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 45 for “"7T"”.
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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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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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Magnetic resonance spectroscopic imaging using parallel transmission at 7T
… designed for new RF excitation hardware at 7T, so-called parallel transmission (pTx). The B1 homogeneity of the pTx excitations improved at least by a factor of 4 (measured by the normalized spatial standard deviations) compared to conventional single channel transmit systems. The first …
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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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¹H-MRSI at 7T using spectral-selective binomial excitation and adiabatic refocusing
… 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 absorption rate (SAR) constraints, …
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High resolution magnetic resonance spectroscopic imaging of the brain from 3T to 7T
Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2024-08-01
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Magnetic Resonance Spectroscopy Imaging of 2-Hydroxyglutarate in Brain Tumors at 3T and 7T In Vivo
… imaging of 2HG in patients at 3T and 7T. A new echo-planar spectroscopic imaging (EPSI) readout was designed incorporating dual-readout alternated gradients (DRAG-EPSI). At 7T, DRAG-EPSI was utilized for increasing the spectral width for fully covering the spectral region of interest, …
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Fast simulation of E1, B1 and Specific Absorption Rate for 7T MRI with the use of graphical processors
Specific Absorption Rate (SAR) is a dominant constraint in high field MR, and has been a topic of much recent interest with developments of parallel transmission systems (pTx). While real-time estimates of local SAR over large volumes as well as SAR-constrained pTx RF design are highly desirable …
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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
… 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 under-represented in high (3T) and …
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Quantifying Neuromelanin Content Across Varying Magnetic Field Strengths: A Comparative Analysis
… of high field strength imaging, e.g., 7 Tesla (7T) provides the opportunity to study neuromelanin production sites with higher spatial resolution and enhanced detail. Since NM-MRI research has not been conducted with high field strength imaging platforms, it is unknown whether the techniques …
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Improving Data Quality for High Resolution Functional MRI in Cognitive Neuroscience Applications
… data quality for high resolution fMRI in 3T and 7T MRI scanners. Firstly, I studied the effect of Prospective Motion Correction (PMC) on 3T data using a simple visual paradigm. In contrast to most conventional techniques that use retrospective motion correction (RMC), PMC collects real-time …
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Parallel radiofrequency transmission for 3 Tesla and 7 Tesla magnetic resonance imaging
… work, a framework to apply pTx to 3T fetal and 7T brain imaging is developed to address the image shading and high SAR issues. Fetal imaging where a large pregnant torso is imaged rapidly to avoid fetal motion artifacts, suffers from similar levels of image shading and imaging limitations by SAR …
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Numerical field simulation for parallel transmission in MRI at 7 tesla
… at main magnetic field strengths of 3T and 7T to demonstrate center brightening associated with head imaging at high magnetic field strengths. Measurements of a circular ROI centered in the image show more B1+ inhomogeneity at 7T than at 3T. The B1* profile is then simulated for a numerical …
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Nucleoside and oligonucleotide approaches towards potential HIV chemotherapies
… investigated. Synthesis of the sequences d(Tp)7T, d(Tps)7T and the base-sensitive d(Tp)3(CBzp)2(Tp)2T was achieved using the silyl-linked solid support in a fluoride-induced cleavage/deprotection strategy.
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A comparison of imaging modalities and decoding methods for detecting semantic information in the brain
… 7 tesla functional magnetic resonance imaging (7T-fMRI) to detect semantic representations; and (3) to evaluate the strengths and limitations of multivariate analysis methods, in particular methods based on regularised regression, for revealing properties of semantic representations. In Chapter …
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The Neural Underpinnings of Obsessive-Compulsive Disorder: From Adolescence to Adulthood
… 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 16–21. A particular focus is placed on the …
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Excitation and readout Designs for high field spectroscopic imaging
… of excitation methods for high field system (7T parallel transmit (pTx) system) and fast readout and post-processing methods to reduce the lipid contamination to the brain. The contributions include fast B1+ mapping and pTx RF pulse design with the local SAR constraints for excitation. …
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Models for meson-deuteron scattering in the resonant region
… in <r-2>d reported in the analysis of 7T+d total cross sections around 1 GeV / c and could introduce small peaks into the deduced 1=0 channel of the k+n cross section. Nevertheless, for the k+d data of Cool et ale conclusions drawn by following the usual folding procedures are not …
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Phase-based regional oxygen metabolism in magnetic resonance imaging at high field
… method to high-field human imaging at 7 Tesla (7T), which allows us to take advantage of improved signal-to-noise ratio (SNR) for the same scan duration to achieve higherresolution analysis of vessels of interest. While the higher field strength poses additional challenges, such as increased …
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Feasibility Study of Multi-application, Multi-Walled Carbon Nanotube for Magnetic Resonance Temperatrue Imaging Guided Laser Induced Thermal Therapy
… (fiber-optic and external laser beam) in a 7T MRI small animal scanner (Bruker Biospin). The 3D MRTI at 7T field strength provides high temporal resolution with reasonable special resolution, as well as accurate 3-D volume temperature measurement. Phantom results show that the …
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