presented methods allow for a significant decrease in computational complexity without loss in performance. Secondly, the estimation of blood flow velo-city using medical ultrasound scanners is addressed. Information about anomalies in the blood flow dynamics is an important tool for the diagnosis of, for example, stenosis and atherosclerosis. The presented methods make no assumption on the sampling schemes, allowing for duplex mode transmissions where B-mode images are interleaved with the Doppler emissions.
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Ross, Amy Psychiatry Faculty of Medicine UNSW. "Longitudinal study of cognitive and functional brain changes in ageing and cerebrovascular disease, using proton magnetic resonance spectroscopy." Awarded by:University of New South Wales. School of Psychiatry, 2005. http://handle.unsw.edu.au/1959.4/27329.
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The neurophysiological basis of cognition changes with age is relatively unexplained, with most studies reporting weak relationships between cognition and measures of brain function, such as event related potentials, brain size and cerebral blood flow. Proton magnetic resonance spectroscopy (1H-MRS) is an in vivo method used to detect metabolites within the brain that are relevant to certain brain processes. Recent studies have shown that these metabolites, in particular N-acetyl aspartate (NAA), which is associated with neuronal viability, correlate with performance on neuropsychological tests or other measures of cognitive function in patients with a variety of cognitive disorders associated with ageing and in normal ageing subjects. We have studied the relationship between metabolites and cognitive function in elderly patients 3 months and 3 years after a stroke or transient ischemic attack (TIA) and in an ageing comparison group. Metabolites were no different between stroke/TIA patients and elderly controls, however, there were significant metabolite differences between stroke/TIA patients with cognitive impairment (Vascular Cognitive Impairment and Vascular Dementia) and those without. Frontal measures of NAA and NAA/Cr predicted cognitive decline over 12 months and 3 years in stroke/TIA patients and elderly controls, and these measures were superior predictors than structural MRI measures. Longitudinal stability of metabolites in ageing over 3 years was associated with stability of cognitive function. The results indicate that 1H-MRS is a useful tool in differentiating stroke/TIA patients with and without cognitive impairment, with possibly superior predictive ability than structural MRI for assessing future cognitive decline. The changes in 1H-MRS that occur with ageing and cognitive decline have implications for the neurophysiological mechanisms and processes that are occurring in the brain, as well as application to clinical diagnosis, the early detection of pathology and the examination of longitudinal change.
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Labadie, Christian. "Gradient-echo pulse sequence development for phase sensitive magnetic resonance imaging : application to the detection of metabolites and myelin water in human brain white matter." Thesis, Lyon 1, 2013. http://www.theses.fr/2013LYO10134.
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Deux méthodes d'imagerie par résonance magnétique sont proposées pour analyser in vivo le tissu cérébral de la matière blanche. La première méthode permet l'acquisition ultra-rapide de cartes des métabolites cérébraux par une lecture de l'espace réciproque répétée à des intervalles de quelques millisecondes à l'aide d'une nouvelle trajectoire excentrée, combinée à un gradient de retour. Une procédure de correction de phase, pour prévenir la formation d'artéfacts de repliement dans l'image et le spectre, est introduite sur la base de paramètres déterminés à partir du signal des protons de l'eau. Une acquisition des cartes métaboliques tridimensionnelles de la créatine, de la choline, du N-acétylaspartate, du glutamate et du myo-inositol ont été déterminées de manière fiable dans la substance blanche humaine à 3 Tesla avec une matrice de taille 32 × 32 × 16 et une résolution isotropique de 7 mm. La deuxième méthode permet l'acquisition d'un train de 32 images échantillonnées géométriquement le long d'une courbe de recroissance, en employant une série d'échos de gradient excités par un angle de bascule de 5° pour éviter des effets de saturation. Après transformée inverse de Laplace utilisant une régularisation spatiale, on obtient une distribution continue des temps de relaxation spin-réseau, T1. Dans la région de T1 entre 100 ms et 230 ms, on distingue un pic attribué à l'eau hydratant les membranes de la myéline. La fraction apparente de cette composante de l'eau de myéline augmente en fonction de l'intensité du champ magnétique, de 8,3 % à 3 Tesla, à 11,3 % à 4 Tesla, pour atteindre 15,0 % à 7 TeslaTwo magnetic resonance imaging methods are proposed for the in vivo investigation of human brain white matter tissue. The first method allows the ultra-fast acquisition of maps of brain metabolites by repeating the sampling of k-space at intervals of a few milliseconds, with a center-out trajectory combined with flyback gradients. A phase-correction procedure is introduced to prevent the formation of aliasing artifacts in the image and in the spectrum, on the basis of parameters determined from the signal of the ubiquitous water protons. An acquisition of threedimensional metabolite maps of creatine, choline, N-acetylaspartate, glutamate, and myo-inositol were determined reliably in human brain white matter at 3 Tesla with a 32 × 32 × 16 matrix and a 7-mm isotropic resolution. The second method enables the acquisition of a train of 32 images geometrically sampled along an inversion-recovery curve, using a series of gradient echoes excited by a low 5° flip angle to avoid saturation effects. After inverse Laplace transform, using a spatial regularization, a continuous distribution of the spin-lattice relaxation times, T1, is obtained. In the region of T1 between 100 ms and 230 ms, a small component is attributed to water hydrating myelin membranes. The apparent fraction of this myelin water component increases with the strength of the magnetic field, from 8.3% at 3 Tesla, to 11.3% at 4 Tesla, and 15.0% at 7 Tesla
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Chiu, Pui-wai, and 趙沛慧. "¹H and ³¹P brain magnetic resonance spectroscopy in aging." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2011. http://hub.hku.hk/bib/B47170505.
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Magnetic Resonance Spectroscopy (MRS) was used to study the relationship between brain regional concentrations of metabolites and normal aging in Chinese. Our goal in this study is to create a database of normal aging and hence enhance further understanding on the degenerative process leading to dementia and related neurodegenerative diseases.
Thirty cognitively normal healthy volunteers of age 22-82 years were recruited and the bias on gender effect in data sampling was minimized by recruiting 15 females and 15 males. In the first part of the study, 1H MRS was obtained using single-voxel-spectroscopy (SVS). Offline software java-based version of Magnetic Resonance User Interface (jMRUI) was employed for data analysis. Cerebrospinal fluid was normalized using software voxel based morphormetry (VBM). Brain morphometry data was also analyzed. Brain metabolites choline (Cho), creatine (Cr) and N-acetyl aspartate (NAA) were quantified using internal water as reference. It was found that brain metabolite concentrations of Cr, Cho and NAA increase significantly with age. Gender effect on metabolite concentrations were also discovered, being higher in the female group. For brain morphometry, white matter and grey matter volumes and fractions all reveal a siginificant negative correlation with age, whereas CSF volume and fraction show a significant positive correlation with age. Gender effect was found on grey matter, white matter and intracranial volume, being higher in the male group.
In the second part of the study, 31P SVS MRS was performed on the same population of volunteers. jMRUI was also employed for data analysis. Metabolic ratios were obtained. Similar to the 1H MRS study, apart from creating a database in studying normal aging, an additional aim of this 31P MRS study is to correlate with 1H MRS and assist in interpreting the corresponding metabolic activity. Brain metabolite concentrations were found to increase significantly with age. The increase of PCr (phosphocreatine)/Ptot (total phosphorus content) in posterior cingulate suggests lower metabolic activity throughout the course of aging. The strong evidence of PDE (phosphodiester) increase with age in left hippocampus proposes the fact that phospholipid membrane breakdown will be enhanced by aging.
In conclusion, MRS can act as a non-invasive tool to study aging at molecular level. Metabolite levels are significant means to investigate the metabolic change in the human brain during the process of aging as the variations in metabolite levels are believed to be footprints of biochemical changes.published_or_final_version
Diagnostic Radiology
Master
Master of Philosophy
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Lebel, Cynthia. "Optical Brain Imaging of Motor Cortex to Decode Movement Direction using Cross-Correlation Analysis." Thesis, University of North Texas, 2019. https://digital.library.unt.edu/ark:/67531/metadc1609111/.
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The goal of this study is to determine the intentional movement direction based on the neural signals recorded from the motor cortex using optical brain imaging techniques. Towards this goal, we developed a cross-correlation analysis technique to determine the movement direction from the hemodynamic signals recorded from the motor cortex. Healthy human subjects were asked to perform a two-dimensional hand movement in two orthogonal directions while the hemodynamic signals were recorded from the motor cortex simultaneously with the movements. The movement directions were correlated with the hemodynamic signals to establish the cross-correlation patterns of firings among these neurons. Based on the specific cross-correlation patterns with respect to the different movement directions, we can distinguish the different intentional movement directions between front-back and right-left movements. This is based on the hypothesis that different movement directions can be determined by different cooperative firings among various groups of neurons. By identifying the different correlation patterns of brain activities with each group of neurons for each movement, we can decode the specific movement direction based on the hemodynamic signals. By developing such a computational method to decode movement direction, it can be used to control the direction of a wheelchair for paralyzed patients based on the changes in hemodynamic signals recorded using non-invasive optical imaging techniques.
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Hall, Michael A. "Temporal Mapping and Connectivity using NIRS for Language Related Tasks." FIU Digital Commons, 2012. http://digitalcommons.fiu.edu/etd/560.
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Near infrared spectroscopy (NIRS) is an emerging neuroimaging modality with high temporal and good spatial resolution. In this thesis, NIRS was applied to understand functionality of the fronto-temporal cortex in response to language-related tasks. A 32-channel NIRS system (Imagent ISS Inc.) was used to perform experimental studies on 15 right-handed normal adults. Block-design based Word Expression and Word Reception paradigms were independently presented to participants. Activation, functional connectivity and cortical lateralization analyses were performed. From word expression studies, results showed left anterior region (encompassing Broca) is majorly involved over right homologue and posterior regions. From the word reception studies, results showed that right posterior region (encompassing right homologue of Wernicke) is highly involved in language reception, with right anterior region (encompassing right homologue of Broca) also involved. The current study has potential future applications in surgical evaluation of language regions in populations with neurological disorders such as epilepsy, and schizophrenia.
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Rothmeier, Greggory H. "Brain tissue temperature dynamics during functional activity and possibilities for optical measurement techniques." Digital Archive @ GSU, 2012. http://digitalarchive.gsu.edu/phy_astr_theses/14.
