為了降低手動分割多發性硬化症的病變所造成的問題，如耗時、評估者之間的差異，所以越來越多人提出多發性硬化症的病變的自動分割法。本論文針對多發性硬化症的白質病變進行自動分割，使用了三種不同的磁振造影序列(T1-w, T2-w, FLAIR 影像)。我們主要使用高斯混合模型來評估正常組織的高斯分佈的參數，其中會先評估出可能是離群值的部分並扣除掉，再評估出正常組織的參數，由於多發性硬化症的白質病變在T2-w 和FLAIR 影像中屬於高強度，所以將評估出來的離群值對應到這兩種影像上來找到高強度的地方，也就是多發性硬化症白質病變的位置，最後執行後處裡，將偽陽性排除。將最後得到的病變計算出體積，可以幫助醫師長期監督病變的變化。

Manual lesion segmentation of Multiple Sclerosis (MS) lesions is time consuming and has an intra- and interrater variability. To resolve these issues, there are several auto-segmentation methods. This thesis implements an automatic MS lesion segmentation method targeting white matter lesions (WML), uses three different MRI sequences (T1-w, T2-w, FLAIR image) as the input of our algorithm. We use Gaussian Mixture Model (GMM) to estimate the parameters of Gaussian distribution of NABT (normal appearing brain tissue) and we will remove the outlier candidate data during this process to ensure correctness. MS WML has hyper-intensity on T2-w and FLAIR images, so we find the hyper-intensity pixels on these two kinds of images using the outlier information estimate from the previous step. In the post-processing, we remove false positive using rule-based methods and evaluate the volumes of lesions to help doctors supervise the progress of lesion in long term.

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