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Investigation of left ventricular heart structure and functions using magnetic resonance diffusion tensor imagingWu, Yin, January 2008 (has links)
Thesis (Ph. D.)--University of Hong Kong, 2008. / Includes bibliographical references. Also available in print.
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Developments in the use of diffusion tensor imaging data to investigate brain structure and connectivity : a thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Medical Physics in the University of Canterbury /Chappell, Michael H. January 2007 (has links)
Thesis (Ph. D.)--University of Canterbury, 2007. / Typescript (photocopy). Includes bibliographical references (leaves 153-172). Also available via the World Wide Web.
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Spatial normalization of diffusion models and tensor analysisIngalhalikar, Madhura Aditya. Magnotta, Vincent A. January 2009 (has links)
Thesis supervisor: Vincent A. Magnotta. Includes bibliographic references (p. 93-101).
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Quantitative in vivo assessment of tissue microstructure using diffusion tensor and kurtosis imagingZhang, Zhongping, 张忠平 January 2011 (has links)
published_or_final_version / Diagnostic Radiology / Master / Master of Philosophy
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Magnetic resonance diffusion characterization of brain diseases丁莹, Ding, Ying January 2012 (has links)
Magnetic resonance imaging (MRI) is a valuable imaging technique. It provides excellent soft tissue contrast and multi-parametric non-invasive imaging protocols. Among those various techniques, diffusion MRI measures the water diffusion properties of biological tissue. It is a useful tool in characterizing various brain tissue microstructures quantitatively. With its rapid development, it is emerging that subtle changes can be probed by diffusion tensor imaging (DTI) quantitation. The objectives of this doctoral work are to access the subtle microstructural alterations in rodent brains due to hemodynamic changes, fear conditioning and sleep deprivation using in vivo DTI. With the improved reproducibility and specificity achieved by using advanced post-processing and animal preparation procedures, in vivo DTI is expected to be useful to explore the underlying biological mechanisms for posttraumatic stress disorder and memory deficit following sleep loss in human.
Firstly, as DTI could be influenced by the presence of water molecules in brain vasculature, for better understand the reproducibility and sensitivity of in vivo DTI measurements, conventional DTI protocol was applied to a well-controlled rat model of hypercapnia. Our data demonstrated that diffusivities increased in whole brain, gray and white matter regions in response to hypercapnia. These results indicate that in vivo DTI quantitation in brain can be interfered by vascular factors on the order of few percents. Cautions should be taken in designing and interpreting quantitative DTI studies as all DTI indices can be potentially confounded by physiologic conditions, cerebrovascular and hemodynamic characteristics.
Secondly, recent DTI studies have shown detection of long-term neural plasticity weeks to months following relatively extensive periods of training in animals. However, rapid plasticity within a short period (24 hours) after learning is important for observing the time course of training-evoked changes and narrow down candidate mechanisms. Fear conditioning (FC), which typically occurs over a short timescale (in minutes), was selected as a paradigm for investigation. Using voxel-wise repeated measures analysis, FA was found to increase in amygdala and decrease in hippocampus 1-hour post-FC, and it reversed in both regions 1-day post-FC. Results indicate that DTI can detect rapid microstructural changes in brain regions known to mediate fear conditioning in vivo. DTI indices could be explored as a translational tool to capture potential early biological changes in individuals at risk for developing post-traumatic stress disorder.
Thirdly, in vivo DTI was employed to access regional specific microstructural changes following rapid eye movement sleep deprivation (SD), and explore possible temporal differentiation of these changes. With voxel-base analysis, MD is found to decrease in post-SD time points in bilateral hippocampi and cerebral cortex. The distributions of these clusters exhibited differentiable layer specific patterns, which were pointing to dentate gyrus and CA1 layer in hippocampus, and parietal cortex and barrel field layers in cerebral cortex. Results indicate that in vivo DTI is capable to detect microstructural changes in specific layers and reveal temporal distinction between them. These specific layers are possibly more susceptible to sleep loss, and the temporal distinction of changes between these layers might underlie learning and memory decline after SD. / published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy
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In vivo DTI study of rodent brains during early postnatal development and injuriesLau, Ho-fai. January 2008 (has links)
Thesis (M. Phil.)--University of Hong Kong, 2009. / Includes bibliographical references (leaves 66-73) Also available in print.
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Magnetic resonance diffusion tensor imaging for neural tissue characterizationHui, Sai-kam. January 2009 (has links)
Thesis (Ph. D.)--University of Hong Kong, 2009. / Includes bibliographical references (leaves 97-111). Also available in print.
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Investigation of left ventricular heart structure and functions using magnetic resonance diffusion tensor imagingWu, Yin, 吳垠 January 2008 (has links)
published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy
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Magnetic resonance diffusion tensor imaging for neural tissue characterizationHui, Sai-kam., 許世鑫. January 2009 (has links)
published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy
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Neurological Models of DyslexiaDailey, Natalie S., Dailey, Natalie S. January 2016 (has links)
The reading network is only partially understood and even less is known regarding how the network functions when reading is impaired. Dyslexia is characterized by poor phonological processing and affects roughly 5-12% of the population. The Dorsal-Ventral and Cerebellar-Deficit models propose distinct behavioral and structural differences in young adults with dyslexia. Behavioral assessments were used to determine if deficits for young adults with dyslexia were restricted to the literacy domain or dispersed among reading and associated behavioral domains. Diffusion tensor imaging (DTI) was used determine the extent to which white matter pathways and gray matter regions differ structurally in young adults with dyslexia. The present study also investigated whether brain-behavior relationships exist and are consistent with the theoretical models of reading in this population. Findings show that young adults with dyslexia exhibited deficits in both literacy and associated behavioral domains, including verbal working memory and motor function. Structural findings showed increased fractional anisotropy in the left anterior region (the aslant) and decreased fractional anisotropy in left posterior regions (inferior occipital fasciculus and vertical occipital fasciculus) of the reading network for young adults with dyslexia. Brain-behavior associations were found between the right inferior frontal gyrus and decoding for those with dyslexia. These findings provide support for the use of an altered reading network by young adults with dyslexia, as outlined by the Dorsal-Ventral model of reading. Limited structural and behavior findings support of the Cerebellar-Deficit model of reading, findings that warrant additional investigation.
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