The subject of this thesis is the use of Magnetic Resonance (MR) Imaging to quantify biometric MR indices in the Multiple Sclerosis (MS) fixed post-mortem central nervous system (CNS) tissue. Evaluating these indices in fixed tissue allows for the use of histology to verify the findings of MRI. However, it must first be discovered if the indices can be evaluated in fixed post-mortem spinal cord tissue. There is very little literature in this specific area, though some in the fixed brain, the results of which have been assumed to be equivalent in the spinal cord without proof. Therefore, the methodology must first be verified before the consideration of any index as useful and translatable to in-vivo spinal cord. This thesis concentrates on the evaluation of MR relaxometry methods using the indices T1 and T2 by themselves and to evaluate the myelin content of fixed post-mortem CNS tissue. The Carr-Purcell-Meiboom-Gill (CPMG) and Multicomponent Driven Equilibrium Single Pulse Observation of T1 & T2 (mcDESPOT) sequences are used to calculate T1, T2 and the Myelin Water Fraction (MWF) which is believed to be proportional to myelin content in the CNS. This is performed at 3T in a clinical scanner and at 7T in a small animal and wholebody scanner. The methods are first evaluated for use in fixed post-mortem CNS tissue. The two myelin measurement methods are then compared to histological staining if appropriate and where available to verify that the results obtained are proportional to myelin content. The T1 and T2 values in fixed tissue were found to be shortened in fixed tissue, T2 values were so short as to be at the limits of measurement by a clinical scanner, and values converged in white and grey matter, and therefore contrast was found to be limited between these tissues. Proton density images provided the most contrast between tissues. However, even with shortened T2 values, the CPMG sequence was able to identify the myelin water component in fixed tissue. The mcDESPOT algorithm struggled to separate the myelin water component due to clinical scanner limitations and the shortened, converging T1 and T2 values. However, the mcDESPOT algorithm was successful in discerning the myelin water component in the high signal situation of a small bore 7T peclinical scanner. An evaluation was then made of the usefulness of these indices for translation into clinical imaging. The CPMG sequence was found to be proportional to myelin content under all conditions, and therefore useful for disease monitoring in demyelinating diseases. The mcDESPOT sequence, was found to be proportional to myelin in some conditions, and is likely to be useful for monitoring myelination, though the sequence could not be fully validated in this thesis.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2007. / Includes bibliographical references (leaves 95-103). / Diffusion MRI and fMRI have provided neuroscientists with non-invasive tools to probe the functional and structural network of the brain. Diffusion MRI is a neuroimaging technique capable of measuring the diffusion of water in neural tissue. It can reveal histological architecture irresolvable by conventional magnetic resonance imaging methods and has emerged as a powerful tool to investigate a wide range of neuropathologies. fMRI is a neuroimaging technique sensitive to hemodynamics which is indirectly linked to neural activity. Despite the applications of diffusion MRI and fMRI in basic and clinical neuroscience, the underlying biophysical mechanisms of cerebral diffusion and the hemodynamic response remain largely unknown. Also, these neurotechnqiues suffer from low SNR compared to conventional MRI. The challenges associated with the acquisition and interpretation of diffusion MRI and fMRI limit the application of these powerful non-invasive neuroimaging tools to study the functional and structural network of the brain. The purpose of this thesis is three fold; (1) improve the acquisition and reconstruction of the diffusion MRI and fMRI signals and (2) develop an MR-compatible cortical cooling system to reversibly deactivate cerebral glucose metabolism, and (3) apply the cortical cooling system to investigate the effect of cerebral glucose metabolism on cerebral diffusion and the hemodynamic response. First, I describe a novel phased array monkey coil capable of improving the resolution of diffusion MRI (4 fold increase) and fMRI (2 fold increase) in monkeys. Secondly, I present a novel reconstruction method to resolve complex white matter architecture which boosts the sampling efficiency of the diffusion MRI acquisition by 274-377%. / (cont.) Thirdly, I present a MR-compatible cortical cooling system capable of reversibly deactivating cerebral metabolism in monkeys. The cortical cooling system has been applied to study the effect of cerebral glucose metabolism on the cerebral diffusion of water. I use MR temperature maps to quantify the region and degree of deactivation (accuracy of ±1 °C in vivo). Then, I show that reversible deactivation of cerebral glucose metabolism affects the magnitude of cerebral diffusion (12-20%) but not the anisotropy. Finally, I apply the cortical cooling system to study the effect of reversibly deactivating cerebral glucose metabolism in V1 and its effect on the hemodynamic response in the visual system. Reversible deactivation of V1 decreased the hemodynamic response in visually driven regions upstream and downstream from V1. Compensatory effects were observed in V1 in both hemispheres and ipsilateral TEO with in 2 minutes of deactivation. Here I have described the tools to probe the functional and structural network of the macaque brain. / by Mark Haig Khachaturian. / Ph.D.

