磁共振頻譜(magnetic resonance spectroscopy, MRS)可用來量化代謝物的濃度，並已經廣泛應用在臨床醫學上。但是一些臨床上應用的頻譜，其代謝物受到耦合系統的影響，使得頻譜產生重疊的現象，造成頻譜觀察及分析上的困難。為了改善此情況，我們以模擬的方式，觀察非對稱PRESS頻譜編輯區分強耦合代謝物的現象，並找出區分這些強耦合代謝物之最佳化實驗參數值。

非對稱PRESS頻譜編輯主要是利用改變PRESS間的重新聚焦脈衝時間來調配強耦合代謝物的訊號，透過頻譜相減消除單波峰及弱耦合代謝物的訊號，觀察出強耦合AB系統和MN系統的頻譜變化。我們的結果顯示，在一般常用的磁場下，此方法能有效取得強耦合代謝物頻譜，如glutamate、myo-inositol、NAA和taurine。而且，只需要改變TE1和TE2兩個參數，因此在實際臨床應用上也有其方便性的優點。

Magnetic Resonance Spectroscopy (MRS) has been used widely to quantify metabolite concentrations for clinical systems. However, some spectra in clinical application are obscured by stronger, overlapping resonances, and made the analytic and observation of these metabolites more difficult. In order to improve this situation, simulation was performed to generate spectra with PRESS asymmetry technique which helps to distinguish the strongly coupled metabolites. The experimental parameters were also optimized for these metabolites by this simulation.

PRESS asymmetry technique relies on strongly coupled signal modulation by changing the timing between refocusing pulses, and obtaining one spectrum of which singlets and weakly coupled signals were removed by subtraction. Then, it is possible to observe the signal variation of AB couple system and MN couple system. Our results show that, in conventional clinical field strengths, this method can extract spectra of some strongly coupled metabolites, such as glutamate, myo-inositol, NAA and taurine. Moreover, this technique is easy to be realized by changing TE1 and TE2 parameters, and is therefore convenient for clinical usage.

致謝 i
摘要 ii
Abstract iii
目錄 iv
圖目錄 v
第一章 緒論 1
1.1 概述 1
1.2 文獻回顧 1
1.3 研究動機 3
1.4 組織架構 4
第二章 原理 5
2.1 磁共振頻譜 5
2.2 人體大腦中常見的代謝物 7
2.3 化學位移 11
2.4 J-耦合 12
2.5 非對稱PRESS頻譜編輯 13
第三章 方法與步驟 15
3.1 VeSPA 15
3.2 數值模擬實驗設計 21
3.2.1 模擬參數設定 21
3.2.2 實驗步驟 21
第四章 結果 27
第五章 討論與結論 43
參考文獻 49

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