| Summary: | 碩士 === 逢甲大學 === 自動控制工程所 === 96 === The purpose of this study is to evaluate the aging and small vessel disease (SVD) by diffusion tensor magnetic resonance image (DTI), including the parameters of apparent diffusion coefficient (ADC), fractional anisotropy (FA) and geometric diffusion indices (linear coefficient (CL), planar coefficient (CP), spherical coefficient (CS)). There are three subject groups in this study. One is young adults (< 50 years old), another is elder adults (>50years old), and the other is small vessel disease patients. All MR scans were performed by 1.5Tesla MR system (SIEMENS Vision). Trace apparent diffusion coefficient (tADC), fractional anisotropy (FA) and three geometric parameters (CL, CP, and CS) were derived from the three eigenvalues. Based on the knowledge of human brain anatomy on T2-weighted images and FA maps, the brain tissue was classified into six areas; i.e. genu, splenium, anterior periventricular white matter (right, left), and posterior periventricular white matter (right, left) under manual segmentation by a senior radiologist. Statistical analysis was performed with ANOVA and Student t-test for the comparison between the young adults, elder and SVD groups. Our results show significant age-related decline for FA and significant age-related increase for ADC in generally. Moreover, our results further reveal significant age-related decline in Cl and Cp and significant age-related increase in Cs in all regions. It discloses the facts that the aging process not only causes degeneration the white matter but also the gray matter and that the degeneration has shifted the geometric distribution of the brain tissue from linear and cylindrical to spherical shapes.
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