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| 研究生： |
陳伯勛 Po-Hsun Chen |
|---|---|
| 論文名稱： |
利用自我相位影像估計法移除平面回訊影像假影 Removal of Echo Planar Imaging Nyquist Ghost With Self Phase Image Estimation Method |
| 指導教授： |
林益如
Yi-ru Lin |
| 口試委員: |
阮春榮
Chun-Jung Juan 黃騰毅 Teng-Yi Huang 蔡尚岳 Shang-Yueh Tsai |
| 學位類別： |
碩士 Master |
| 系所名稱： |
電資學院 - 電子工程系 Department of Electronic and Computer Engineering |
| 論文出版年： | 2009 |
| 畢業學年度： | 97 |
| 語文別： | 英文 |
| 論文頁數： | 58 |
| 中文關鍵詞： | 平面回訊影像 |
| 外文關鍵詞： | Nyquist ghost, echo-planar imaging, ghost reduction |
| 相關次數： | 點閱：208 下載：1 |
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本論文展示一種平面回訊影像中的奈圭斯特假影修正方法。奈圭斯特假影主要是因為K空間中單數及雙數資料中有各自的相位誤差存在，影像中會在相位編碼方向產生假影，而且假影與原始影像的距離是視野範圍的一半；修正方法是先分別取得K空間中單數及雙數的資料，做二維反傅立葉轉換得到各自的相位影像，再對相位影像中間未被假影重疊的部份做零次方與一次方的線性估算，將得到的結果對影像相位做修正，讓相位誤差都趨近於零，將影像結合得到最後結果。
另外將此方法與 Homodyne 方法做連結，將不完整的平面回訊原始資料經過相位修正移除奈圭斯特假影後，再做半傅立葉的影像處理，修正模糊現象，得到最後結果。
Nyquist ghost is a well known problem in echo planar images (EPI), which manifests itself as an aliasing ghost displaced at FOV/2 apart from the object along the phase encoding direction and a consequent decrease in the object signal intensity. One common method to correct for the problem is to perform a reference scan without blip phase gradient, with odd and even phases corrected using the reference data. A disadvantage of this method is the temporal deviation between reference scan and image scan, causing phase estimation error in the presence of motion. In this work, we proposed a simple alternative method which corrected the Nyquist ghost without reference scan. The method based on the estimation of phase profile from image itself, and correct the phase in image domain to remove the ghost and recover the signal of object.
Combine the proposed method with Homodyne method in half Fourier image to correct Nyquist and blurring artifact, results demonstrate the combination is workable and may provide benefit in further application.
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