大腦半球表面的灰質組織稱為大腦皮質(Cerebral cortex)，近年的研究發現在部分中樞神經系統疾病的患者上皮質厚度有異常的現象，已知的疾病包括：多發性硬化症(Multiple sclerosis)、阿茲海默症(Alzheimer’s disease)、精神分裂症(Schizophrenia)等，因此使用非侵入性之磁共振影像進行大腦皮質厚度的量測也變得日益重要。本研究要實現一套前人所提出的體素式皮質厚度量測方法，進行全腦皮質厚度的自動化量測，並針對演算法中的細節進行討論，如：邊界條件定義方式、數值內插法、皮質路徑前進之單位距離(Step size)、和影像空間解析度。

此外，本研究也嘗試對自行開發的程式進行穩定性分析：研究方法是安排單一受試者在兩個月內重複十六次實驗獲得的T1權重影像，各自獨立完成皮質厚度的計算後，再經由對位，獲得皮質厚度在重複實驗中的平均、標準差、以及正規化標準差(Normalized standard deviation)分布圖。同時，也討論不同程度的平滑化(Smoothing)對於結果的影響。

The cerebral cortex is gray matter tissue which covers cerebral hemispheres. In recent years, many studies reported that abnormal cortical thickness was found in several diseases of central neural system, such as multiple sclerosis, Alzheimer's diseases, and schizophrenia. Therefore, the whole-brain measurement of cortical thickness using the non-invasive magnetic resonance imaging becomes important. However, not many algorithms were reported in the past due to the extremely complex folding structure of human cortex. In this thesis, a voxel-based cortical thickness method proposed by Hutton et al was implemented using MATLAB to achieve automated measurement. Several crucial factors, including the definition of boundary condition, interpolation method, the step size of developing each streamline, and spatial resolution of imaging space, in the implementation were discussed.

In addition, the analysis of stability, or precision, of our self-developed program was evaluated . Sixteen experiments of reproducibility were performed in two months on the same 24-year-old healthy volunteer repeatedly to obtain whole-brain 3D T1WI. Cortical thickness map was calculated independently and normalized to the same coordination. Mean, standard deviation, and normalized standard deviation of 16 measurements were calculated on every cortical voxel, along with whole-brain mean cortical thickness. Various sizes of 3D smoothing kernel were applied, and the results showed stronger smoothing might help higher precision by the cost of spatial resolution.

論文審定書...............................................................i
誌謝..........................................................................ii
中文摘要.................................................................iii
Abstract...................................................................iv
目錄.........................................................................v
圖目錄...................................................................vii
表目錄....................................................................ix
第一章 簡介..........................................................1
1-1. 背景.................................................................1
1-2. 研究動機.........................................................7
第二章 體素式皮質厚度量測研究方法..............8
2-1. 體素式皮質厚度量測.....................................8
2-1-1. 厚度定義的問題..........................................8
2-1-2. 量測之演算法..............................................8
2-2. 工作流程.......................................................11
2-2-1. 組織分割....................................................11
2-2-2. 標註腦溝體素............................................17
2-2-3. 皮質厚度量測............................................22
2-2-4. 影像模糊化................................................24
第三章 實驗設計................................................25
3-1. 自行開發程式之實現...................................25
3-2. 穩定性實驗設計...........................................26
第四章 實驗結果與討論....................................27
4-1. 不同邊界條件之比較...................................27
4-2. 不同解析度之比較.......................................32
4-3. 穩定性分析...................................................35
第五章 結論........................................................47
參考文獻..............................................................50

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