Speckle reducing anisotropic diffusion for 3D ultrasound images

This paper presents an approach for reducing speckle in three dimensional (3D) ultrasound images. A 2D speckle reduction technique, speckle reducing anisotropic diffusion (SRAD), is explored and extended to 3D. 3D SRAD is advantageous in that, like 2D SRAD, it keeps the advantages of the conventional anisotropic diffusion and the traditional speckle reducing filter, the Lee filter, by exploiting the instantaneous coefficient of variation (ICOV). Besides, 3D SRAD uses 3D information; thus it overcomes the shortcoming of the 2D technique that only uses 2D information. The algorithm of 3D SRAD is presented in the continuous domain as well as in the discrete domain. Experiments have been performed on both synthetic and real 3D ultrasound images and the experimental results were compared with those obtained by 3D anisotropic diffusion and the 3D Lee filter. The experimental results show that the quality of the 3D SRAD for speckle reduction in 3D ultrasound images improves upon that of 3D anisotropic diffusion and 3D Lee filter in terms of edge preservation and the smoothness of homogenous regions.