in ultrasound imaging , acquired images are corrupted by slowly varying multiplicative non - uniformity . when the image is corrected for non - uniformity alone , noise in the dark regions of the original image becomes multiplicatively enhanced , thereby providing an unnatural look to the image . a pre - filtering technique is used to reduce noise in ultrasound pixel images by shrinking initial image data and processing the shrunken image with known segmentation - based filtering techniques that identify and differentially process structures within the image . the segmentation is based on both gradient threshold and the distance from the near field of the ultrasound image . this modification selectively suppresses near - field artifacts . after processing , the shrunken image is enlarged to the dimensions of the initial data and then blended with the initial image to form the final image . during blending , a small predetermined fraction of intensity - dependent , uniform random noise is added to the non - structure region pixels whose intensities are above a pre - specified intensity threshold , to mitigate ultrasound speckles while leaving non - echogenic regions undisturbed .