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Please use this identifier to cite or link to this item: http://ntour.ntou.edu.tw:8080/ir/handle/987654321/18463

Title: 可變動區塊小波轉換醫學影像編碼
Variable Block size Wavelet-Transform Medical Image Coding
Authors: Jhih-Wei Jian
Contributors: NTOU:Department of Communications Navigation and Control Engineering
Keywords: 小波轉換;四分樹;向量量化
Quadtree Segmentation;Wavelet Transform
Date: 2010
Issue Date: 2011-07-04
Abstract: 本論文首要是對醫學影像利用小波來壓縮編碼進行研究,並且是假設在傳輸通道無雜訊及無誤差條件下,應用於醫學影像的壓縮上。為了要增加在影像的壓縮比率,所以將小波轉換後的小波係數經過向量量化後再來進行壓縮,因為使用向量量化的主要原因是由於它具有很高的壓縮比率,所以在解壓縮時也相當容易。在研究裏提出用四分樹分割法作為在影像的前處理,把影像的細節和背景部份分割成尺寸大小不同的區塊,再經小波轉換後將每一個子頻帶區塊的小波係數能量值(variance),來做為位元分配的依據。由分配到的位元選擇最適當的編碼簿(codebook),並且編碼後得到的失真值來調整位元率,因為切割影像區塊的像素差異性較低,所以可增快向量量化編碼的速度進而改善影像壓縮之效能。 關鍵字:小波轉換、四分樹、向量量化。
Wavelet transform technique is widely used in image compression because it provides a multiresolution representation of images. With vector quantization algorithm, the wavelet transformed coefficients can be compressed further. In this study, we have proposed a quadtree segmentation method for medical image preprocess. Quadtree segmentation algorithm is used to divide a given MRI medical image, where regions with image detail will be segmented into blocks with smaller block size, and the background of the image will be assigned larger block size. Choosing proper size of vector quantized codebook after the wavelet transform, we have applied bit allocation assignment associated with the variance of each sub band image block. For this proposed medical image compression scheme, simulation results show acceptable visual quality and good compression ratio simultaneously. Furthermore, due to the codebook size been reduced, we are able to save the computational time. System performance analysis is also demonstrated in this thesis. Key Words : Quadtree Segmentation, Wavelet Transform
URI: http://ethesys.lib.ntou.edu.tw/cdrfb3/record/#G0M96670041
Appears in Collections:[通訊與導航工程學系] 博碩士論文

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