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Regional tissue temperature dynamics in the brain are determined by the balance of the metabolic heat production rate and heat exchange with blood flowing through capillaries embedded in the brain tissue, the surrounding tissues and the environment. Local changes in blood flow and metabolism during functional activity can upset this balance and induce transient temperature changes. Invasive experimental studies in animal models have estab- lished that the brain temperature changes during functional activity are observable and a definitive relationship exists between temperature and brain activity. We present a theoreti- cal framework that links tissue temperature dynamics with hemodynamic activity allowing us to non-invasively estimate brain temperature changes from experimentally measured blood- oxygen level dependent (BOLD) signals. With this unified approach, we are able to pinpoint the mechanisms for hemodynamic activity-related temperature increases and decreases. In addition to these results, the potential uses and limitations of optical measurements are dis- cussed.
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Oeltzschner, Georg [Verfasser], Alfons [Akademischer Betreuer] Schnitzler, and Thomas [Akademischer Betreuer] Heinzel. "Magnetic resonance spectroscopy and quantitative brain water imaging in patients with hepatic encephalopathy / Georg Oeltzschner. Gutachter: Alfons Schnitzler ; Thomas Heinzel." Düsseldorf : Universitäts- und Landesbibliothek der Heinrich-Heine-Universität Düsseldorf, 2016. http://d-nb.info/1081214538/34.
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Storrs, Judd M. "Automatic Real-time Targeting of Single-Voxel Magnetic Resonance Spectroscopy." University of Cincinnati / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1282576722.
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Myllylä, T. (Teemu). "Multimodal biomedical measurement methods to study brain functions simultaneously with functional magnetic resonance imaging." Doctoral thesis, Oulun yliopisto, 2014. http://urn.fi/urn:isbn:9789526205076.
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Abstract Multimodal measurements are increasingly being employed in the study of human physiology. Brain studies in particular can draw advantage of simultaneous measurements using different modalities to analyse correlations, mechanisms and relationships of physiological signals and their dynamics in relation to brain functions. Moreover, multimodal measurements help to identify components of physiological dynamics generated specifically by the brain. This thesis summarizes the study, design and development of non-invasive medical instruments that can be utilized in conjunction with magnetic resonance imaging (MRI). A key challenge in the development of measurement methods is posed by the extraordinary requirements that the MRI environment poses - all materials need to be MR-compatible and the selected instruments and devices must not be affected by the strong magnetic field generated by the MRI scanner nor the MRI by the instruments placed within its scanning volume. The presented methods allow simultaneous continuous measurement of heart rate (HR) and metabolism from the brain cortex as well as pulse wave velocity (PWV) and blood pressure measurements in synchrony with electroencephalography (EEG) and MRI. Furthermore, the thesis explored the reliability and accuracy of the responses gathered by the developed instruments and, using new experimental methods, estimated the propagation of near-infrared light in the human brain. The goal of the novel multimodal measurement environment is to provide more extensive tools for medical researchers, neurologists in particular, to acquire accurate information on the function of the brain and the human body. Measurements have been performed on more than 70 persons using the presented multimodal setup to study such factors as the correlation between blood oxygen level-dependent (BOLD) data and low-frequency oscillations (LFOs) during the resting stateTiivistelmä Multimodaalisia kuvantamismenetelmiä käytetään enenevässä määrin ihmisen fysiologian ja elintoimintojen tutkimisessa. Erityisesti aivotutkimuksessa samanaikaisesti useammalla modaliteetilla mittaaminen mahdollistaa erilaisten fysiologisten mekanismien ja niiden korrelaatioiden tutkimisen kehon ja aivotoimintojen välillä. Lisäksi multimodaaliset mittaukset auttavat yksilöimään fysiologiset komponentit toisistaan ja identifioimaan aivojen tuottamia fysiologisia signaaleja. Tämä väitöskirja kokoaa tutkimustyön sekä laite- ja instrumentointisuunnittelun ja sen kehittämistyön ei-invasiivisesti toteutettujen lääketieteen mittausmenetelmien käyttämiseksi magneettikuvauksen aikana. Erityishaasteena työssä on ollut magneettikuvausympäristö, joka asettaa erityisvaatimuksia mm. mittalaitteissa käytettäville materiaaleille sekä laitteiden häiriönsiedolle magneettikuvauslaitteen aiheuttaman voimakkaan magneettikentän takia. Kehitettävät mittausmenetelmät eivät myöskään saa aiheuttaa häiriöitä magneettikuvauslaitteen tuottamalle kuvainformaatiolle. Väitöskirjassa esitettävät mittausmenetelmät tekevät mahdolliseksi mitata magneettikuvausympäristössä ihmisen sydämen sykettä, veren virtauksen kulkunopeutta ja verenpaineen vaihteluja sekä aivokuoren metaboliaa - kaikki synkronissa aivosähkökäyrän mittaamisen ja magneettikuvantamisen kanssa. Lisäksi väitöskirjassa tutkitaan kehitettyjen mittausmenetelmien antamaa mittaustarkkuutta sekä arvioidaan lähi-infrapunavalon etenemistä ihmisen aivoissa uudenlaisella menetelmällä. Kehitetyllä multimodaalisella mittausympäristöllä on tavoitteena antaa lääketieteen alan tutkijoille, erityisesti neurologeille, käyttöön mittausmenetelmiä, joiden avulla voidaan tutkia ihmisen aivojen ja kehon välisiä toimintoja aiempaa kattavammin. Laitekokonaisuudella on tutkittu jo yli 70:tä henkilöä. Näissä mittauksissa on tutkittu mm. veren happitasojen hitaita vaihteluja ihmisen aivojen ollessa lepotilassa, ns. resting state -tilassa
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Frangou, Polytimi. "Inhibitory mechanisms for visual learning in the human brain." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/280767.
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Identifying targets in cluttered scenes is critical for our interactions in complex environments. Our visual system is challenged to both detect elusive targets that we may want to avoid or chase and discriminate between targets that are highly similar. These tasks require our visual system to become an expert at detecting distinctive features that help us differentiate between indistinguishable targets. As the human brain is trained on this type of visual tasks, we observe changes in its function that correspond to improved performance. We use functional brain imaging, to measure learning-dependent modulations of brain activation and investigate the processes that mediate functional brain plasticity. I propose that dissociable brain mechanisms are engaged when detecting targets in clutter vs. discriminating between highly similar targets: for the former, background clutter needs to be suppressed for the target to be recognised, whereas for the latter, neurons are tuned to respond to fine differences. Although GABAergic inhibition is known to suppress redundant neuronal populations and tune neuronal representations, its role in visual learning remains largely unexplored. Here, I propose that GABAergic inhibition plays an important role in visual plasticity through training on these tasks. The purpose of my PhD is to investigate the inhibitory mechanisms that mediate visual perceptual learning; in particular, learning to detect patterns in visual clutter and discriminate between highly similar patterns. I show that BOLD signals as measured by functional Magnetic Resonance Imaging (fMRI) do not differentiate between the two proposed mechanisms. In contrast, Magnetic Resonance Spectroscopy (MRS) provides strong evidence for the distinct involvement of GABAergic inhibition in visual plasticity. Further, my findings show GABA changes during the time-course of learning providing evidence for a distinct role of GABA in learning-dependent plasticity across different brain regions involved in visual learning. Finally, I test the causal link between inhibitory contributions and visual plasticity using a brain stimulation intervention that perturbs the excitation-inhibition balance in the visual cortex and facilitates learning.
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Rutter, Allison. "An NMR study of human brain tumours: Phosphorus chemical shift imaging in vivo and high resolution proton spectroscopy of biopsy samples." Thesis, University of Ottawa (Canada), 1992. http://hdl.handle.net/10393/7681.
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Human brain tumours have been investigated using proton and phosphorus nuclear magnetic resonance (NMR). The localization technique, chemical shift imaging has been used to obtain phosphorus spectra of tumours in vivo. High resolution proton spectroscopy has been performed on biopsy samples and extracts of human brain tumours. To obtain the localized phosphorus spectra, one dimensional chemical shift imaging with a surface coil was adapted to a 1.5 T Siemens Magnetom imager. The ratios of areas, PDE/ATP and PME/ATP were found to be higher in glioblastomas and astrocytomas than in normal brain. Pi/ATP and PCr/ATP were also high in astrocytomas. The pH of brain tumours ranged from alkaline to neutral, with meningiomas consistently having alkaline pH. A three dimensional localization sequence was written and tested on the Magnetom and used to obtain phosphorus spectra from the brains of normal volunteers. One dimensional $\sp1$H spectra, COSY spectra and T$\sb2$ data were obtained from ex vivo biopsy samples. A parameter, P, was defined as the ratio of the area between 3.4 and 3.1. ppm over the area between 1.5 ppm and 1.1 ppm. The parameter distinguished glioblastomas from astrocytomas and normal brain. This area parameter, P, also appeared to be indicative of malignant potential or biological aggressiveness. Crosspeaks in the ex vivo proton COSY spectra of brain specimens could be used to classify glioblastomas, astrocytomas, metastases to the brain, meningiomas and normal brain in agreement with histopathological diagnosis. The T$\sb2$ values at 1.3 ppm were fitted to a two exponential equation. The longer component could be used to separate clearly glioblastomas from normal brain, normal brain having a much longer long T$\sb2$ component. Astrocytomas formed a continuum of values between glioblastomas and normal brain, with the grade of the astrocytoma roughly correlating with the value of the long T$\sb2$ component. High resolution $\sp1$H spectroscopy of perchloric acid extracts of biopsy samples was performed. The extracts confirmed that lactate, acetate, creatine and choline derivatives, NAA, glutamate, glutamine, alanine, valine and leucine were present in the samples. Comparisons of extract and ex vivo spectra indicated that the 1.3 ppm peak in the ex vivo spectra is predominantly due to the methylene moiety of lipids.
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Corwin, Frank. "Characterization of a Blast Wave Device and Blast Wave Induced Traumatic Brain Injury in a Rat Model by Magnetic Resonance Imaging and Spectroscopy." VCU Scholars Compass, 2011. http://scholarscompass.vcu.edu/etd/2403.
