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 “"Echo Planar Imaging"”.
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Distortion correction in magnetic resonance imaging using the simulated point spread function
… distortion is a highly prevalent issue for echo-planar imaging (EPI), due to long readout times and field inhomogeneity. Previously, the measured point spread function (PSF) has been shown to be effective in correcting this distortion. In this work, we reconstruct an image quickly and …
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Quantitative Measurement of Velocity and Dispersion via Magnetic Resonance Imaging
… with rotational symmetry. In addition, an echo planar imaging-based phase contrast sequence can be applied for the direct measurement of the Eulerian velocity fields in more general swirling flows. Longitudinal dispersion measurements in the packed bed and partitioned pipe mixer …
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Implementation of anatomical navigators for real time motion correction in diffusion tensor imaging
… to correct for motion in diffusion tensor imaging. These methods have some limitations and drawbacks. This article describes a novel technique using a three-dimensional-echo planar imaging navigator, of which the contrast is independent of the b-value, to perform prospective motion …
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Gradient characterization in magnetic resonance imaging
… magnetic resonance (MR) scans, such as spiral imaging and echo-planar imaging, require speed and gradient accuracy while putting high demands on the MR gradient system that may cause gradient distortion. Additionally, high field MR scans are prone to inhomogeneities that disturb the gradient …
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Online, low-latency decision making for Fetal Magnetic Resonance Imaging with machine learning
Fetal Magnetic Resonance Imaging (MRI) with T2-weighted Half-Fourier-Acquisition Single-Shot Turbo-Spin-Echo (HASTE) sequence plays an important role in diagnosing brain abnormality. However, the quality of HASTE images routinely suffer from fetal motion which leads to image artifacts, incomplete …
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Simultaneous DTI and rs-fMRI using the navigated diffusion sequence
… dependent (BOLD) functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI) experiments are normally performed separately. The idea of extracting inherently co-registered activation/connectivity maps and diffusion parameters has resulted in efforts to develop methods for …
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Noninvasive Assessment of Tumor Hypoxia Using MRI in Clinical and Preclinical Tumor Models
… measured using Fluorocarbon Relaxometry using Echo Planar Imaging for Dynamic Oxygen Mapping (FREDOM). In addition, BOLD and TOLD MRI measurements were used to predict radiation treatment outcome following a single dose of 30 Gy. BOLD MRI was also assessed in cervical cancer patients in …
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Measurement of Fluid Movement Throughout the Brain via Multiple Magnetic Resonance Imaging Techniques During High-Definition Transcranial Direct Current Stimulation
… goal of this study was to use Diffusion Tensor Imaging (DTI) and pulsed-Arterial Spin Labeling (pASL) to target interstitial fluid diffusion within the brain parenchyma as well as blood perfusion of brain tissue, respectively, with and without intervention of bi-frontal 4mA anodal tDCS. The MRI …
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Real-time motion and magnetic field correction for GABA editing using EPI volumetric navigated MEGA-SPECIAL sequence: Reproducibility and Gender effects
… In this work, a pair of three-dimensional (3D) echo planar imaging (EPI) volumetric navigators (vNav) with different echo times, were inserted in MEGA-SPECIAL to perform prospective correction for changes in the subject's head position and orientation, as well as changes in B0. The navigators do …
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Development of Advanced Mr-Guided Adaptive Radiation Therapy Methods For Head & Neck Cancers On The 1.5T Mr-Linac
… tumor response as measured through quantitative imaging techniques such as diffusion-weighted imaging (DWI). The aims of this dissertation are to validate the existing adaptive workflows for HNC on the MR-linac and perform technological validation of preliminary steps for these advanced ART …
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Parallel transmit pulse sequence design for ultra-high field (7T) MRI
… 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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Hyperpolarized Nuclei for NMR Imaging and Spectroscopy – Methodology and model studies of lung and vascular function
… magnetic resonance (NMR), magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) are widely used methods in medical diagnostic imaging and biological research. Clinical MRI has been restricted to imaging of protons, for reasons of sensitivity. In recent years, …
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Quantitative susceptibility mapping and susceptibility-based distortion correction of echo planar images
… continues to expand as magnetic resonance imaging (MRI) technology advances through increases in field strength and the development of new image acquisition and reconstruction methods. The advent of echo planar imaging (EPI) has allowed volumetric data sets to be obtained in a few seconds, …
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Noise reduction during diffusion tensor imaging of infants
Acoustic noise produced during echo planar imaging (EPI) has been known to reach excessive levels. In addition to causing general patient discomfort and anxiety, this level of noise makes the scanning of young children and infants particularly difficult. Infants are typically scanned while sleeping …
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Magnetic Resonance Spectroscopy Imaging of 2-Hydroxyglutarate in Brain Tumors at 3T and 7T In Vivo
… is a significant breakthrough in neuro-oncology imaging. 2HG is the first imaging biomarker that is specific to a genetic mutation in gliomas, making the diagnosis of IDH mutant gliomas possible without biopsy. 2HG also has a significant predictive value with respect to the stage and survival in …
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Strategies for Artifact Correction and Motion Monitoring in MRI Through Innovations in Radiofrequency Coil Design
… on the same coil, localized B_0 shimming and MR imaging can be performed with the same coil array. This technology, referred to as an integrated parallel reception, excitation, and shimming (iPRES) coil array, was previously used to correct for distortions in spin-echo echo-planar imaging (EPI) …
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Temperature Mapping using Mid-Field Magnetic Resonance Imaging
Magnetic Resonance Imaging (MRI) is a non-invasive imaging modality with excellent soft tissue contrast and sensitivity to tissue temperature. MRI use is growing in Canada with expectation that this is expected to continue in the medium term, with more wide adoption of MRI and in particular a …
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Real time motion tracking in image guided focused ultrasound intervention
… to the structures of volunteer livers in the MR echo planar imaging (EPI) scans. An experiment setup, in which the tissue mimicking phantoms was controlled to move reciprocally, was designed. The off-line MATLAB algorithm based on cross correlation proved to have an acceptable error less than 1.0 …
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Self-navigated prospective motion correction of repeated 3D-EPI acquisitions for functional MRI applications
Functional magnetic resonance imaging (fMRI) typically employs one of the fastest pulse sequences – known as echo-planar imaging (EPI) – to repeatedly image the whole brain as stacks of two-dimensional slices. Two-dimensional EPI (2D-EPI) is preferred over threedimensional (3D)-EPI as it is more …