Ultrasound Image Denoising Using Wavelet Thresholding Methods in Association with the Bilateral Filter

Ultrasound imaging has been widely used in medical diagnosis in modern medicine. Although widespread, it presents low-resolution images, typically degraded by speckle noise, which requires the use of image-processing techniques aiming at improving the image quality and allowing a proper medical diagnosis use. This paper presents a new association based on S-median thresholding and the fast bilateral filter for speckle noise reduction. In order to validate the results, the proposed method was analyzed and compared with two others thresholding methods. The image quality improvement is evidenced by an increase of 14.13% in PSNR while the structural features and contour preservation have increased 4.96% in MSSIM and 0.70% in beta, respectively. As the obtained results shown, the proposed method is able to reduce the speckle noise, to preserve the spatial characteristics and the contour information of the images and it is indicated for noise reduction at noise levels commonly found in ultrasound equipment.