特徵自我選取方法運用於多頻譜MRI影像之分類

A Feature Selection Method Application on Multi-spectral MR Images Classification

林耿呈(Geng-Cheng Lin)

指導教授 ： 王文俊

國立中央大學/資訊電機學院/電機工程學系/碩士(2007年)

摘要

核磁共振技術(Magnetic Resonance Imaging, MRI)為現今臨床上重要的檢測技術，其核磁共振技術最大優點是對人體不具侵襲性，且可以多方向掃描，並提供三度空間、高對比度的影像。可有利於醫師對疾病的診斷更加準確，以提高治療的正面效果。當一病人被安排做MRI造影後，對人體某一器官切面部位，會產生一系列的多頻譜影像(multi-spectral image)。如果把一系列的切面影像疊在一起組合而成後，便形成人體一個立體的三維結構。醫師就藉由這個立體結構得到一些醫學診斷的資訊，如器官的形狀、位置與體積大小。雖然經由多頻譜影像可獲得更多的資訊，但也造成病理判讀上的困擾。因此，我們將這些多頻譜影像經過精準的轉換法處理後，形成單一強化組織影像讓醫生更容易的對病理做診斷。
此篇論文提出了一個新特徵自我選取的方法，Target generation process(TGP)。並將TGP合併於Linear Discriminant Analysis (LDA) 與 Support Vector Machine (SVM)兩方法。我們稱此兩方法為Unsupervised Linear Discriminant Analysis (ULDA) 與 Unsupervised Support Vector Machine (USVM)。利用ULDA(或USVM)來強化出腦中的CSF(cerebrospinal fluid),白質(White Matter)以及灰質(Gray Matter)三大組織，使醫生做診斷時更加有效率。因此我們的工作即在研究如何從多頻譜MRI影像中，將腦部的主要組織(如CSF、WM、GM)給強化出來，且亦有一套方法來評比這些方法的可行性與強健性。

關鍵字

分類 ； 特徵自我選取 ； 多頻譜影像 ； 核磁共振

並列摘要

Magnetic Resonance Imaging (MRI) is a useful medical instrument in medical science. It provides unparallel capability of revealing soft tissue characterization as well as 3-D visualization and proposes the diagnosis without needing to intrude into the human body. MRI produces a sequence of multiple spectral images of tissues with a variety of contrasts, but the multi-spectral images cannot be conveniently used to be a pathology diagnosis correctly. In general, we need to transform the multi-spectral images to an enhanced image which is easier to be used for doctor’s clinical diagnosis. One of the potential applications of MRI in clinical practice is the brain parenchyma classification.
In this thesis, we first present a feature selection method called Target Generation Process (TGP) and the TGP generates a set of potential targets from an unknown background. Let the targets be the training data for the classifiers of Linear Discriminant Analysis (LDA) and Support Vector Machine (SVM), respectively, such that the classification and segmentation for the MR images are achieved. The algorithm combining TGP and LDA (or SVM) is called Unsupervised Linear Discriminant Analysis (ULDA) (or Unsupervised Support Vector Machine (USVM)). Finally, the effectiveness of ULDA and USVM in target classification is evaluated by several MRI images experiments. In order to further evaluate its performance, they are compared with the method of Fuzzy c-mean. Several experiment results show that the ULDA and USVM have the better effective segmentation for multi-spectral MR images.

並列關鍵字

feature selection ； classification ； unsupervised ； Magnetic Resonance Imaging (MRI)

參考文獻

[1] C. M. Wang, et al., “An Unsupervised Orthogonal Subspace Projection Approach to MR Image Classification," Optical Engineering, vol. 41, no. 7, pp. 1546-1557, July. 2002

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[4] C. M. Wang, et al., “An Unsupervised Kalman Filter-based Linear Mixing Approach to MRI Classification,” Proceedings of the 2004 IEEE Asia-Pacific Conference on Circuits and Systems, vol.2, pp.1105 – 1108, 6-9 December 2004.

[5] W. E.Reddick, et al., "Automated Segmentation and Classification of Multispectral Magnetic Rresonance Images of Brain using Artificial Neural Networks," IEEE Transactions on Medical Imaging, vol. 16, no. 6, pp. 911-918, December 1997.