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 16 of 16 for “"High field MRI"”.
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ΔB₀ Field Control in High Field MRI with Local Multcoil Shim Arrays
… fabricate, and physically small, static magnetic field control in magnetic resonance imaging. The presented thesis will show frameworks for coil current calculation for homogeneity and novel selective excitation applications. As MRI RF coils trend towards repositionable and flexible systems for …
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Altered Brain Networks In Patients with Psychogenic Non-Epileptic Seizures (PNES) Using Ultra High Field MRI
… Participants underwent 7T resting-state fMRI scanning. Independent Components Analysis (ICA) and whole brain functional connectivity making use of region of interest analysis (ROI) was used to study the default mode network and the salience network. Results: No Significant differences in …
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Mitigating Inhomogeneity in High-Field MRI Excitations: Arbitrary Waveform Optimization and Multiphoton Parallel Transmission (MP-pTx)
High-field magnetic resonance imaging (MRI) using a standard volume coil results in a spatially varying flip angle across the body, which renders images difficult to clinically interpret. This arises from the complex interactions of electromagnetic fields from current-carrying elements surrounding …
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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
… diseases.</p> <p>Magnetic resonance imaging (MRI) is a noninvasive imaging technique which facilitates detection of brain lesions and visualization of the brain overall. However, limitations in contrast and resolution at clinical field strengths may hinder investigation of the underlying …
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Reed-Relay Switched Tuning Circuit for Stretchable RF Coils in Low Field, Portable MRI
While MRI (Magnetic Resonance Imaging) technology allows us to get detailed images of the inside of a subject’s body, it most commonly requires very expensive and large-scale machinery which limits the scenarios it can be used in. These types of costly MRI are usually high-field MRI, which operates …
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Improved accuracy in susceptibility-based OEF measurements by mitigation of partial-volume effects via combined magnitude and phase reconstruction
… the magnitude and phase of the complex-valued MRI signal. This method is validated both in numerical simulations and on in vivo data. The ability to perform high-quality fetal brain imaging is hampered by motion of the fetus, which can severely degrade image quality. Previously, low-resolution …
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Utilisation of novel magnetic resonance imaging features in the diagnosis and understanding of multiple sclerosis
… including magnetic resonance imaging (MRI), interpreted in accordance with diagnostic criteria, to demonstrate the requisite dissemination of lesions in (anatomical) space and time. Lesions comprising inflammatory demyelination in the central nervous system are a core pathological …
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Off-resonance and detuned surface coils for B₁ inhomogeneity in 7-Tesla MRI
A problem with high-field MRI is the lack of B1 homogeneity, particularly signal cancellation in the outer parts of the head. Here we attempt to correct this by adding surface coils. To adjust the mutual coupling, we vary the resonance properties of the added coil. A new agar-based head phantom was …
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Magnetic Resonance Imaging in Paediatric Coronary Vasculopathy
… detection and therefore, prevention of disease. MRI has the potential to achieve this by imaging coronary lumen, vessel wall and central vascular stiffness in a child-friendly free-breathing protocol lasting thirty minutes. Methods A three-dimensional steady-state-free-precession [3D SSFP) …
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Numerical field simulation for parallel transmission in MRI at 7 tesla
… manifest as center brightening, for high-field magnetic resonance imaging (MRI). Parallel transmission achieves spatially-tailored pulses through multiple radiofrequency (RF) excitation coils that can be activated independently. In this work, simulations of magnetic fields in …
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MRI-compatibility enhancements to USM performance for interventional devices in MR environments
… safe performance of magnetic resonance imaging (MRI)-guided robot-assisted interventions requires full control and high precision of assistive devices and tools. Because many currently available tools are not MRI-compatible, the characterization of existing tools and development of new ones are …
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Comprehensive MRI Safety Assessment: Impact of Strain-Relief Loop Position, Lateral Movement, and Varying Field Strengths on RF-Induced Heating of Medical Implants
Magnetic Resonance Imaging (MRI) utilizes strong magnetic fields and radiofrequency (RF) waves to produce detailed images of human organs, tissues, and various anatomical structures. Despite its benefits, individuals with active implantable medical devices (AIMDs) and passive implantable medical …
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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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Improving Data Quality for High Resolution Functional MRI in Cognitive Neuroscience Applications
… the first successful Magnetic Resonance Imaging (MRI) image 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 …
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Parallel transmission for magnetic resonance imaging on a 9.4 Tesla Human System.
… been increasingly pushing towards using ultrahigh magnetic field (7 Tesla and higher) for magnetic resonance imaging in human to benefit from substantial increases in signal to noise ratio and contrast. However, at ultrahigh field, severe transmit B1 (B1+) inhomogeneity occurs, limiting …