中文摘要：

医学超声图像存在特有的斑点噪声，大大降低了图像质量，必须进行降噪处理。多小波具有比单小波分解更加精确、去噪效果更好的特点。对超声图像进行分形插值多小波分解，根据多小波分解后的能量分布特性，提出了改进多层闽值与模糊聚类相结合方法，将小波系数模糊聚类分成噪声和信号两类，然后在不同尺度对信号小波系数进行不同阈值萎缩处理，实现降噪目的。结果表明该方法优于硬阈值和软阈值法，可有效地降低图像斑点噪声并保留图像细节。

英文摘要：

There are inherent speckle noises in the medical ultrasound image.Image denoising is necessary for lower image quality.Multiwavelet has higher resolution and better denoising effect than scalar wavelet.Therefore,the modified multilevel threshold with fuzzy clustering is proposed based on the energy distribution of multiwavelet coefficients.First the ultrasound image is discomposed to multiwavelet domain.Then its coefficients are separated into noise and signal classes with fuzzy clustering.The signal coefficients are shrunk with different thresholds for image de-noising on the different scales.The result indicates the method is more effective than hard threshold and soft threshold.The speckle noise in the original image is removed efficiently and at the same time the image details are reserved.