磁共振頻譜是一種能夠觀察大腦內代謝物濃度的技術，然而所得到的頻譜品質往往受限於SNR過低或是頻譜的重疊。為了要提高SNR以及解決頻譜重疊的問題，提高主磁場環境以及使用MEGA選擇性脈衝是最好的方法，傳統3T環境下最常用來偵測具有J耦合特性代謝物的方法是MEGA-PRESS，但是在高磁場環境下PRESS序列會有化學位移偏移以及磁場不均勻的問題發生，因此使用其它空間定位方法，如semi-LASER序列加MEGA選擇性脈衝來偵測具有J耦合特性的代謝物。

乳酸(Lactate)是無氧代謝的最終產物，在正常人腦中大約只有0.5毫莫耳濃度，在大腦頻譜中缺氧、缺血性中風或是腫瘤的病患可以觀察到乳酸濃度有明顯的上升，因此乳酸被視為臨床診斷的重要指標。在這之前，高磁場環境中MEGA-sLASER序列只被用來偵測GABA而已，因此本文透過VeSPA模擬觀察高磁場(7T)下利用MEGA-sLASER偵測乳酸的可行性，並針對MEGA-sLASER序列中RF脈衝間的時間做調整及說明。

Magnetic resonance spectroscopy(MRS) is a technique to measure the concentration of metabolites in the brain. However, the quality of spectrum acquired from the magnetic resonance spectroscopy was always restricted by the low SNR or overlapping spectra. In order to increase the SNR and to resolve the overlapping metabolites, improving the magnetic field environment and using spectral editing techniques such as MEGA are the best way. MEGA-PRESS has been commonly used to detect the J-coupling metabolites at 3T, but PRESS sequence would cause chemical shift displacement and magnetic field inhomogeneous at higher field. Therefore, using other spatial localization techniques like semi-LASER combining with MEGA selective pulses is an alternative to detect J-coupling metabolites at higher fields.

There are only 0.5 mM lactate in human brain, which is the end product of anaerobic metabolism. In brain spectrum, we can observe that concentration of lactate dramatically raise on patients of cerebral hypoxia,ischemic stroke and tumors. Thus, lactate is considered as a key index in clinical diagnosis. Earlier, MEGA-sLASER has been only used to detect GABA at high field. Therefore, we investigate the usage of MEGA-sLASER to detect lactate at high field (7T) by VeSPA simulation. The designate timing between RF pulses of MEGA-sLASER for lactate editing is also proposed in this study.

目錄
第一章 簡介 1
1.1背景 1
1.2 文獻回顧 2
1.3研究動機 12
1.4組織架構 13
第二章 原理 14
2.1磁共振頻譜 14
2.2化學位移(chemical shift) 17
2.3化學位移偏移(chemical shift displacement) 19
2.4 J耦合特性(J-coupling) 21
2.5高磁場下的磁共振頻譜 23
2.6 乳酸(Lactate) 25
2.7 Adiabatic RF pulse 26
2.8 MEGA-sLASER 頻譜編輯 31
第三章 實驗方法設計與步驟 34
3.1 VESPA軟體介紹 34
3.2 MEGA-sLASER使用之參數 45
3.3 模擬時間參數設置 46
第四章 結果與討論 53
4.1 VeSPA模擬結果 53
4.2討論 54
第五章 結論 58
參考文獻 59
附錄 61

1. Preul MC, Caramanos Z, Collins DL, et al., Accurate non-invasive diagnosis of human brain tumors by using proton magnetic resonance spectroscopy. Nature Medicine, 1996. 2(3).
2. Mescher M, Merkle H, Kirsch J, et al., Simultaneous in vivo spectral editing and water suppression. NMR in Biomedicine, 1998. 11: p. 266-272.
3. Mullins PG, McGonigle DJ, O'Gorman RL, et al., Current practice in the use of MEGA-PRESS spectroscopy for the detection of GABA. Neuro image, 2014. 86: p. 43-52.
4. Graaf., R . A. De, In vivo NMR spectroscopy:principles and techniques. 2008: John Wiley&Sons.
5. Edden RA, Harris AD, Murphy K, et al., Edited MRS is sensitive to changes in lactate concentration during inspiratory hypoxia. Journal of Magnetic Resonance Imaging, 2010. 32(2): p. 320-325.
6. Pal D, Bhattacharyya A, Husain M, et al., In vivo proton MR spectroscopy evaluation of pyogenic brain abscesses: a report of 194 cases. Am J Neuroradiol, 2010. 31: p. 360-366.
7. Lange T, Ko CW, Lai PH, et al., Simultaneous detection of valine and lactate using MEGAPRESS editing in pyogenic brain abscess. NMR in Biomedicine, 2016. 29: p. 1739-1747.
8. Boer, V.O., Magnetic Resonance Spectroscopy at ultra-high field in humans. 2012: Utrecht University.
9. Balchandani P, Pauly J, and D., Spielman, Interleaved narrow-band PRESS sequence with adiabatic spatial-spectral refocusing pulses for 1H MRSI at 7T. MAGNETIC RESONANCE IN MEDICINE, 2008. 59(5): p. 973-979.
10. Scheenen TW, Klomp DW, Wijnen JP, et al., Short echo time 1H-MRSI of the human brain at 3T with minimal chemical shift displacement errors using adiabatic refocusing pulses. Magnetic resonance in medicine, 2007. 59(1): p. 1-6.
11. Andreychenko A, Boer VO, Arteaga de Castro CS, et al., Efficient spectral editing at 7 T: GABA detection with MEGA-sLASER. Magn Reson Med, 2012. 68(4): p. 1018-25.
12. Behar KL, Rothman DL, Spencer DD, et al., Analysis of macromolecule resonances in 1H NMR spectra of human brain. Magn Reson Med, 1994. 32(3): p. 294-302.
13. Henry PG, Dautry C, Hantraye P, et al., Brain GABA editing without macromolecule contamination. Magn Reson Med, 2001. 45(3): p. 517-520.
14. Buonocore MH and RJ., Maddock, Magnetic resonance spectroscopy of the brain: a review of physical principles and technical methods. Rev Neursoci, 2015. 26(6): p. 609-632.
15. Mekle R , Mlynárik V, Gambarota G, et al., MR spectroscopy of the human brain with enhanced signal intensity at ultrashort echo times on a clinical platform at 3T and 7T. Magnetic resonance in medicine, 2009. 61(6): p. 1279-1285.
16. Tannus A, Garwood M., Adiabatic pulses. NMR IN BIOMEDICINE, 1997. 10: p. 423-434.
17. Lai PH, Ho JT, Chen WL, et al., Brain abscess and necrotic brain tumor: discrimination with proton MR spectroscopy and diffusion-weighted imaging. American Journal of Neuroradiology, 2012. 23: p. 1369-1377.
18. Soher B.J., Semanchuk P, Young K, et al., Vespa-RFPulse User Manual and Reference.
19. Soher B.J., Semanchuk P, Young K, et al., Vespa-Simulation User Manual and Reference.
20. Soher B.J., Semanchuk P, Young K, et al., Vespa-Priorset User Manual and Reference.
21. Soher B.J., Semanchuk P, Young K, et al., Vespa-Analysis User Manual and Reference.