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 15 of 15 for “"multi-echo"”.
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Multi-echo methods for fast MRI and MRS of ³¹P containing compounds
Thesis (Ph. D.)--Massachusetts Institute of Technology, Whitaker College of Health Sciences and Technology, 1997.
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Investigating neuromodulation with theta burst stimulation to primary visual cortex and subsequent effects on resting state networks: A multi-echo fMRI study
Theta burst stimulation (TBS) is a type of rTMS protocol which has the advantage of a shorter delivery time over traditional rTMS. When applied to motor cortex, intermittent TBS (iTBS) has been shown to yield excitatory aftereffects, whereas continuous TBS (cTBS) may lead to inhibitory …
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Say cheese! Brain imaging of texture perception
… intensity or complexity were measured using multi-echo fMRI and fNIRS. Food stimuli were specifically designed to reduce masticatory movements. Further, multi-echo denoising and both univariate and multivariate analysis were implemented for fMRI; while for fNIRS, multiple motion-correction …
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In-vitro Validierung von MRT-Methoden zur Fettquantifizierung bei 1,5 Tesla
… mittels 2-Punkt-Dixon (MR-Bildgebung), Multi-Echo-Dixon (MR-Bildgebung), sowie single-voxel proton (MR Spektroskopie - MRS) mit den Lokalisierungstechniken PRESS und STEAM gemessen. Für die statistische Evaluierung wurden die Ergebnisse mittels linearer Regression und …
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Investigating brain metabolite levels in adolescents living with HIV using atlas-based magnetic resonance spectroscopic imaging (MRSI)
… T1- weighted structural MRI using a multi-echo magnetization-prepared rapid acquisition gradient echo (MEMPRAGE) sequence and volumetric MRSI using spiral-encoded localized adiabatic selective refocusing (LASER) CSI. LCModel was utilized to achieve spec
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Land Cover and Impervious Surface Mapping Using Multispectral Airborne Laser Scanner Data
… impervious surface mapping accuracy. Recently, multispectral airborne lidar sensors have become available which have the ability to scan the ground at three different laser wavelengths simultaneously. The multispectral point cloud has the capability of being used as the sole source of data for …
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Development of MR Thermometry Strategies for Hyperthermia of Extremity and Breast Tumors
… measuring temperature in the fatty tissue using multi-echo fat water separation methods, reducing the error of performing MR thermometry in such tissues. All of these methods were characterized with phantom and in vivo experiments in a 1.5T MR system. </p> <p>The results of this research can …
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FMRI In Patients With Implanted Electrodes: Mitigating Imaging Artifacts
… by the electrodes and calculates the optimal echo times based on the distance from the electrodes, to minimize signal loss. Simulation results showed that optimizing the echo times led to a better contrast-to-noise ratio. A multi-echo approach was also evaluated as a practical implementation …
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MRI techniques for quantitative and microstructure imaging
… MRI typically requires the acquisition of multiple images for biophysical model fitting, which leads to long scan time that consequently causes low SNR, low spatial resolution, image artifacts and vulnerability to motion. This thesis aims at overcoming these challenges by developing novel …
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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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Technical Development of Hyperpolarized [1-13C]Pyruvate Imaging for Clinical Translation
… conditions. However, there are multiple remaining technical limitations to overcome for translating the technique to clinics. In this study, I made three technical advances in imaging hyperpolarized [1-13C]pyruvate and products in humans. First, I measured in vivo T2* of …
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DTI-ALPS REFLECTS WHITE MATTER DIFFUSION ANISOTROPY AND MICROSTRUCTURAL HETEROGENEITY RATHER THAN GLYMPHATIC FLOW: INSIGHTS FROM MULTI-MODAL MRI
… imaging (b=1000 and 2000 s/mm2), and multi-echo gradient-echo sequences for quantitative susceptibility mapping. Within standard centrum semiovale regions of interest, we computed DTI-ALPS together with fractional anisotropy (FA), mean diffusivity (MD), mode of anisotropy (MA), and …
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On Nature of the Gradient Echo MR Signal and Its Application to Monitoring Multiple Sclerosis
<p>Multiple Sclerosis is a common disease, affecting 2.5 million people world-wide. The clinical course is heterogeneous, ranging from benign disease in which patients live an almost normal life to severe and devastating disease that may shorten life. Despite much research, a fully effective …
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Bridging Mri Reconstruction Across Eras: From Novel Optimization Of Traditional Methods To Efficient Deep Learning Strategies
… was acquired at a sub-Nyquist rate with with multiple receiver coils, and the redundancy among these coils were used for image reconstruction. Following the clinical impact and success of PI methods, compressed sensing (CS) techniques were developed to reconstruct images by using …
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A comparison of imaging modalities and decoding methods for detecting semantic information in the brain
… (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 2 I propose a new theoretical framework for describing representations. By posing six questions …