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Please use this identifier to cite or link to this item: http://ntour.ntou.edu.tw:8080/ir/handle/987654321/35749

Title: 降低加乘性雜訊的混雜濾波方法
A Heterogeneous Filtering Method for Multiplicative Noise
Authors: Guan-Zhi Chen
Contributors: NTOU:Department of Computer Science and Engineering
Keywords: 超音波醫學影像;加乘性雜訊;混雜濾波
Ultrasound Medical Image;Multiplicative Noise;Heterogeneous Filtering Method
Date: 2012
Issue Date: 2013-10-07T02:58:42Z
Abstract: 超音波影像容易產生亮斑雜訊,導致組織輪廓變得模糊,影響影像的品質,因此抑制亮斑雜訊在超音波影像的視覺化中是非常重要的。線性濾波器可以抑制亮斑雜訊,但是也會造成影像的模糊化。使用中間值濾波器可以獲得較好的結果,然而中間值濾波器會在灰階值不均勻的區域產生人為圖樣,影響觀察者的判斷。我們會在本論文中提出一種嶄新的超音波去雜訊演算法。在本方法中,我們會在每一個像素算出灰階值的擴散矩陣。然後利用擴散矩陣的特徵值及特徵向量進行結構分類。最後利用結構的種類選擇合適的濾波器在該像素進行雜訊抑制及特徵加強。測試結果顯示出本方法能夠有效改善超音波影像的品質,我們的方法對亮斑雜訊和一般加乘性雜訊有良好的抑制效果,並且能夠加強組織特徵。
Ultrasound images are prone to speckle noise. Speckles blur key features which are essential for diagnosis and assessment. Thus despeckling is important in ultrasound data visualization. Linear filters suppress speckles, but they also smooth out key features. Median filter based despeckling algorithms can produce better results. However, they may produce artifact patterns in the resulted images and over-smooth non-uniform regions. In this thesis, we presents an innovative despeckle algorithm for ultrasound images. The diffusion tensor of intensity is computed firstly at each pixel in our proposed method. Then the eigen system of the diffusion tensor is calculated and employed to detect and classify the underlying structure. After finishing above mentioned steps, the computed structure type is utilized to select a feasible filter to suppress speckles and enhance the detecting feature. The test results show that the proposed despeckle method reduce speckles and enhance tissue boundaries for ultrasound data. In another test, the proposed despeckle method is employed to remove multiplicative noise for grey level images. The experimental results show that our method is also effective for reducing multiplicative noise and enhancing features for grey level images.
URI: http://ethesys.lib.ntou.edu.tw/cdrfb3/record/#G0010057020
Appears in Collections:[資訊工程學系] 博碩士論文

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