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No description available.

Microcephaly is neurological condition within which the brain fails to develop to a normal size resulting in the appearance of a smaller head. Microcephaly often accompanies various neurodevelopmental disorders. The corpus callosum is the largest white matter structure in the brain, comprised primarily of heavily myelinated axons. The corpus callosum connects the left and right hemisphere and allows for communication to occur between hemispheres. Using MRI measurements from a sample of 18 microcephalic patients, I analyzed whether the corpus callosum was impacted as a result of microcephaly. When compared to normocephalic controls, the corpus callosum was generally smaller in relation to overall cerebral hemispheric volume, suggesting that white matter brain tissues may be affected by microcephaly. A deeper understanding of the brain through research on the underlying mechanisms responsible for brain evolution and development is critical to our ability to detect, treat and prevent neurodevelopmental, neurodegenerative and psychiatric disorders. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2019. / FAU Electronic Theses and Dissertations Collection

The main strategy for treating solid cancers is based on the very early diagnosis of a malignant tumor, and in general the smaller the tumor, the greater the likelihood of successful treatment. Magnetic Resonance Imaging (MRI), based on the nuclear magnetic resonance phenomenon, provides the possibility of detecting early malignant tumors with the assistance of appropriate contrast agents. Hence, researchers continue to develop novel magnetic materials to achieve this aim. Superparamagnetic nanoparticles have become the focus of these studies because their superparamagnetic, biocompatible and hydrophilic properties would be revealed after modifying the particle surface by suitable surfactants. Considerable research in this area has provided valuable insights; however, suitable magnetic materials that can fulfill all the requirements of MRI application are still under investigation. Surface modification of superparamagnetic nanoparticles towards their use as MRI contrast agents has been the topic for many researchers, but implementation into fully functional in vivo procedures still remains as a challenging task. In the present study, high quality monocrystalline iron oxide nanoparticles have been synthesised and surface-modified with carboxymethylated dextran as well as polyethylene glycol (PEG). Dextran and PEG macromolecules with low and high carboxyl contents were synthesized and grafted onto dopamine-iron oxide nanoparticles. Furthermore, the coating procedure was optimised to prevent aggregation among the nanoparticles. Dextran-coated and PEG-coated nanostructures were characterised by using X- ray Photoelectron Spectroscopy (XPS), Fourier Transformer Infrared Spectroscopy (FTIR), Transmission Electron Microscopy (TEM) and Dynamic Light Scattering (DLS). Consequently, mono-dispersed dextran coated nanoparticles were obtained with an approximate hydrodynamic diameter of 50 nm. The resulting coated nanoparticles exhibited the nanostructures with an excellent colloidal stability in physiological environment even at high salt concentration. The resistance to non-specific protein adsorption was investigated in an in vitro model. Both dextran-coated and PEG-coated nanoparticles displayed low non-specific adsorption. However, the free carboxyl groups could be activated to covalently immobilize proteins. / Thesis (M.Eng.Sc.)--School of Chemical Engineering, 2006.

Thesis (Ph. D.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

Thesis (Ph. D.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

Thesis (M. Phil.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

Thesis (M. Phil.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.