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Blast wave induced traumatic brain injury (bTBI) is a modality of injury that has come into prominence at the current time due to the large number of military and civilian personnel who have experienced the localized shock wave produced by explosive devices. The shock wave will travel concentrically outward from the explosive center, being absorbed and transmitted thru soft objects, such as tissue, and reflecting off stationary obstructions. Transmission and absorption in tissues can result in a number of physiological measureable injuries, the most common of which being what is frequently called “blast lung”. Blast lung involves the spalling effect at air-tissue interfaces. Another documented effect involves the asynchronous motion of tissue, particularly in the cranium, as the shock wave passes by. This predominately manifests itself in what is believed to be diffuse axonal injury and initiation of secondary injury mechanism. This study is designed to explore the relationship between shock waves and bTBI. A blast device was constructed for generating a free field shock wave through the high pressure rupture of a polycarbonate membrane. Air pressure in a small chamber is increased to a value several orders of magnitude greater than ambient air pressure and is held in place with the polycarbonate member. At the rupture of this membrane a shock wave is created. Measurements of this blast event, carried out with a piezoelectric pressure transducer, have shown that this shock wave is reproducible for the different membrane materials tested and is symmetrical with respect to the central axis of the high pressure chamber and exit nozzle. Having characterized the shock wave properties in the blast field, a location was chosen at which maximum shock wave pressure could be applied to the cranium for inducing bTBI. Experiments involving blast wave exposure were performed on two separate groups of animals in an attempt at establishing injury. One group was placed at a fixed distance directly below the blast nozzle, thereby experiencing both the shock wave and the associated air blast from the residual air in the chamber, and one placed at a defined distance off-axis to avoid the air blast, yet receiving two sequential blast exposures. All animal studies were approved by the VCU Institutional Animal Care and Use Committee. The degree of injury was then assessed with the use of magnetic resonance imaging (MRI) and spectroscopy (MRS). Image Data was acquired on a 2.4 Tesla magnet for assessing changes in either the total percent water concentration or the apparent diffusion coefficients (ADC) of selected regions of interest in the brain of rats. Localized proton spectroscopic data was acquired from a voxel placed centrally in the brain. The baseline values of these parameters were established before the induction of bTBI. After the blast exposure, the animals were followed up with MRI and MRS at defined intervals over a period of one week. The first group of animals received blast exposure directly underneath the blast device nozzle and the MR data does suggest changes in some of the measureable parameters from baseline following blast exposure. This blast wave data though is confounded with additional and undesirable characteristics of the blast wave. The second group of animals that received a pure shock wave blast exposure revealed no remarkable changes in the MR data pre- to post- blast exposure. The percent water concentration, ADC and spectroscopic parameters were for statistical purposes identical before and after the blast. The resolution of this negative result will require reconsideration of the free field blast exposure concept.
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Morken, Tora Sund. "Brain development and metabolism after hypoxia-ischemia and varying oxygen levels in the neonatal rat studied with 13C-MR spectroscopy and multimodal MR imaging." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for laboratoriemedisin, barne- og kvinnesykdommer, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-23712.
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Ojha, Navdeep. "Imaging of tissue injury-repair addressing the significance of oxygen and its derivatives." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1196204993.
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Martel, Dimitri. "Spectroscopie 2D de corrélation quantitative : Méthode de quantification, études expérimentales et applications in vivo." Thesis, Lyon, INSA, 2015. http://www.theses.fr/2015ISAL0004/document.
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En spectroscopie de résonance magnétique (SRM) in vivo, les principales méthodes utilisées permettent la quantification des concentrations de métabolites en utilisant des signaux à une dimension spectrale. Les travaux réalisés dans le cadre de cette thèse portent sur le développement de méthodes de SRM à deux dimensions spectrales (SRM 2D) de corrélation localisée afin d’accroître le pouvoir de résolution spectrale et la précision de la quantification de la SRM in vivo. Le premier axe de cette thèse concerne le développement d’une méthode fondée sur la spectroscopie 2D de corrélation localisée pour l’exploration des métabolites cérébraux. La séquence L-COSY (spectroscopie de corrélation localisée) est implantée sur imageur petit animal et étudiée. Une procédure de quantification dédiée aux signaux de corrélation acquis est développée. Cette dernière opère dans le domaine d’acquisition du signal, et s’appuie sur : 1) une connaissance a priori forte obtenue par simulation de l’effet quantique des séquences sur les spins des composés présents dans le spectre 2) un modèle de pondération lié aux effets de relaxation agissant sur le signal de SRM 2D. 3) une contrainte sur la relaxation liée aux effets d’inhomogénéités supposés toucher tous les spins de la même manière. Les résultats présentés s’attachent à étudier les performances quantitatives de la SRM 2D de corrélation, en comparaison à la SRM 2D dite J-résolue (avec la séquence JPRESS), de manière expérimentale, sur fantômes de métabolites mais aussi à travers la théorie des bornes de Cramér-Rao (CRBs). La quantification des signaux L-COSY, bien que défavorisée par une perte théorique du rapport signal sur bruit par unité de temps, présente des CRBs théoriques relatives du même ordre de grandeurs voire, pour certains métabolites couplés (e.g la glutamine, le GABA) plus petites que celles correspondantes à la spectroscopie J-résolue pour un même temps d’acquisition. Le second axe de cette thèse porte sur l’adaptation la SRM 2D de corrélation pour l’étude in vivo du métabolisme lipidique du foie et des tissus adipeux sous-cutanés sur un modèle de souris obèse à 7T. Cette application inédite montre la faisabilité de la SRM 2D de corrélation à être acquise sur un tel organe mouvant et sa capacité à être quantitative pour l’étude et la caractérisation des triglycérides hépatiques et sous-cutanéesIn in vivo Magnetic Resonance Spectroscopy (MRS), the main methods used allow metabolite concentration quantification using signals having one spectral dimension. This work focuses on the development of in vivo two dimensional correlated MRS in order to increase spectral resolution and quantification precision. The first axis is about the development of a method based on a 2D localized correlation MRS (L-COSY) for brain metabolite exploration. The L-COSY is implemented and studied on a small animal scanner. A dedicated quantification procedure operating in the acquisition domain is described. This latter is based on 1) a strong prior knowledge obtained by quantum mechanically simulate the effect of sequence on metabolite spin systems 2) a model function taking into account the relaxation weighting 3) constraints on the relaxation term linked to the field inhomogeneity effects which are assumed to act the same way on all the spins. Results are given experimentally using metabolites phantoms and through a comparison to other existing 2D MRS method, namely the J-resolved MRS (with the JPRESS sequence) using the Cramer Rao Lower Bounds (CRBs) theory. Although its inherent loss of signal to noise ratio is a disadvantage compared to J-PRESS, L-COSY quantification shows theoretically competitive relative CRBs, and even smaller CRBs for some coupled metabolites (e.g Glutamine or GABA), for an acquisition time similar to JPRESS. Second axis is about the adaptation of the 2D correlation MRS for the in vivo lipid metabolism study in the liver and subcutaneous adipose tissues of obese mice at 7T. This application shows the feasibility of 2D correlated MRS to be acquired on a moving organ and its quantitative relevance for triglyceride quantification and characterization in fatty liver and subcutaneous tissue
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Dahlqvist, Leinhard Olof. "Quantitative Magnetic Resonance in Diffuse Neurological and Liver Disease." Doctoral thesis, Linköping : Department of Medical and Health Sciences, Linköping University, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-54728.
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Schmitz, Birte [Verfasser], Xiaoqi [Akademischer Betreuer] Ding, and Karin [Akademischer Betreuer] Weißenborn. "Investigation of metabolic and microstructural alterations in human brain under physiological and pathological conditions by using magnetic resonance imaging and 1H and 31P magnetic resonance spectroscopy / Birte Schmitz ; Akademische Betreuer: Xiaoqi Ding, Karin Weißenborn ; Institut für Diagnostische und Interventionelle Neuroradiologie." Hannover : Bibliothek der Medizinischen Hochschule Hannover, 2020. http://d-nb.info/1225413656/34.
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Fellah, Slim. "Exploration par IRM multimodale des tumeurs cérébrales de l'enfant et de l'adulte. : Lésions épileptogènes, tumeurs oligodendrogliales et glioblastome." Thesis, Aix-Marseille, 2012. http://www.theses.fr/2012AIXM5035.
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L'IRM conventionnelle est considérée comme l'outil non invasif de référence pour le diagnostic, le bilan pré-thérapeutique et le suivi post-thérapeutique des tumeurs cérébrales de l'enfant et de l'adulte. Cependant, en raison de son manque de spécificité aussi bien pour certains diagnostics différentiels que pour l'évaluation de la réponse radiologique, différentes modalités d'IRM sont aujourd'hui ajoutées à l'examen conventionnel dans le but d'affiner l'exploration de ces tumeurs. L'utilisation d'une modalité unique n'est malgré tout pas suffisante pour établir une évaluation diagnostique ou pronostique optimale des tumeurs cérébrales. C'est pourquoi nous nous sommes intéressés à la combinaison de données issues des différentes modalités d'IRM dans le but d'obtenir une meilleure caractérisation, en termes de différenciation et d'évolutivité de ces néoplasmes. Dans ce contexte, nous avons investigué par IRM multimodale 1) les tumeurs épileptogènes de l'enfant, pour lesquelles il est crucial de déterminer le diagnostic préopératoire afin d'aider à la prise en charge chirurgicale ; 2) les tumeurs oligodendrogliales de l'adulte, difficilement distinguables et dont les décisions thérapeutiques reposent sur la détermination du grade et du profil moléculaire ; et enfin 3) la réponse des glioblastomes aux traitements anti-angiogéniquesConventional MRI is considered as the gold standard method for the non-invasive diagnosis, pretherapeutic assessment and follow-up of brain tumors in adults and in children. However, due to its lack of specificity for both differential diagnosis and evaluation of the response to treatment, several MR modalities are now added to the conventional exam in order to refine the exploration of these tumors. The use of a single modality is however not yet sufficient to establish an accurate diagnosis or prognosis for brain tumors. For this reason, we were interested in the combination of data from different MR modalities in order to obtain a better characterization of these neoplasms. In this context, we used multimodal MRI to investigate 1) pediatric epileptogenic tumors, for which it is crucial to establish a preoperative diagnosis in order to make appropriate surgical and therapeutic decisions; 2) oligodendroglial tumors in adults, hardly distinguishable and which therapeutic decisions are mainly based on the determination of the tumoral grade and molecular profile; and 3) the response of glioblastoma to anti-angiogenic treatments. Through this work, we have shown that the association of different imaging modalities provides a significant contribution to the differential pre-therapeutic diagnosis of epileptogenic brain lesions in children and also of oligodendroglial tumors in adults as well as a support for the early assessment of tumoral response to anti-angiogenic therapies
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Bruhn, Harald. "Untersuchungen physiologischer und pathophysiologischer Stoffwechselzustände und Hirnfunktionen des Menschen mit Hilfe neuer methodischer Entwicklungen zur ortsaufgelösten Magnetresonanz-Spektroskopie und funktionellen Magnetresonanz-Tomografie." Doctoral thesis, Humboldt-Universität zu Berlin, Medizinische Fakultät - Universitätsklinikum Charité, 2001. http://dx.doi.org/10.18452/13769.
