中文摘要：

针对小波去斑方法在医学超声图像抑斑上的不足，提出一种混合离散小波变换DWT（Discrete Wavelet Transform）和双树复小波变换DTCWT（Dual-tree Complex Wavelet Transform）进行阈值处理和变量收缩的医学超声图像自适应去斑算法。首先，在小波域，根据小波系数能量的特点，计算综合阈值实现图像预处理；然后，结合小波系数的尺度相关性，提出一种改进的三变量收缩函数，实现图像去斑。实验结果表明该方法较已有的经典方法更为有效，一般情况信噪比可提高0.6-2.6dB，图像边缘信息保持能力更突出。

英文摘要：

Aiming at the shortage of traditional wavelet-based despeckling methods for medical ultrasound images, we present a novel adaptive despeckling algorithm for medical ultrasound image, which applies the hybrid discrete wavelet transform （DWT） and dual-tree complex wavelet transform （DTCWT） in threshold processing and variable shrinking. First, the synthesis threshold in wavelet domain is calculated according to the feature of wavelet coefficients energy to realise image preprocessing; Then, an improved trivariate shrinkage function is presented in combination with the scale correlation of wavelet coefficients to implement image despeckling. Experimental results demonstrate that our method is more effective than the existing classic methods, which can raise the signal-to-noise ratio （SNR） by 0.6~2.6 dB with better performance of edge preservation in general circumstance.