氫質子磁振頻譜 (Proton Magnetic Resonance Spectroscopy, Proton MRS)技術已經被普遍使用在腦部病變的診斷上。腦膿瘍 (abscess)的分類，一直是臨床上進行診斷與治療的重要步驟之一。近年來，由於磁振頻譜技術的非侵入性，以及在腦部偵測代謝物質的準確性，利用磁振頻譜技術幫助腦膿瘍分類診斷的重要性逐漸提昇。
由於腦膿瘍種類不同，在其磁振頻譜當中所觀察到的代謝物亦有所差異，根據這個特性，將磁振頻譜應用在腦膿瘍分類上，可以幫助提高診斷的準確性。然而，目前臨床上主要依據專業醫師針對不同迴訊時間之頻譜，判讀代謝物種類，進而進行分類。此方式很容易因主觀認定而產生診斷上之差異。所以在我們的研究中，主要利用主成分分析法（PCA），針對不同種類腦膿瘍病人的短迴訊磁振頻譜，進行較為客觀的分類。

Proton magnetic resonance spectroscopy has been widely applied to the diagnosis of brain diseases. In the meanwhile, the classification of brain abscesses plays an important role on the accurate prognosis in clinics. Recently, the interest in using
proton MRS to classify pyogenic brain abscesses has been arising because of its non-invasive property and good accuracy in detecting metabolites.
The brain abscess can be classified by means of the metabolites observed in the MR spectra, which may thus benefit the accuracy of the brain abscess diagnosis clinically.
However, the interpretation of MR spectra by experienced radiologists can be also very subjective and therefore results in the variation of diagnosis. In this study, we investigate the potential possibility of using Principal Component Analysis (PCA) to classify the short TE MR spectra in more objective way.

致謝................................................................................................................................ i
中文摘要........................................................................................................................ ii
Abstract ........................................................................................................................ iii
Table of Contents .......................................................................................................... iv
List of Figures ............................................................................................................... vi
List of Tables ............................................................................................................. viii
Chapter 1 Introduction ................................................................................................ 1
1.1 Background ...................................................................................................... 1
1.2 Literature Review............................................................................................. 4
1.3 Purpose ............................................................................................................. 7
1.4 Thesis organization .......................................................................................... 7
Chapter 2 Materials and Methods ............................................................................. 10
2.1 Acquisition techniques ................................................................................... 10
2.2 Eddy Currents Correction .............................................................................. 12
2.3 Principal Component Analysis ....................................................................... 12
2.4 Selection of Principal Components ................................................................ 15
2.5 Experiment design ......................................................................................... 16
2.5.1 Normal volunteers vs. Abscess patients ...................................................... 19
2.5.2 Classification within abscess patients ......................................................... 19
Chapter 3 Results and Discussions ........................................................................... 24
3.1 Discrimination between normal and patient subjects .................................... 24
3.2 Classification of various abscess patients ...................................................... 27
3.3 Comparison with clinical diagnosis ............................................................... 28
Chapter 4 Conclusion ................................................................................................... 55
References .................................................................................................................... 57

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