結合階梯平滑化法與小波變換強化胃部超音波影像

Gastric Sonogram Image Enhancement by Histogram Equalization and Wavelet Transforms

傅家啟(Jachih J. C. Fu) ； 連漢仲(Han-Chung Lien) ； 王天賜(Stephen T. C. Wong) ； 張世穎(Shi-Yin Chang)

《大葉學報》 8卷1期 (1999/06) Pp. 69-78

https://doi.org/10.7119/JDYU.199906.0069

摘要

胃部超音波掃瞄影像像素之灰階值常因集中於一端而導致影像過黑之現象，此現象雖可經階梯平滑化法藉重新分配灰階值趨向於均勻分配而改善，惟階梯平滑化法於演算過程中會減少影像之資訊量，本論文於階梯平滑化法之後加裝一小波變換演算法，以增加資訊量並同時強化影像。實驗結果顯示，小波變換法處理後之影像資訊量熵值顯著增加；並經由專業醫師判讀結果顯示，小波變換為基礎之演算法可有效強化胃竇輪廓。因此結合階梯平滑化法與小波變換演算法可同時強化胃部超音波影像之對比度及增加影像資訊量，以提高醫療診斷及研究之品質。

關鍵字

影像強化 ； 小波變換 ； 資訊量熵值

並列摘要

The gray levels of gastric sonogram images are usually concentrated at the zero end of the spectrum, making the image too dark for the naked eye. Though histogram equalization can enhance the contrast by redistributing the gray levels, it has the drawback that it reduces the information in the processed image. In this paper, a wavelet based enhancement algorithm postprocessor is used to further enhance the image and compensate for the information loss during histogram equalization. Experimental results show that the wavelet based enhancement algorithm can enhance the contrast and significantly increase the informational entropy of the image. Because the combination of the histogram equalization and wavelet approach can dramatically increase the contrast and maintain information rate in gastric sonograms, it has potential as a helpful tool in clinical diagnosis and research.

並列關鍵字

image enhancement ； wavelet transform ； entropy