北京生物醫(yī)學(xué)工程

微波熱療凝固區(qū)域超聲回波信號的小波去噪方法

Wavelet denoising method for ultrasonic echo signal in microwave hyperthermia coagulation zone

作者：劉振臨楊春蘭盛磊吳水才

單位：           北京工業(yè)大學(xué)生命學(xué)院生物醫(yī)學(xué)工程中心（北京 100124）    

關(guān)鍵詞：超聲檢測；局部分層閾值；小波變換；閾值去噪

分類號：

出版年·卷·期（頁碼）：2012·31·1（31-35）

摘要：

目的針對用于監(jiān)測微波熱療凝固區(qū)域的超聲回波信號信噪比較低，強反射點較多，難以定位凝固區(qū)域邊緣的特點，研究了一種基于小波分解的去噪方法。方法在理論分析的基礎(chǔ)上，對超聲回波信號進行小波分解，根據(jù)不同頻段信號的特征，進行局部分層小波閾值去噪，再通過小波重構(gòu)得到去噪后的超聲回波信號。結(jié)果對比硬閾值去噪、軟閾值去噪和本文所采用方法的效果，探討了利用本文算法進行凝固區(qū)域邊緣識別的可行性。結(jié)論局部分層小波去噪算法可有效抑制噪聲，保留信號的細節(jié)特征，達到優(yōu)化超聲回波信號的目的。

Objective In the monitoring process of the microwave hyperthermia，the ultrasonic echo signals were acquired with low signal noise ratio(SNR)，a large number of strong reflection points，indistinct edges of coagulation zones. A denoising method based on the wavelet decomposition was studied in this paper. Methods Based on the theoretical research，an ultrasonic echo signal was decomposed into different frequency bands through wavelet transformation. According to the characteristics of these frequency bands，the signal was denoised by local multi-level threshold method and the denoised signal was obtained by wavelet reconstruction. Results The denoising effects of hard threshold，soft threshold and local multi-level threshold respectively were compared based on the experimental data. The feasibility of using this method to identify the edge of the coagulation zone was also investigated. Conclusions The experimental results showed that the local multi-level threshold method could depress noises effectively and retain the detailed characteristics to optimize the ultrasonic echo signals.

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