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Diese Schrift faßt in zwei Abschnitten eigene Beiträge zur Einführung der lokalisierten Magnetresonanzspektroskopie (MRS) und der funktionellen Magnetresonanztomografie (fMRT) in die diagnostische Medizin zusammen. Im ersten Teil wird beschrieben, wie die biochemischen Metabolite N-Azetylaspartat, Kreatin und Phosphokreatin, cholin-enthaltende Verbindungen und Laktat durch die Einführung der stimulierten Echo-Akquisitionsmethode (STEAM) als Lokalisationstechnik in die diagnostische Magnetresonanzspektroskopie in definierten Hirnregionen gesunder Versuchspersonen nichtinvasiv zugänglich gemacht und erstmals in Form von In-vivo-Konzentrationen quantifiziert werden konnten. Daraufhin wird gezeigt, wie die Weiterentwicklung der robusten STEAM-Technik zu kurzen Echozeiten das Signal-zu-Rauschverhältnis und damit die Messung kleinerer Untersuchungsvolumina erheblich verbesserte. Zudem wurde dadurch die Erkennung und Quantifizierung weiterer Metabolite wie z. B. des myo- und scyllo-Inosits, des Glutamats und Glutamins, des N-Azetylaspartylglutamats und der Glukose ermöglicht. Diese Methode setzte damit zusammen mit der verwendeten linearen Kombinationsmethode (LCModel) zur Konzentrationsbestimmung den spektralen Qualitätsstandard des gesamten letzten Jahrzehnts. Ferner werden die parallelen Pionierarbeiten zu Hirnerkrankungen fokaler und generalisierter Art beleuchtet. Diese Anwendungen der lokalisierten STEAM-Protonenspektroskopie in Einzelvolumentechnik zur Messung umschriebener Prozesse umfassen zerebrale Tumore und Infarkte, Plaques der multiplen Sklerose sowie andere entzündliche und degenerative Läsionen. Auch die lokalisierte STEAM-Phosphorspektroskopie und nichtzerebrale Anwendungen wie die lokalisierte Protonenspektroskopie von Faserbündeln des Skelettmuskels und der Niere bauen weitgehend auf diesem Fortschritt in der Methode auf. Zusätzlich werden Anwendungen bei generalisierten Erkrankungen gestreift, speziell angeborenen Stoffwechselerkrankungen des Kindesalters wie mitochondrialen und lysosomalen Defekten, Stoffwechselentgleisungen bei Diabetes mellitus und Leberzirrhose, psychiatrischen Erkrankungen wie der Alzheimer-Demenz. Die weitere Verbreitung dieser Erkenntnisse in die klinische Diagnostik wird entscheidend von der Beachtung des hier eingeführten Qualitätsmaßstabs und der darauf aufbauenden absoluten Metabolitquantifizierung abhängen. Der zweite Teil dieser Arbeit faßt ausgehend von funktionellen protonenspektroskopischen Untersuchungen des visuellen Kortex bei photischer Aktivierung Fortschritte zusammen, die bei der Entwicklung und Anwendung der suszeptibilitätsempfindlichen MR-Tomografie zur Messung physiologischer Hirnaktivierung mit dem Modell der visuellen Stimulation erzielt wurden. Während die Belastung des Energiestoffwechsels im angeregten striatären Kortex anhand abgesunkener Gewebespiegel von Glukose und angestiegener Laktatkonzentrationen mithilfe der zeitaufgelösten Spektroskopie beobachtet werden konnte, gelang die Demarkierung der Ausdehnung der Hirngewebeaktivierung mithilfe der T2*-gewichteten FLASH-MRT, die begleitende Verminderungen des paramagnetischen Desoxyhämoglobins im funktionell aktiven Gewebe mit Anstiegen der Bildsignalintensität wiedergibt. Schließlich werden Untersuchungen beschrieben, die die Empfindlichkeit dieses endogenen, sauerstoffspiegelabhängigen Suszeptibilitätskontrastes für die Wirkung verschiedener Medikamente bzw. pharmakologischer Stimulantien zeigen, die direkt oder indirekt über bestimmte vaskuläre Rezeptoren wirken. Diese Untersuchungen befördern wiederum ein neues Gebiet der Bildgebung, die pharmakologische MRT.This work has two main parts that summarize pioneering contributions to localized magnetic resonance spectroscopy (MRS), functional magnetic resonance tomography (fMRI), and the introduction of these modalities into diagnostic medicine. First, it is described how biochemical metabolites such as the intracellular pools of N-acetylaspartate, creatine and phosphocreatine, choline-containing compounds, and lactate have been made accessible to noninvasive detection and to the quantification of their respective concentrations in vivo in defined cerebral regions of healthy subjects by utilizing the stimulated echo-acquisition mode (STEAM) localization technique. Then it is shown that further development of the robust STEAM technique to short echo times not only increased the signal-to-noise of the measurement, thereby providing access to smaller volumes-of-interest, but also allowed for the detection and quantification of additional metabolites such as myo- and scyllo-inositol, glutamate, glutamine, N-acetylaspartylglutamate, and glucose. Thus, together with the adoption of the linear combination method (LCModel) for concentration calculation, this method has set the standard for spectroscopic state-of-the-art in the field well over the last decade. Moreover, pioneering achievements have been highlighted with regard to applications in brain diseases of focal and generalized nature. Pertinent applications of localized single-volume STEAM proton spectroscopy to circumscribed processes include cerebral tumors, cerebral infarction, multiple sclerosis plaques, and other inflammatory and degenerative lesions. Also localized STEAM phosphorus spectroscopy and non-cerebral applications including localized proton spectroscopy of skeletal muscle and kidney largely depend on the short-echo time STEAM technique. In addition, applications in generalized disorders have been explored, which include inborn errors of metabolism in childhood, such as mitochondrial and lysosomal defects, metabolic disturbances in diabetes mellitus and liver cirrhosis, and psychiatric diseases such as Alzheimer's dementia. The further utilization of these novel methods in clinical diagnostics will heavily depend on quality measures and the mastering of a true quantification procedure as demonstrated. Second, this work summarizes achievements made in developing and applying both proton MR spectroscopy and susceptibility-sensitized MR imaging to measure physiologic brain activation using visual stimulation as a model. Whereas metabolic stress, brought upon the bioenergetic steady state in the responding striate cortex, was detected by decreased parenchymal glucose and increased lactate using time-resolved spectroscopy, mapping the extent of parenchymal activation was found to be possible by increases of image intensity in T2*-weighted FLASH MRI made sensitive to concomitant decreases of paramagnetic deoxyhemoglobin in the functionally active tissue. Finally, studies are described, which show the sensitivity of this endogenous, susceptibility-sensitive contrast, now generally known as BOLD effect, to various drugs or pharmacologic stimuli acting either directly or indirectly on vascular receptors. These latter studies open up again a new field of imaging, dubbed pharmacologic MRI.
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Perrillat-Mercerot, Angélique. "Modélisation et étude du métabolisme énergétique cérébral. Applications à l'imagerie des gliomes diffus de bas grade." Thesis, Poitiers, 2019. http://www.theses.fr/2019POIT2285/document.
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Tout ce qui vit, naît, se nourrit, se reproduit et meurt. Pour le cerveau, la question se complexifie car à la survie des neurones s'ajoute le coût de l'activité cérébrale. La question de la gestion énergétique pour les neurones est particulière car les cellules de notre cerveau évoluent de manière concertée et non par compétition. On sait avec l'imagerie médicale que l'usine neuronale ne fonctionne pas uniquement grâce au glucose ; elle utilise d'autres apports énergétiques tels que le lactate ou le glutamate pour soutenir sa production. Lorsqu'une tumeur apparaît, elle change le métabolisme énergétique pour survivre et soutenir sa propre croissance. En particulier, les cellules cancéreuses se fournissent en lactate et choisissent leur substrat préféré en fonction de l'oxygène disponible. La modélisation mathématique des substrats énergétiques est un outil de choix pour décrire et prédire de tels flux. Coupler ces modèles à des données issues de l'IRM et de la SRM permet d'améliorer la prise en charge du patient présentant un gliome.Cette thèse propose l'approche de plusieurs dynamiques en substrat dans le cerveau sain et gliomateux en se basant sur des systèmes d'équations : échanges locaux en lactate (EDO, système lent-rapide), échanges globaux en substrats (EDO), cycle glutamate/glutamine (EDR) et échanges en lactate en dimensions supérieures (EDP). Ces modèles sont expliqués, décrits grâce aux mathématiques et permettent l'élaboration de simulations ajustées selon des données patient ou issues de la littérature.L'énergie est nécessaire au maintien de la vie. Mais si votre voisin consomme une partie de vos ressources, pouvez-vous encore espérer survivre ?Everything that lives is born, eats, reproduces and dies. For the brain, the question is more complex because neurons have to survive and to support brain activity. Energy management is also particular because brain cells evolve together with no competition. Thanks to medical imaging, we know that neurons do not consume only glucose. They can use others energetic substrates such as lactate and glutamate as a power source.When a tumor appears, it changes the energetic metabolism to survive and support its own growth. In particular, cancer cells like to consume lactate. They also choose their favorite substrate based on the available oxygen. Modeling of energy substrates is useful to describe and predict energetic kinetics and changes. Mathematical models could get with clinical and medical results to describe, explain or predict low grade glioma dynamics. They can help to characterize and quantify a tumor evolution, then leading to improve their therapeutical management. Exchanges between mathematics and MRI (and MRS) enable to get accurate data and to build suitable mathematical models.This thesis deals with several approaches of substrates dynamics in healthy and gliomatous brains. These researches are based on systems of equations. We model local lactate exchanges (ODE, fast-slow systems), global substrates exchanges (ODE), glutamate/glutamine cycle (RDE) and local lactate exchanges in higher dimensions (PDE). We describe, analyze and give simulations of these models. Simulations are fitted on patient MRI data or literature data. Energy is necessary to live. But if your neighbor consumes a part of your resources, can you still survive ?
