Methodological Study On Brain Structure Analysis Using Diffusion Tensor Imaging

Diffusion tensor imaging(DTI) is a recently developed functional magnetic resonance imaging(fMRI) technique in brain research.It is a new method to use the measurement of the anisotropic diffusion of water in organism to study the tissues of the human beings,specially showing the changes of micro-structures.So far,the technique is mainly applied in the brain research,particularly in the visualization and trajectory of white matter fiber bundles.In addition, the quantitative parameters,such as factional anisotropy,relative anisotropy and volume rate, can reveal the anisotropic characters of the brain tissues.Thus,DTI helps us deepen the understanding of the brain.This dissertation is mainly about the methodologies of DTI data analysis.The thesis primarily introduces the imaging elements of DTI technique and its correlated knowledge based on the elements of MRI.Then the anisotropic characteristics of the tissues in healthy subjects are studied and three types of fiber bundles are reconstructed successfully.The anisotropy research of a single subject shows the predominance of DTI in the study of individuals.In the patients with depression,the mean anisotropy in the whole brain and the fiber bundles in frontal lobe are changed.To our knowledge,most of the psychopathic researches have found the impairments in frontal lobe.For discussing the structural abnormities in herion-dependent subjects,a new method called quasi optimized voxel-based morphometry(quasi-OVBM) is described.This method inherits the simple operation flow and acute impersonal ability of differences examination,reserves more information and brings the research of white matter into prominence. Since the new method is validated in differences examination,the idea of the quasi-OVBM is used in normalizing the FA images.After that,a two-level asymmetry analysis method is applied to study the anisotropic asymmetry in herion-dependent subjects for the first time.Furthermore, adapting to the orientation of brain research,the integrated DTI/fMRI data are effectively used to study the structure-function impairments of early-onset schizophrenia.