Diss. (sammanfattning) Stockholm : Karol. inst. / Härtill 5 uppsatser.

Lic.-avh. (sammanfattning) Linköping : Linköpings universitet, 2006. / Härtill 3 uppsatser.

Tai, Chi Kin. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (p. 56-59). / Abstracts in English and Chinese. / Chapter 1 --- Introduction --- p.7 / Chapter 2 --- Theoretical Background --- p.9 / Chapter 2.1 --- Nuclear Magnetic Resonance --- p.9 / Chapter 2.1.1 --- Nuclear spin and macroscopic magnetization --- p.10 / Chapter 2.1.2 --- Precession and Larmor Frequency --- p.12 / Chapter 2.1.3 --- Radio-frequency excitation --- p.13 / Chapter 2.1.4 --- Radio-frequency relaxation --- p.15 / Chapter 2.1.5 --- Spin echoes --- p.17 / Chapter 2.1.6 --- Contrast mechanisms --- p.17 / Chapter 2.2 --- Magnetic Resonance Imaging --- p.20 / Chapter 2.2.1 --- MRI machine hardware --- p.20 / Chapter 2.2.2 --- Slice selection --- p.22 / Chapter 2.2.3 --- Frequency encoding --- p.23 / Chapter 2.2.4 --- Phase encoding --- p.26 / Chapter 2.2.5 --- Pulse sequences --- p.26 / Chapter 2.2.6 --- Field of view and resolution --- p.28 / Chapter 3 --- Parallel Magnetic Resonance Imaging --- p.30 / Chapter 3.1 --- Motivation --- p.30 / Chapter 3.1.1 --- Aliasing --- p.31 / Chapter 3.2 --- Coil array and coil sensitivities --- p.32 / Chapter 3.3 --- Sensitivity encoding --- p.32 / Chapter 3.3.1 --- Estimation of coil sensitivities --- p.33 / Chapter 3.3.2 --- SENSE reconstruction --- p.33 / Chapter 3.4 --- pMRI reconstruction by TV regularization --- p.35 / Chapter 3.4.1 --- Model for coil images --- p.35 / Chapter 3.4.2 --- Total variation-regularization approach --- p.36 / Chapter 4 --- Reconstruction Results --- p.39 / Chapter 4.1 --- Simulation --- p.39 / Chapter 4.1.1 --- Reconstruction quality --- p.41 / Chapter 4.1.2 --- Reconstruction results --- p.43 / Chapter 4.2 --- MRI phantom experiments --- p.44 / Chapter 4.2.1 --- Reconstruction quality --- p.48 / Chapter 4.2.2 --- Reconstruction results --- p.49 / Chapter 4.3 --- In-vivo MRI images --- p.51 / Chapter 5 --- Discussions and Conclusions --- p.54 / Bibliography --- p.56

This thesis presents methods for quantitative MRI analysis of brain injury, repair and degeneration in multiple sclerosis (MS) that provide new insights into disease pathogenesis and evolution. / Demyelinated and inflammatory white-matter lesions are hallmark features of MS. A methodology is described to detect regions of acute white-matter lesions that undergo myelin destruction and repair based on analysis of magnetization transfer ratio (MTR) images. Validation is performed based on histopathology and error is assessed based on same-day scans. To quantify the spatial extent and temporal evolution of myelin destruction and repair, data from a 3-year clinical trial is analyzed using this method. Approximately 20% of acute lesion voxels show some repair over the initial 7 months. In subsequent months, there is little further repair, but some increases in the lesion volume undergoing demyelination. / Although less conspicuous on conventional MRI, there is considerable MS pathology in the brain tissue outside of white-matter lesions. An image-processing methodology was developed to obtain accurate metrics that quantify change over time in whole-brain MTR (associated with changes in myelin-density) and in T2 relaxation time (associated with changes in inflammatory edema). These metrics, in addition to metrics of brain atrophy and axonal integrity, were used to quantify brain injury and degeneration following immunoablation and autologous hematopoietic stem cell transplantation therapy for MS. Pronounced brain volume loss was detected immediately following therapy, associated with decreased myelin density and not resolution of edema. / Post-mortem histopathology has revealed abnormalities in the cortical grey-matter of MS patients that appear to be independent of white-matter lesions. A methodology to quantify neocortical injury and degeneration that yields cross-sectional and longitudinal metrics of cortical thickness and grey-matter/white-matter interface integrity both globally and regionally is presented and validated. MS patients with progressive disability showed greater decreases in cortical metrics compared to MS patients with stable disability. / The quantitative MRI analysis methods presented in this thesis are applicable to MRI data obtained in clinical trials of therapies for MS, have the necessary sensitivity and specificity to assess therapeutic efficacy, and provide new insights into disease pathogenesis and evolution.

This study was designed to clarify some of the issues surrounding the nature of hemispheric contributions to the processing of emotional and linguistic prosody, as well as to examine the relative contribution of different sensory modalities in processing prosodic structures. Ten healthy young participants were presented with semantically neutral sentences expressing affective or linguistic prosody solely through the use of non-verbal cues (intonation, facial expressions) while undergoing tMRI. The sentences were presented under auditory, visual, as well as audio-visual conditions. The emotional prosody task required participants to identify the emotion of the utterance (happy or angry) and the linguistic prosody task required participants to identify the type of utterance (question or statement). Core peri-sylvian, frontal and occipital areas were activated bilaterally in all conditions suggesting that processing of affective and linguistic prosodic structures is supported by overlapping networks. The strength of these activations may, in part, be modulated by task and modality of presentation.

Brain atrophy has been used as a marker for disease progression in Multiple Sclerosis (MS). SIENA, an automated tool for measuring brain volume change, was tested to see whether MRI slice thickness and gap presence affect longitudinal atrophy measures. Isotropic global scan-rescan images were used to simulate 3 mm and 5 mm axial slice thicknesses with 1 and 2mm gaps, respectively. SIENA remained accurate and precise with increasing slice thickness and gap presence. Furthermore, symmetric pre-registration was crucial for scans with larger slice-thickness and gaps. / SIENA was used to observe atrophy in children who have experienced a Clinically Isolated Syndrome (CIS) of the type leading to MS (CIS-MS). Brain atrophy was present within the first three months after a CIS event, and then subsided over the rest of the year. If the first acute episode was excluded, there was no significant difference in atrophy rates between the CIS-MS group and the CIS group, and no significant difference between those with T2-weighted brain lesions versus those who had none.

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