Tutto ciò che vive nasce, si nutre, si riproduce e muore. Per il cervello, la questione è più complessa perché i neuroni devono sopravvivere e sostenere l'attività cerebrale. La gestione energetica cerebrale è particolare anche perché le cellule cerebrali evolvono insieme, senza concorrenza. Inoltre, grazie alle immagini mediche, sappiamo che i neuroni non consumano solo del glucosio ma usano altri substrati energetici come il lattato o il glutammato.Quando un tumore si stabilisce, cambia il metabolismo energetico del cervello per sopravvivere e sostenere la propria crescita. In particolare, cellule tumorali consumano del lattato e scelgono il loro substrato preferito basandosi all'ossigeno disponibile.La matematica, e in particolare l'elaborazione di modelli matematici può aiutarci a ottimizzare i dati disponibili, che possono essere, di volta in volta, delle proprietà cellulare o delle lastre MRI o MRS. La modellizzazione dei substrati energetici potrebbe descrivere, spiegare o prevedere le dinamiche energetiche nel cervello.Questa tesi tratta di diversi approcci della dinamica dei substrati nei cervelli sani e gliomatosi. Queste ricerche si basano su sistemi di equazioni. Modellizziamo scambi locali di lattato (ODE, sistemi fast-slow), scambi globali di substrati (ODE), ciclo glutammato/glutammina (RDE) e scambi locali di lattato in dimensioni superiori (PDE). Descriviamo, analizziamo e diamo simulazioni di questi modelli. Le simulazioni sono adeguate su dati MRI paziente o dati di letteratura.Per vivere, l’energia è una necessità. Ma se i Suoi vicini consumassero le Sue risorse, riuscirebbe ancora a sopravvivere ?
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Sapey-Triomphe, Laurie-Anne. "Inférence et apprentissage perceptifs dans l’autisme : une approche comportementale et neurophysiologique." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSE1130/document.
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La perception de notre environnement repose sur les informations sensorielles reçues, mais aussi sur nos a priori. Dans le cadre Bayésien, ces a priori capturent les régularités de notre environnement et sont essentiels pour inférer les causes de nos sensations. Récemment, les théories du cerveau Bayésien ont été appliquées à l'autisme pour tenter d'en expliquer les symptômes. Les troubles du spectre de l'autisme (TSA) sont caractérisés par des difficultés de compréhension des interactions sociales, par des comportements restreints et répétitifs, et par une perception sensorielle atypique.Cette thèse vise à caractériser l'inférence et l'apprentissage perceptifs dans les TSA, en étudiant la sensorialité et la construction d'a priori. Nous avons utilisé des tests comportementaux, des modèles computationnels, des questionnaires, de l'imagerie fonctionnelle et de la spectroscopie par résonnance magnétique chez des adultes avec ou sans TSA. La définition des profils sensoriels de personnes avec des hauts quotients autistiques a été affinée grâce à un questionnaire dont nous avons validé la traduction française. En explorant les stratégies d'apprentissage perceptif, nous avons ensuite montré que les personnes avec TSA étaient moins enclines à spontanément utiliser une mode d'apprentissage permettant de généraliser. L'étude de la construction implicite des a priori a montré que les personnes avec TSA étaient capables d'apprendre un a priori, mais l'ajustaient difficilement suite à un changement de contexte. Enfin, l'étude des corrélats neurophysiologiques de l'inférence perceptive a révélé un réseau cérébral et une neuromodulation différents dans les TSA.L'ensemble de ces résultats met en lumière une perception atypique dans les TSA, marquée par un apprentissage et une pondération anormale des a priori. Une approche Bayésienne des TSA pourrait améliorer leur caractérisation, diagnostics et prises en chargeHow we perceive our environment relies both on sensory information and on our priors or expectations. Within the Baysian framework, these priors capture the underlying statistical regularities of our environment and allow inferring sensation causes. Recently, Bayesian brain theories suggested that autistic symptoms could arise from an atypical weighting of sensory information and priors. Autism spectrum disorders (ASD) is characterized defined by difficulties in social interactions, by restricted and repetitive patterns of behaviors, and by an atypical sensory perception.This thesis aims at characterizing perceptual inference and learning in ASD, and studies sensory sensitivity and prior learning. This was investigated using behavioral tasks, computational models, questionnaires, functional magnetic resonance imaging and magnetic resonance spectroscopy in adults with or without ASD. Sensory profiles in people with high autism spectrum quotients were first refined, using a questionnaire that we validated in French. The study of perceptual learning strategies then revealed that subjects with ASD were less inclined to spontaneously use a learning style enabling generalization. The implicit learning of priors was explored and showed that subjects with ASD were able to build up a prior but had difficulties adjusting it in changing contexts. Finally, the investigation of the neurophysiological correlates and molecular underpinnings of a similar task showed that perceptual decisions biased by priors relied on a distinct neural network in ASD, and was not related to the same modulation by the glutamate/GABA ratio.The overall results shed light on an atypical learning and weighting of priors in ASD, resulting in an abnormal perceptual inference. A Bayesian approach could help characterizing ASD and could contribute to ASD diagnosis and care
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Henninger, Nils. "Inhibiting Axon Degeneration in a Mouse Model of Acute Brain Injury Through Deletion of Sarm1." eScholarship@UMMS, 2017. http://escholarship.umassmed.edu/gsbs_diss/900.
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Traumatic brain injury (TBI) is a leading cause of disability worldwide. Annually, 150 to 200/1,000,000 people become disabled as a result of brain trauma. Axonal degeneration is a critical, early event following TBI of all severities but whether axon degeneration is a driver of TBI remains unclear. Molecular pathways underlying the pathology of TBI have not been defined and there is no efficacious treatment for TBI.
Despite this significant societal impact, surprisingly little is known about the molecular mechanisms that actively drive axon degeneration in any context and particularly following TBI. Although severe brain injury may cause immediate disruption of axons (primary axotomy), it is now recognized that the most frequent form of traumatic axonal injury (TAI) is mediated by a cascade of events that ultimately result in secondary axonal disconnection (secondary axotomy) within hours to days.
Proposed mechanisms include immediate post-traumatic cytoskeletal destabilization as a direct result of mechanical breakage of microtubules, as well as catastrophic local calcium dysregulation resulting in microtubule depolymerization, impaired axonal transport, unmitigated accumulation of cargoes, local axonal swelling, and finally disconnection. The portion of the axon that is distal to the axotomy site remains initially morphologically intact. However, it undergoes sudden rapid fragmentation along its full distal length ~72 h after the original axotomy, a process termed Wallerian degeneration.
Remarkably, mice mutant for the Wallerian degeneration slow (Wlds) protein exhibit ~tenfold (for 2–3 weeks) suppressed Wallerian degeneration. Yet, pharmacological replication of the Wlds mechanism has proven difficult. Further, no one has studied whether Wlds protects from TAI. Lastly, owing to Wlds presumed gain-of-function and its absence in wild-type animals, direct evidence in support of a putative endogenous axon death signaling pathway is lacking, which is critical to identify original treatment targets and the development of viable therapeutic approaches.
Novel insight into the pathophysiology of Wallerian degeneration was gained by the discovery that mutant Drosophila flies lacking dSarm (sterile a/Armadillo/Toll-Interleukin receptor homology domain protein) cell-autonomously recapitulated the Wlds phenotype. The pro-degenerative function of the dSarm gene (and its mouse homolog Sarm1) is widespread in mammals as shown by in vitro protection of superior cervical ganglion, dorsal root ganglion, and cortical neuron axons, as well as remarkable in-vivo long-term survival (>2 weeks) of transected sciatic mouse Sarm1 null axons. Although the molecular mechanism of function remains to be clarified, its discovery provides direct evidence that Sarm1 is the first endogenous gene required for Wallerian degeneration, driving a highly conserved genetic axon death program.
The central goals of this thesis were to determine (1) whether post-traumatic axonal integrity is preserved in mice lacking Sarm1, and (2) whether loss of Sarm1 is associated with improved functional outcome after TBI. I show that mice lacking the mouse Toll receptor adaptor Sarm1 gene demonstrate multiple improved TBI-associated phenotypes after injury in a closed-head mild TBI model. Sarm1-/- mice developed fewer beta amyloid precursor protein (βAPP) aggregates in axons of the corpus callosum after TBI as compared to Sarm1+/+ mice. Furthermore, mice lacking Sarm1 had reduced plasma concentrations of the phosphorylated axonal neurofilament subunit H, indicating that axonal integrity is maintained after TBI. Strikingly, whereas wild type mice exhibited a number of behavioral deficits after TBI, I observed a strong, early preservation of neurological function in Sarm1-/- animals. Finally, using in vivo proton magnetic resonance spectroscopy, I found tissue signatures consistent with substantially preserved neuronal energy metabolism in Sarm1-/- mice compared to controls immediately following TBI. My results indicate that the Sarm1-mediated prodegenerative pathway promotes pathogenesis in TBI and suggest that anti-Sarm1 therapeutics are a viable approach for preserving neurological function after TBI.
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Wegrzyk, Jennifer. "Wide-pulse, high-frequency electrical stimulation" in humans : Combined investigations of neural and muscular function using electrophysiological and nuclear magnetic resonance techniques." Thesis, Aix-Marseille, 2014. http://www.theses.fr/2014AIXM4080.
