Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 20 for “"ultra-high field"”.
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Ultra-high field (7T) magnetic resonance fingerprinting
Ultra-high field (7T+) magnetic resonance imaging (MRI) improves image quality substantially compared to normal clinical 1.5T or 3T MRI. However, 7T MRI brings new challenges pertaining to B1+ inhomogeneity, B0 inhomogeneity, increased spectral bandwidth, and RF heating. Quantitative parametric …
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Parallel transmit pulse sequence design for ultra-high field (7T) MRI
Ultra-high field (UHF, B0 ≥ 7 T) magnetic resonance imaging (MRI) scanners allow more sensitive, faster and higher resolution imaging than clinical MRI systems at 1.5 T and 3 T. However, radiofrequency field (B+ 1) inhomogeneities can cause signal dropouts in UHF MRI. The most flexible solution to …
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Design and manufacture of an ultra-high field ex vivo coil assembly
Magnetic Resonance based architectonic segmentation aims to detect variations in brain architecture that may provide incredible insight into diseases such as epilepsy, schizophrenia, dyslexia, and autism. Data from ex vivo scans is necessary for the development of automatic methods to detect these …
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Altered Brain Networks In Patients with Psychogenic Non-Epileptic Seizures (PNES) Using Ultra High Field MRI
Background: Psychogenic Non-epileptic Seizures (PNES) are attacks that appear similar to epileptic attacks. However, they lack abnormal electrical discharges in the brain and have psychological underpinnings and causes. The gold standard of diagnosis is video-EEG which is not widely accessible, …
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A study of ultra-high field strength structural and spectroscopic MR imaging in dementia with Lewy bodies and Alzheimer’s disease
… to cognitively healthy older adults, using ultra-high field, 7 tesla (7T), brain magnetic resonance imaging (MRI) and single voxel proton magnetic resonance spectroscopy (MRS). First, I conducted systematic reviews of the AD and DLB, MRI and MRS literature, demonstrating that DLB is …
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Ultra-high Field MRI Methods for Precise Anatomical and Spectroscopic Measurements in the Brain and Application to Neurological and Neuropsychiatric Diseases
… in contrast and resolution at clinical field strengths may hinder investigation of the underlying biological mechanisms of these diseases. Ultra-high field MRI scanners, such as those at 7-Tesla, can enhance biomarker detection because they provide superior contrast, resolution, and …
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Bilateral Ortohogonality Generative Acquisitions Method for Transmit Field Inhomogeneity Correction in Magnetic Resonance Imaging
Ultra-high field (>7T) magnetic resonance imaging (MRI) systems result in higher intrinsic signal to noise ratio compared to the lower field systems and have been previously utilized for acquisition of high-resolution images and reducing scan time. However, transmit field inhomogeneity of …
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Utilisation of novel magnetic resonance imaging features in the diagnosis and understanding of multiple sclerosis
… system are a core pathological feature of MS. Ultra-high field (e.g. 7 Tesla or 7T) T2*-weighted MRI can demonstrate in vivo a central vein in most of these lesions. This is a histopathologically specific feature which could be exploited to improve diagnostic workup in cases of suspected …
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¹H-MRSI at 7T using spectral-selective binomial excitation and adiabatic refocusing
… due to the inherently low sensitivity of MRSI. Ultra-high field systems such as 7T can provide higher SNR and better spectral separation of metabolite peaks, but they also introduce pronounced B₀ and B₁ field inhomogeneity, larger chemical shift displacement error (CSDE), stricter specific …
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Neural computation of depth from binocular disparity
… develop physiologically plausible receptive fields, and predict neural responses to highly unnatural stimuli commonly used in the laboratory. They do not necessarily relate to our experience of depth, but seem to act as a bottleneck for depth perception. Conversely, neural activity in …
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Integral Equation-Based Inverse Scattering and Coil Optimization in Magnetic Resonance Imaging
… been to steadily increase the static magnetic field strength and hence the frequency of operation, resulting in higher available signal-to-noise ratio that could be traded for shorter scan times and increased image quality. In the ultra-high field regime (≥7T), since the radiofrequency …
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Studies On The Physicochemical Properties Of Eu2+ Cryptates: Implications To Contrast Agents For Magnetic Resonance Imaging
… complexes decreases as field strength increases, and in the ultra-high field strength regime, the relaxivity of these complexes is decreased considerably. Because of the slow water-exchange rate of most Gd<sup>3+</sup>-containing complexes (∼;10<sup>6</sup> …
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IMAGING THE GLUTAMATERGIC SYSTEM WITH GLUCEST MRI: CYTOARCHITECTURE, AGING, AND INTERVENTION
… including aging and major depressive disorder. Ultra-high field 7T glutamate-weighted chemical exchange saturation transfer (GluCEST) imaging is emerging as a promising biomarker for in vivo glutamatergic function. This work addresses critical gaps in the literature and explores glutamatergic …
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Being Alone: Social Disconnection in Adolescence
… aged 16-24 years reporting particularly high levels. This vulnerability during a sensitive window of social and emotional development is concerning given that loneliness strongly predicts mental and physical health outcomes. Despite being one of the loneliest age groups, adolescents …
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Slice-selective parallel transmit magnetic resonance imaging at 7T
Ultra-high field (UHF) Magnetic resonance imaging (MRI) at 7 Tesla and beyond provides gains in signal-to-noise ratio (SNR), enabling faster and higher-resolution imaging. However, UHF MRI comes with significant technical challenges, especially radiofrequency (RF, or B+1 ) field inhomogeneity which …
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Flux Pumping for No-Insulation High Temperature Superconducting REBCO Magnets
The high temperature superconducting (HTS) REBCO magnet has many advantages compared to the low temperature superconducting (LTS) magnet, including high operating temperature, high critical current under high magnetic fields, and strong mechanical properties. Due to these excellent properties, HTS …
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Improving Data Quality for High Resolution Functional MRI in Cognitive Neuroscience Applications
… was produced by Paul Lauterbur in 1973, the field of MRI has been improving by leaps and bounds. The number of MRI and functional MRI (fMRI) papers have sky rocketed over the last decade, alongside with advancements in MRI field strength and techniques. In this thesis, I explore various …
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Brain dynamics of behavioral state transitions across sleep and wakefulness
… unknown about how the brain traverses through high and low arousal states. To address this question, we systematically evaluated the relationship between brain activity and arousal state from two angles. First, we centered on the moment that behavioral responsiveness returns with awakening and …
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The Neural Underpinnings of Obsessive-Compulsive Disorder: From Adolescence to Adulthood
… gap, I apply a multimodal approach combining ultra-high field magnetic resonance spectroscopy (7T MRS), resting-state functional MRI (rs-fMRI), and behavioural paradigms to identify neurochemical markers, network-level disruptions, and behavioural signatures of compulsivity in individuals aged …
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Applications of Machine Learning to Neuroimage Analysis in Cerebral Small Vessel Disease
… are particularly well suited for analysing high-dimensional data such as MRI images. This thesis aimed to investigate how machine learning can be applied to neuroimage analysis in CSVD research, focusing on advancing both CSVD assessment and prognosis. Specifically, I explored how ML can be …