隨著核磁共振微成像技術的發展，目前空間解析度已逼近微米甚至亞微米。它在材料和生物體系中的研究起越來越重要的作用。為了研究獲取更精確的結構和動態數據，有必要進一步提高解析度。有兩個途徑達到此一目標。一是利用邊緣場的強梯度使相鄰像素的共振頻率差大於內部相互作用導致的譜線展寬。但此一方法往往只能在一個維度上實現高解析。因此第二個途徑，即通過消除固態或軟物質內部相互作用而達到高解析是更有普遍意義的方法。在固態核磁共振光譜學中，通常藉助於魔角旋轉(結合多脈衝去偶)來消除固態或軟物質樣品中和自旋之間相互作用的各向異性而使光譜的解析度大為提高。因此，魔角旋轉方法也可以應用於微成像而使影像有更好的解析度並節省成像時間。不過，將魔角旋轉用於微成像時，必須設法產生能跟蹤樣品旋轉的用於相位編碼和頻率編碼的梯度磁場。已有文獻報導的魔角旋轉微成像方法均採用特製的硬體來產生與魔角旋轉同步的交變梯度場。這種方法不但在技術上複雜，跟蹤效果也不夠理想。因此本研究開發了一個新的魔角旋轉微成像序列。本序列利用任意函數產生器結合梯度脈衝和梯度場放大器，產生一個數位控制的形狀化的梯度磁場來跟蹤樣品旋轉。此方法無需特製的硬體，可以在任何配有波型產生器的固態NMR譜儀上進行。脈衝序列中的同步觸發使得樣品轉速出現波動時亦可以保證梯度改變能跟蹤樣品旋轉。我們採用假體驗證了該方法的可行性。在高至1800 Hz的轉速範圍內可以實現較好的跟蹤而得到不錯的微影像。最後在固定大部份參數下(如轉速、厚度、np、 nv、nt=8、 FOV)，我們得到了初步的影像結果。

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第一章 緒論...............................................................................................................1
第二章 核磁共振原理簡介.....................................................................................4
2.1核磁共振的原理...................................................................................................4
2.2 RF(Radio Frequency)射頻場.................................................................................6
2.3 原子核自旋所形成磁矩與RF射頻場的關係..................................................7
2.4 T1以及T2的鬆弛過程............................................................................................8
2.5 T2*鬆弛................................................................................................................10
2.6 Bloch equation......................................................................................................11
第三章 磁共振成像基本原理...............................................................................13
3.1磁共振成像訊號形成的過程............................................................................13
3.2空間編碼(spatial encoding) .................................................................................13
3.3頻率編碼(frequency encoding) ...........................................................................14
3.4相位編碼(phase encoding) ..................................................................................15
3.5 k空間(k space) ....................................................................................................16
3.6截面選擇(slice selection) ....................................................................................17
3.7空間編碼的基本流程.........................................................................................17
3.8尤拉旋轉矩陣......................................................................................................18
3.9解析度...................................................................................................................20
第四章譜線寬化的來源..........................................................................................22
4.1固體中的自旋Hamiltonian..................................................................................23
4.2化學位移相互作用(chemical shift interaction) .................................................24
4.3偶極-偶極作用力(dipole- dipole interaction) ....................................................29
4.4四極作用力(quadrupole interaction) ..................................................................32
4.5魔角旋轉(magic angle spinning) ........................................................................35
4.6固體核磁共振成像方法...................................................................................36
4.7魔角旋轉成像......................................................................................................36
4.8魔角旋轉成像的原理.........................................................................................38
4.8.1實驗座標下的梯度......................................................................................38
4.8.2旋轉座標下的梯度......................................................................................31
第五章固體成像硬體簡介....................................................................................44
5.1射頻線圈............................................................................................................44
5.2梯度系統............................................................................................................45
5.3磁場.....................................................................................................................45
第六章 結果與討論..............................................................................................47
6.1 脈衝序列..........................................................................................................48
6.2 樣品...................................................................................................................48
6.3 討論...................................................................................................................49
參考文獻................................................................................................................67

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