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L'ectrostimulation dite conventionnelle (CONV) est délivrée par des impulsions électriques de basse fréquence (≤ 50 Hz), de courte durée (< 400 μs) et de haute intensité. Ce type d'ESNM permet ainsi d'évoquer une contraction musculaire grâce à l'activation directe des axones moteurs et est associé à une fatigue musculaire exagérée par rapport aux contractions volontaires (VOL). Au contraire, lors de l'utilisation d'impulsions de longues durées (1 ms), de hautes fréquences (≥ 80 Hz) et de faibles intensités (i.e. protocole « Wide-Pulse, High-Frequency » (WPHF)), une partie de la force musculaire évoquée aurait pour origine des mécanismes centraux. En effet, une augmentation de la force produite en réponse à WPHF a été rapportée alors que l'intensité de stimulation était constante. Cette « extra force » (EF) refléterait le recrutement par voie réflexe des motoneurones spinaux. L'objectif de ce travail de thèse était de mieux appréhender les mécanismes neurophysiologiques à l'origine de l'EF et d'évaluer les conséquences métaboliques et corticales du protocole WPHF (1 ms - 100 Hz) par rapport à des protocoles d'exercices VOL et de type CONV (50 μs - 25 Hz). Les réponses musculaires des fléchisseurs plantaires et les réponses cérébrales ont été évalué par résonance magnétique nucléaire (la spectroscopie par résonance magnétique du phosphore 31 du muscle et l'imagerie par résonance magnétique fonctionnelle du cerveau) et électrophysiologie (EMG). Ces résultats constituent une première étape importante vers une meilleure prise en charge des pathologies liées à des atteintes du neuromusculaireConventional neuromuscular electrical stimulation (CONV) is delivered via surface electrodes at short pulse duration (< 400 μs), low frequencies (≤ 50 Hz) and high current intensities. The motor unit recruitment pattern of CONV, however, is different from the pattern of voluntary contractions (VOL) and leads to a hastened onset of muscle fatigue. The use of wide-pulses (1ms), high frequencies (100 Hz) (WPHF) and low current intensities might approach the natural activation pattern of VOL by enhancing the neural contribution to force production. Previous studies investigating WPHF reported progressive and unexpected force increments ("Extra Forces") despite a constant stimulation intensity which might reflect the more pronounced activation of sensory pathways within the central nervous system. The objective of this thesis was to investigate this "Extra Force" (EF) phenomenon and to evaluate the efficiency of WPHF (1 ms pulse duration at 100 Hz) in terms of metabolic demand and neural contribution to force production in comparison to CONV NMES (0.05 ms pulse duration at 25 Hz) and VOL. Our experiments comprised electrophysiological (EMG) and nuclear magnetic resonance techniques (31P spectroscopy of the muscle, functional imaging of the brain). The findings should be considered in future studies investigating the potential of NMES in a clinical context as a treatment for neuromuscular pathologies
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Bojan, Jelača. "Dijagnostički značaj i pouzdanost stereotaksične biopsije u tretmanu pacijenata sa tumorima mozga." Phd thesis, Univerzitet u Novom Sadu, Medicinski fakultet u Novom Sadu, 2018. https://www.cris.uns.ac.rs/record.jsf?recordId=107296&source=NDLTD&language=en.
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Uvod: Implementacija brojnih neuroradioloških modaliteta je značajno uticala na način i efikasnost sprovođenja dijagnostike tumora mozga. Na osnovu neinvazivno dobijenih podataka može se postaviti diferencijalna dijagnoza, ali do sada nije potvrđena nijedna neuroradiološka metoda koja može samostalno i konačno da postavi definitivnu patohistološku (PH) dijagnozu. Stereotaksična biopsija je neurohirurška procedura kojom se, bez bitnog narušavanja integriteta i funkcije moždanog tkiva, može obezbediti reprezentativni uzorak intrakranijalne tumorske promene radi sprovođenja PH i drugih specifičnih analiza, u cilju postavljanja tačne dijagnoze i potom primene adekvatnog lečenja. Cilj: Cilj ove studije je da se utvrditi mogućnost uzorkovanja reprezentativnog tkiva za postavljanje PH dijagnoze uz pomoć stereotaksične biopsije kod pacijenata sa tumorom mozga, kao i da se utvrdi vrsta i učestalost eventualnih komplikacija same procedure i postojanje korelacije između PH nalaza dobijenog stereotaksičnom biopsijom i rezultata sprovedenih neuroradioloških ispitivanja. Materijal i metode: Sprovedeno istraživanje je bilo kliničko, prospektivno, a uzorak je činilo ukupno 50 pacijenata koji su bili hospitalizovani na Klinici za neurohirurgiju KCV zbog dijagnostikovane tumorske promene mozga i postavljene indikacije za stereotaksičnu biopsiju, u periodu od septembra 2016. godine do januara 2018. godine. Svi pacijenti koji su uključeni u studiju su u sklopu sprovedene dijagnostičke obrade imali načinjen magnetno rezonanantni (MRI) pregled glave na osnovu kojeg su se određivale morfološke karakteristike tumora i vršila procena prirode tumorske promene mozga, a kod ukupno 25 pacijenata je dodatno načinjena MR spektroskopija (MRS) dijagnostikovane tumorske promene sa ciljem određivanja biohemijskog profila i dodatne procene i karakterizacije tkiva. Nakon sprovedene detaljne onkološke obrade i adekvatne pripreme, se sprovodila kompjuterizovanom tomografijom (CT) navođena stereotaksična biopsija sa ramom u cilju uzorkovanja adekvatnog tkiva za PH analizu. U toku istraživanja procena uspešnosti uzorkovanja reprezentativnog tkiva se vršila pregledom bioptata od strane patologa, a nakon procedure se kliničkim pregledom i kontrolnim CT pregledom glave utvrđivao stepen komplikacija. Rezultati: Dobijeni rezultati su pokazali da su fokalni neurološki deficit i moždani sindrom bili najčešći klinički simptomi i znaci kod pacijenata kod kojih je indikovana stereotaksična biopsija tumora mozga. Prema MRI nalazu najzastupljenije su bile difuzne tumorske promene sa 36% udela u uzorku, zatim solitarne sa 34% i multifokalne sa 20%, a potom multicentrične tumorske promene koje su predstavljale 10% uzorka. Takođe, na osnovu MRI i MRS nalaza je oko 80% tumora procenjeno kao najverovatnije glijalnog porekla. U 95,9% slučaja je postavljena precizna PH dijagnoza. Nepromenjeno stanje svesti i neurološki nalaz su imali 92% pacijenata nakon biopsije, a kod 3 pacijenta (6%) je došlo do razvoja prolaznog neurološkog deficita, dok je jedan pacijent (2%) razvio trajan neurološki deficit. Ukupan morbiditet vezan za proceduru je stoga 2%, a nije zabeležen ni jedan smrtni slučaj (mortalitet 0%) tokom sprovođenja studije. Zaključak: Stereotaksična biopsija je dokazana i veoma pouzdana procedura sa malim brojem komplikacija i niskom stopom morbiditeta i mortaliteta, kojom se omogućava dobijanje reprezentativnog uzorka tumorskog tkiva za postavljanje sigurne patohistološke dijagnoze. Intraoperativna PH analiza dela uzorka tkiva dodatno poboljšava uspešnost pri uzorkovanju i postavljanju definitivne PH dijagnoze. Savremene neuroradiološke metode imaju visoku specifičnost u razlikovanju biološke prirode tumorskih promena, ali se ne mogu koristi nezavisno od PH analize uzorka tkivaIntroduction: The implementation of numerous neuroradiological techniques has significantly influenced the way and the efficiency in which the diagnosis of brain tumor is established. Based on non-invasive imaging data, a differential diagnosis can be made, but no neuroradiological method has been established so far, which can finally make a definitive diagnosis. Stereotactic biopsy is a neurosurgical procedure that can provide a representative sample of any intracranial tumor in order to performe histopathological and other specific examinations, and to set the exact diagnosis and then apply adequate treatment, but without significantly impairing the integrity and function of brain tissue. Objective: The aim of this study is to determine the diagnostic value of stereotactic biopsy and ability of providing the representative tissue in order to establish a pathohistological diagnosis in patients with brain tumors. Also, the aim is to determine the type and frequency of possible complications of the procedure itself and the correlation between the pathohistological findings obtained and the results of the conducted neuroradiological examinations. Materials and methods: This research was clinical, prospective and included a total of 50 patients who were hospitalized at the Clinical Center of Vojvodina, from September 2016 to January 2018, due to diagnosed brain tumor for which the stereotactic biopsy is indicated. In all patients magnetic resonance (MRI) examination of the head was used to determine morphological characteristics and assesse the nature of the brain tumor tissue, and in a total of 25 patients MR spectroscopy was additionally made with the goal of determining the biochemical profile and additional tissue assessment and characterization. After detailed oncological assessment, completed laboratory and radiological diagnostics, a CT guided framebased stereotactic biopsy was performed for the purpose of sampling tumor tissue for pathohistological analysis. During the research, the success rate of biopsy in providing the representative tissue and establishing the diagnosis was performed by a pathologist, and after the procedure, a clinical and a control head CT examination was used to review the rate of complications. Results: The results obtained showed that focal neurological deficit and psychoorganic syndrome were the most common clinical symptoms and signs in this study. According to MRI, the most common were diffuse brain tumors with 36% of the sample, then solitary with 34% and multifocal with 20%, followed by multicentric tumors representing 10% of the study sample. Also, based on MRI and MRS findings, approximately 80% of tumors are estimated to be most likely of glial origin. In 95.9% of cases, a complete pathohistological (PH) diagnosis was established. The unchanged neurological status was observed in 92% of patients after biopsy, and 3 patients (6%) developed a transient neurological deficit, while only one patient (2%) developed a permanent neurological deficit. The total morbidity associated with the procedure is therefore 2%, and no deaths (mortality 0%) related to the procedure during the study is recorded. Conclusion: Stereotactic biopsy is highly reliable procedure with a small number of complications and a low morbidity and mortality rate, which allows us to acquire the representative sample of brain tumor tissue and to establish a pathohistological diagnosis. Intraoperative PH analysis of acquired tissue samples further enhances the sampling performance and the setting of definitive PH diagnosis. Modern neuroradiological modalities have a high specificity in distinguishing the biological nature of brain tumors, but they still can not be used independently of the pathohistological analysis of the tissue sample.
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Cohen, Ouri. "In-Vivo Three Dimensional Proton Hadamard Spectroscopic Imaging in the Human Brain." Thesis, 2013. https://doi.org/10.7916/D8639X3V.
