关键词: 磁共振成像, 图像去噪, 小波变换, 提升格式, 自适应阈值

Abstract: This paper analyzes how the property of the wavelet effect the construction error of the image and then propose a improved method to increase the vanishing moment of a wavelet by lifting algorithm.By increasing the vanishing moment，the performance of traditional wavelet is improved to have the ability of capturing more details with a better vibration，and thus consequently enhances the reconstruction precision.according to the MR image characteristic and the noise distribution property，a more self-adaptive threshold selection method is proposed to thresholding wavelet coefficients.On each decomposition level，the coefficient matrix of the high frequency is deblocked to several sub-matrixes.The decomposition level，the contrast and the absolute median of a selected sub-matrix are combined to determine the threshold used to process the corresponding coefficients of the sub-matrix.So the thresholds determined by this method have a better self-adaptive performance.A large number of experiments on MR image are performed.The simulation results indicate that the denoising algorithm on MR image proposed in this article obtains a better performance，especially for MR image with lower signal-noise ratio.

Key words: MRI, image denoising, wavelet transform, lifting scheme, self-adaptive threshold