【摘要】 磁共振(Magnetic Resonance, MR)图像通常存在椒盐噪声(Salt and Pepper Noise, SPN)以及对比度低的问题,为了增强MR图像,分别在空域和频域针对不同侧重点分步进行滤波。对于多数滤波算法去除高水平SPN不理想的情况,提出了自适应加权重复值滤波算法(Adaptive Weighted Duplicate Filter, AWDF),通过连续放大窗口直到两个连续窗口的最大值和最小值分别相等来确定自适应窗口大小,用窗口内最大重复无噪像素的均值替代噪声像素。将其应用于不同噪声水平下的MR图像的预处理中,再在频域应用同态滤波。仿真结果表明,用自适应加权重复值滤波器和优化的高斯同态滤波器相结合的办法处理MR图像,能够在去除高水平SPN的同时提高图像对比度,增加图像细节,对图像的PSNR和SSIM等都有较大提高,图像增强效果显著。更多还原

【Abstract】 Magnetic resonance(MR) images are usually affected by salt and pepper noise(SPN) and low contrast.In this paper, we enhance the MR images by filtering the images in the spatial and frequency domain respectively.Since most of the existing filtering algorithms are not ideal for removing high-level SPN,we propose adaptive weighted duplicate filter(AWDF).The adaptive window size is determined by continuously enlarging the window until the maximum and minimum values of the two successive windows are equal respectively, and then replacing the noise pixel with the mean value of the most duplicate noise-free pixels in the window.We apply the algorithm to the pre-processing of MR images with different SPN levels, and then apply homomorphic filtering in the frequency domain.The simulation results show that the method of combining AWDF and optimized Gaussian homomorphic filter can improve the contrast and details of the images while removing high-level SPN.The PSNR and SSIM of the image have been greatly improved, and the enhancement is remarkable.更多还原