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Magnetic resonance spectroscopic imaging (MRSI) is a useful tool for obtaining information on the biochemical processes underlying various pathologies. A widely used multi-voxel localization method is chemical shift imaging (CSI) which uses gradients for phase encoding. Although simple to implement, low in specific absorption rate (SAR) and immune to chemical shift displacement (CSD), it also suffers from some well known drawbacks caused by its sinc-shaped point spread function (PSF). This results in loss of both signal-to-noise ratio (SNR) as well as localization, an effect that is exacerbated at low resolutions. In contrast, an alternative localization method, Hadamard spectroscopic imaging (HSI) benefits from a theoretically ideal PSF and consequently does not suffer from these drawbacks. In this work we exploit the theoretically ideal PSF of HSI encoding to develop a novel three dimensional (3D) multi-voxel MR localization method based on transverse HSI (T-HSI). The advantages of T HSI are that unlike gradient phase-encoding: (i) the volume of interest (VOI) does not need to be smaller than the field-of-view to prevent aliasing; (ii) the number of partitions in each direction can be small, 8, 4 or even 2 at no cost in PSF; (iii) the VOI does not have to be contiguous; and (iv) the voxel profile depends on the available B1 and pulse synthesis paradigm and can therefore, at least theoretically, approach "ideal" "1" inside and "0" elsewhere. Clinical utility of the new method is shown by spectra obtained from the brain of a healthy volunteer. The benefits of T-HSI are demonstrated by a quantitative comparison to CSI of the SNR and localization in a phantom in both one and three dimensions at clinical resolutions. A novel matrix formalism is used to quantify the impact of non-ideal flip angles on T-HSI. The superior PSF of T-HSI is then used to demonstrate the feasibility of scanning regions near or on the skull while limiting the impact of lipid contamination and obtaining quantifiable spectra. A comparison to spectra obtained using CSI is shown for a healthy volunteer. The new method is also used in a clinical pathology: to scan multiple sclerosis (MS) lesions occurring near the skull. To maintain the benefits provided by the PSF of HSI at higher fields, despite its susceptibility to CSD, a additional hybrid sequence is also developed that limits both the SAR and the CSD, regardless of the size of the VOI. A comparison to CSI in a phantom and in-vivo is carried out and spectra obtained from the brain of a healthy volunteer at 3T are shown. Finally, future research avenues involving extension of this research to ultra high fields (7T) are discussed and possible clinical uses are described.
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Osorio, Joseph Anthony. "Development of improved 1H magnetic resonance spectroscopic imaging techniques for brain tumor patients." Diss., 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3274655.
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Chen, Yue. "Three dimensional localization and [1]H magnetic resonance spectroscopic imaging of an animal model of epilepsy /." 1998. http://wwwlib.umi.com/dissertations/fullcit/9824274.
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(7026797), Nicole L. Vike. "Spectroscopic Investigation of a Novel Traumatic Brain Injury Biomarker and Analysis of Neurometabolic Changes in Youth American Football Athletes." Thesis, 2019.
Find full textAbstract:
Recent advances in Magnetic Resonance Imaging (MRI), a noninvasive imaging technique, have spurred the exploration of poorly understood physiological phenomena in vivo. Applications of MRI vary greatly, from anatomical evaluation to complex functional analysis. The body of this dissertation presents four applications of MRI: 1) investigation of a novel traumatic brain injury (TBI) biomarker, 2) analysis of position-specific head acceleration events on neurometabolic profiles in high school football athletes, 3) the first reporting of neurometabolic changes in middle school football athletes, and 4) a novel application of diffusion-weighted imaging (DWI) to characterize implantable drug-delivery depots (Appendix A).
Magnetic resonance spectroscopy (MRS) is an MRI method used to evaluate the metabolic profiles of tissues. Certain brain metabolites (N-acetyl aspartate, myo-inositol, choline, creatine, and glutamate/glutamine) offer unique information regarding brain homeostasis following TBI. When coupled with additional metrics, such as head acceleration events recorded during collision-sport participation, the mechanisms of neurophysiological changes can be further elucidated. Here, player position-specific neurometabolic changes were evaluated in high school and middle school football athletes. Striking differences were noted between linemen and non-linemen as well as high school and middle school athletes.
However, in most clinical cases of TBI, information regarding head acceleration events is unknown and baseline scans are not available.Therefore, it is critical to evaluate candidate biomarkers which increase solely in response to injury. Acrolein, a toxic reactive oxygen species, has been shown to increase following injury to the central nervous system in animal models. Hence, acrolein is a prime TBI biomarker candidate and has been investigated using nuclear magnetic resonance and MRS at 7 Tesla.
Applications of MRI are not limited to the brain, or even tissues. Studies have reported that up to 50% of patients fail to take their medications correctly - resulting in disease progression and medication waste. In situ forming implants (ISFIs) offer an alternative to oral dosage regimens but have not been validated in vivo. Using DWI, ISFIs can be characterized noninvasively and their design can be refined, ultimately improving patient outcomes.
Taken together, MRI is powerful tool that can be used to investigate a wide range of physiological questions. Chapters 2-4 will emphasize efforts to improve TBI diagnostics and better understand neurometabolic changes in youth football athletes. Appendix A offers insights into the DWI-guided characterization of in situ forming implants.
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Andrews-Shigaki, Brian C. "Analysis of segmentation methods for partial volume correction in magnetic resonance spectroscopy voxels." Thesis, 2007. http://hdl.handle.net/10125/20420.
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He, Xuanzi. "Edited magnetic resonance spectroscopy detects an age-related decline in monkey brain GABA levels." Thesis, 2015. https://hdl.handle.net/2144/15623.
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Recent research had shown a correlation between aging and decreasing Gamma-aminobutyric acid (GABA) the primary inhibitory neurotransmitter in the brain. However, how GABA level varies with age in the medial portion of the brain has not yet been studied. The purpose of this study was to investigate the GABA level variation with age focusing on posterior cingulate cortex, which is the 'core hub' of the Default mode network. In this study, 14 monkeys between 4 and 21 years were recruited and MEGA-PRESS to measure GABA level in order to explorea potential link between aging and GABA. Our results showed that a correlation between age and GABA+/Creatine ratio was at the edge of significance (r= -0.523, p=0.081). There was also a near-significant trend between grey matter/ white matter ratio and GABA+/Creatine ratio (r = -0.518, p=0.0848). Meanwhile, the correlation between age and grey matter showed no significance (r= -0.028, p = 0.93). Therefore, age and grey matter/ white matter ratio accounts for different part of R-squared as independent variables for predicting GABA levels. These finding suggest that there the internal neurochemical variation of GABA levels in the nonhuman primate is associated with normal aging and brain structural decline.
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Rakhshani, Fatmehsari Younes. "Designing and Implementing a Portable Near-Infrared Imaging System for Monitoring of Human’s Functional Brain Activity." 2015. http://hdl.handle.net/1993/30245.
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Functional near-infrared spectroscopy (fNIRS) is a non-invasive technique for monitoring of brain functional activity. It uses near-infrared (NIR) light to get the information related to brain hemodynamic response as most of the tissues in the brain are transparent to NIR light.
The main goal of this study was to design, implement and evaluate a continuous-wave near-infrared spectroscopy (CW-NIRS) system for human’s brain cognitive functions. This system is portable, and works with a small rechargeable battery; thus, it may be used for bedside monitoring. In our CW-NIRS system, we used 3 multi-wavelength LEDs and 8 photodiodes (with built-in amplifiers) resulting in 12 channels (voxels). The collected signals of these 12 channels, at a sampling rate of 15 Hz, can be used for 2D image reconstruction to monitor functional brain activity. All LEDs and photodiodes are placed on a flexible printed circuit board (PCB), which covers the forehead to measure hemodynamic response of the prefrontal cortex. We also developed a software in MATLAB for analysis of optical signals recorded by our CW-NIRS system. This software provides 2D image reconstruction and monitoring of changes in concentration of oxygenated ([HbO2]) and deoxygenated ([HbR]) hemoglobin as well as the total hemoglobin ([HbT]) for the 12 channels over the prefrontal cortex (forehead). The software has also an embedded statistical analysis option for analyzing the collected signals and displaying the results.
The developed CW-NIRS system was evaluated on 14 individuals (24±3 years old) on two common cognitive tasks: verbal fluency task (VFT) and color distinction task (CDT). In both tests, we observed that as the cognitive task begins [HbO2] and [HbT] increase and [HbR] decreases, after a few seconds delay. Furthermore, at the end of the tasks as subjects close their eyes in the second rest state, all three hemodynamic signals converge toward baseline ([HbO2] and [HbT] decrease and [HbR] increases). Also, the difference between hemodynamic signals at the rest state and task state was highly significant (p < 9.95e-11) in all 12 channels and in both cognitive tasks. The results confirm the ability of the designed CW-NIRS system to detect functional brain activities.
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Gebhart, Steven Charles. "Liquid-crystal tunable filter spectral imaging for discrimination between normal and neoplastic tissues in the brain." Diss., 2006. http://etd.library.vanderbilt.edu/ETD-db/available/etd-11272006-131802/.
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Pei-YiLin and 林佩儀. "Optical Brain Imaging of Stroke Patients Using Near Infrared Spectroscopy (NIRS) during Bilateral Pedaling." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/91861538811987597377.
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Wei, Mian. "Development of advanced Raman microscopy methods to interrogate the brain." Thesis, 2021. https://doi.org/10.7916/d8-adm1-vq24.
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A central quest in biology is to understand the structure-function relationship of complex biological systems. The brain represents the ultimate complexity of a biological system: (1) the vertebrate brain contains 107-1011 neurons interconnected with glial cells; (2) over tens of diverse cell types are organized in a hierarchical way over an intricate landscape; (3) coordinated electrical and chemical activities of neuronal ensembles generate emergent properties and functions; and (4) each neuron can extend over large volumes with its spatial scales spanning 6 orders of magnitude.
As a result, compared to other organ systems, our understanding of the brain remains primitive and obscure in terms of both its structures and its functions. Accordingly, many grand challenges endure in brain sciences, including comprehensively mapping neuronal wiring of the brain, an exhaustive taxonomy of cell types in the brain, and robust diagnostic and therapeutic strategies for brain diseases. These challenges are difficult to tackle with existing microscopy methods, because general trade-offs prevail between number of colors, imaging depth, spatial resolution, imaging throughput, sensitivity, and specificity.
Therefore, the quest to understand the brain calls for advances and innovations on novel microscopy methods.The evolution of modern Raman microscopy is fundamentally driven by the development of novel spectroscopy methods. The advancement of molecular spectroscopy in turn pushes forward and benefits from, the progress in vibrational probes, labeling chemistry, and sample processing and transformation. In particular, stimulated Raman scattering (SRS) microscopy offers high sensitivity and fast acquisition for biomedical imaging, by harnessing accelerated vibrational transition from stimulated emission. Bio-orthogonal chemical imaging provides chemical specificity and minimal perturbation for visualizing metabolic dynamics of small molecules, by using tiny vibrational probes such as deuterium and alkyne. Electronic pre-resonance SRS (epr-SRS) microscopy further enhances the sensitivity to the nanomolar level for imaging specific proteins, by exploiting electronic pre-resonance of specially designed Raman dyes.
Despite these notable innovations, the imaging depth of these Raman microscopy methods is limited to superficial layers of biological tissues (~100 μm) due to light scattering. This dissertation contributes to the development of advanced Raman microscopy methods for volumetric imaging with extended imaging depth in scattering tissues. For this purpose, we develop a set of tissue clearing strategies tailored to specific Raman imaging modalities. In addition, we develop image analysis methods to extract systems information from volumetric high-dimensional imaging datasets. Equipped with our volumetric imaging and analysis methods, we elucidate intricate structures and functions of the brain at both physiological and pathological conditions, providing implications for brain tumor metabolism and cerebellum development.
