研究生: |
林傳晉 |
---|---|
論文名稱: |
奇異值分解法用於心磁圖雜訊消除之研究 |
指導教授: |
楊鴻昌
Yang, Hong-Chang 洪姮娥 Horng, Herng-Er |
學位類別: |
碩士 Master |
系所名稱: |
光電工程研究所 Graduate Institute of Electro-Optical Engineering |
論文出版年: | 2005 |
畢業學年度: | 93 |
語文別: | 中文 |
論文頁數: | 42 |
中文關鍵詞: | rf-SQUID 、奇異值分解法 、心磁圖 |
論文種類: | 學術論文 |
相關次數: | 點閱:231 下載:0 |
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我們使用一階高溫超導rf-SQUID梯度計在磁屏蔽屋裡測量生物的心磁訊號,一階梯度計是由兩個高溫rf-SQUID所組成,待測者有人體與兔子,人體分別為健康者與心律不整者,兔子分別為健康兔子與高血脂兔子。
以往實驗室對於心磁數據處理方式只有透過平均處理來降低雜,提高訊雜比,但若要處理心律不整者的心磁信號時,由於心磁信號週期長短不一,平均處理後有可能會使原本的信號失真變形,使判讀時失去心磁訊號的正確性。因此,量測心律不整者時,必須不必透過平均處理,最好能夠直接讀取及時的心磁信號,在一般情況下,及時所量得的信號裡所包含的雜訊,會使得信號與雜訊分辦不清,難以從及時的心磁圖中判別病症,因此我們才利用奇異值分解法(Singular Value decomposition, SVD)來消除及時信號中的雜訊。
由於心磁訊號有類似週期特性,奇異值分解法是將訊號分成單位向量與相對大小權重之線性組合,可將心磁信號中重要的生理特徵從原始波形中解離出來,將其他殘餘的背景雜訊以及微小訊號的分量去除,進而能消除雜訊,改善訊雜比。
人體與兔子的心磁信號經過奇異值分解法處理後,訊雜比分別可提高四倍與兩倍。但經過奇異值分解法再經平均處理的心磁圖,與未經過奇異值分解法處理直接平均處理後的心磁圖相比,並無明顯的差異,從平均結果比較後的結論是若想要得到平均後的心磁圖,可以不須經過奇異值分解法而直接作平均處理;若想要得到及時的心磁圖,便可以利用奇異值分解法作處理。
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