Chapter 1 introduces an overview of Raman microscopy with particular emphasis on SRS and epr-SRS microscopies.
Chapter 2 discusses the principles of tissue clearing with special focus on the basis of light scattering, the working mechanisms of different categories of tissue clearing methods, and the rationale underlying the development and evolution of these tissue clearing methods.
Chapter 3 describes the development of volumetric chemical imaging, which brings label-free SRS microscopy, bio-orthogonal chemical imaging, and metabolic imaging to the realm of volumetric imaging with greater than 10-fold depth extension.
Chapter 4 depicts the development of volumetric multiplex imaging, which generalizes epr-SRS microscopy to the territory of volumetric imaging. With this method we achieve one-shot imaging of more than 10 colors over millimeter-thick brain tissues, extending the imaging depth of multiplex protein imaging by 10~100 folds.
Chapter 5 is a manuscript of an ongoing project on imaging nanocarriers for drug delivery across the blood-brain barrier (BBB). We develop a method of correlative multispectral SRS and fluorescence microscopy to image nanoparticles by SRS with multispectral information and particle counting capability and to image tissue context (especially cerebral vasculature) by fluorescence with high specificity. Using this method, we achieve direct imaging of nanocarriers that cross the BBB with definitive spectral evidence and single particle sensitivity. The preliminary results quantifying the proportion of nanoparticles that cross the BBB provide implications that challenge the current understanding of drug delivery to the brain.
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Ayyalasomayajula, Kalyan Ram. "Development and Validation of Analytical Models for Diffuse Fluorescence Spectroscopy/Imaging in Regular Geometries." Thesis, 2013. http://hdl.handle.net/2005/3275.
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New advances in computational modeling and instrumentation in the past decade has enabled the use of electromagnetic radiation for non-invasive monitoring of the physio-logical state of biological tissues. The near infrared (NIR) light having the wavelength range of 600 nm -1000 nm has been the main contender in these emerging molecular imaging modalities. Assessment of accurate pathological condition of the tissue under investigation relies on the contrast in the molecular images, where the endogenous contrast may not be sufficient in these scenarios. The fluorescence (exogenous) contrast agents have been deployed to overcome these difficulties, where the preferential uptake by the tumor vasculature leads to high contrast,making this modality one of the biggest contenders in small-animal and soft-tissue molecular imaging modalities.
In Fluorescence diffuse optical spectroscopy/imaging, this exogenous drug is excited by NIR laser light causing the emission of the fluorescence light. The emitted fluorescence light is typically dependent on the life time and concentration of the exogenous drug coupled with physiology associated with the tissue under investigation. As there is an excitation and emission of the light,the underlying physics of the problem is described by a coupled diffusion equations. These coupled diffusion equations are typically solved by advanced numerical methods, which tend to be computationally demanding.
In this work, analytical solutions for these coupled partial differential equations (PDEs) for the regular geometries for both time-domain and frequency-domain cases were developed. Till now, the existing literature has not dealt with all regular geometries and derived analytical solutions were only for couple of geometries. Here a universally acceptable generic solution was developed based on Green’s function approach that is applicable to any regular geometry. Using this, the analytical solutions for the regular geometries that is encountered in diffuse fluorescence spectroscopy/imaging were obtained. These solutions can play an important role in determining the bulk fluorescence properties of the tissue, which could act as good initial guesses for the advanced image reconstruction techniques and/or can also facilitate the calibration of experimental fluorescence data by removing biases and source-detector variations.
In the second part of this work, the developed analytical models for regular geometries were validated through comparison with the established numerical models that are traditionally used in the diffuse fluorescence spectroscopy/imaging. This comparison not only validated the developed analytical models, but also showed that analytical models are capable of providing bulk fluorescence properties with at least one order of magnitude less computational cost compared to the highly optimized traditional numerical models.
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Juchem, Christoph [Verfasser]. "1H MR spectroscopy and chemical shift imaging of the in vivo brain at 7 Tesla / vorgelegt von Christoph Juchem." 2006. http://d-nb.info/983668671/34.
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Auger, Héloïse. "Techniques de spectroscopie proche infrarouge appliquées à la quantification de paramètres hémodynamiques." Thèse, 2016. http://hdl.handle.net/1866/18896.
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Ce mémoire est séparé en deux volets, tous deux axés sur la spectroscopie proche infra-rouge (NIRS) pour la quantification des paramètres hémodynamiques. La NIRS est principalement basée sur la mesure des coefficients d'absorption (μa) et de dispersion (μs’) des tissus afin de retrouver les concentrations d'oxy- et de déoxyhémoglobine dans le sang. L'imagerie à l'aide de la NIRS est basée sur le parcours des photons à travers le tissu biologique à différentes longueurs d'onde du spectre proche infra-rouge.
Le premier appareil de NIRS dont il sera question est un appareil de spectroscopie résolue dans le temps. Ce type de système retrouve des concentrations absolues d'hémoglobine à l'aide d'un bandeau placé sur la peau d’un sujet, dans ce cas-ci sur le front. Le modèle d’analyse des données permet la séparation des contributions extra-cérébrales et cérébrales aux données. Cette méthode fournit des données plus exactes sur la saturation en oxygène du cerveau, par rapport à un modèle homogène où le signal est contaminé par les couches superficielles. Une étude sur les changements hémodynamiques cérébraux de jeunes adultes pendant une activité physique a été réalisée, et l’article en détaillant les résultats est transcrit au chapitre 2. Le chapitre 3 comprend un retour sur cette étude et aborde les possibilités de travaux futurs.
La seconde partie de mes travaux s’est déroulée sous forme de stage en entreprise durant l’été 2016. Sous la supervision de Dennis Hueber, Ph. D., et Beniamino Barbieri, Ph. D., j’ai effectué des recherches portant sur un appareil de NIRS manufacturé par la compagnie ISS Inc. et dont un prototype se trouve actuellement dans le laboratoire de mon superviseur Mathieu Dehaes, Ph. D. Cet appareil combine deux modalités d’imagerie optique, soit la NIRS dans le domaine des fréquences et la spectroscopie de corrélation diffuse. Le chapitre 4 détaille les tâches que j’ai réalisées durant ce temps, de même que les résultats des analyses que j’ai effectuées.This master’s thesis is separated in two phases, both focused on near infrared spectroscopy for the quantification of hemodynamic parameters. NIRS is based on the measure of absorption (μa) and scattering (μs’) coefficients of tissues in order to recover the oxy- and deoxyhemoglobin concentrations in the blood. Its results are based on the photon propagation in tissue at different near-infrared wavelengths. The first NIRS system used during my studies is a time-resolved spectroscopy system. This device allowed us to retrieve absolute hemoglobin concentrations using a headband placed over the subject’s skin and centered on their forehead. The data analysis model which we used allowed us to separate extra-cerebral and cerebral contributions of the signal. This method yielded quantitative absolute measures of cerebral oxygen saturation as opposed to the traditional homogenous model where the signal is contaminated by superficial layers. A study on cerebral hemodynamic changes in young adults during exercise was conducted, and the published article detailing its results is transcribed in Chapter 2. Chapter 3 includes a review of this study and discusses potential future works. The second part of my research consisted in an industrial internship during the summer of 2016. Under the supervision of Dennis Hueber, Ph. D., and Beniamino Barbieri, Ph. D., I have worked on a NIRS device manufactured by ISS Inc., a prototype of which is currently in the laboratory of my supervisor Mathieu Dehaes, Ph. D. This device combines two NIRS modalities: frequency-domain NIRS and diffuse correlation spectroscopy. Chapter 4 details the work I have performed at ISS and the results of my research and analysis.
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Chamard, Emilie. "Modifications neurométaboliques et microstructurales à la suite d'une commotion cérébrale chez les athlètes féminines." Thèse, 2016. http://hdl.handle.net/1866/16041.
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Beausoleil, Thierry P. "Techniques de spectroscopie proche infrarouge et analyses dans le plan temps-fréquence appliquées à l’évaluation hémodynamique du très grand prématuré." Thèse, 2017. http://hdl.handle.net/1866/20527.
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Kundu, Madan Gopal. "Advanced Modeling of Longitudinal Spectroscopy Data." Thesis, 2014. http://hdl.handle.net/1805/5454.
Full textAbstract:
Indiana University-Purdue University Indianapolis (IUPUI)Magnetic resonance (MR) spectroscopy is a neuroimaging technique. It is widely used to quantify the concentration of important metabolites in a brain tissue. Imbalance in concentration of brain metabolites has been found to be associated with development of neurological impairment. There has been increasing trend of using MR spectroscopy as a diagnosis tool for neurological disorders. We established statistical methodology to analyze data obtained from the MR spectroscopy in the context of the HIV associated neurological disorder. First, we have developed novel methodology to study the association of marker of neurological disorder with MR spectrum from brain and how this association evolves with time. The entire problem fits into the framework of scalar-on-function regression model with individual spectrum being the functional predictor. We have extended one of the existing cross-sectional scalar-on-function regression techniques to longitudinal set-up. Advantage of proposed method includes: 1) ability to model flexible time-varying association between response and functional predictor and (2) ability to incorporate prior information. Second part of research attempts to study the influence of the clinical and demographic factors on the progression of brain metabolites over time. In order to understand the influence of these factors in fully non-parametric way, we proposed LongCART algorithm to construct regression tree with longitudinal data. Such a regression tree helps to identify smaller subpopulations (characterized by baseline factors) with differential longitudinal profile and hence helps us to identify influence of baseline factors. Advantage of LongCART algorithm includes: (1) it maintains of type-I error in determining best split, (2) substantially reduces computation time and (2) applicable even observations are taken at subject-specific time-points. Finally, we carried out an in-depth analysis of longitudinal changes in the brain metabolite concentrations in three brain regions, namely, white matter, gray matter and basal ganglia in chronically infected HIV patients enrolled in HIV Neuroimaging Consortium study. We studied the influence of important baseline factors (clinical and demographic) on these longitudinal profiles of brain metabolites using LongCART algorithm in order to identify subgroup of patients at higher risk of neurological impairment.
Partial research support was provided by the National Institutes of Health grants U01-MH083545, R01-CA126205 and U01-CA086368