SAR despeckling filters in ultrasound imaging

Ultrasonics is a widely used technique in medical imaging, due to its non-invasive nature and its capability of. forming real-time portraits of hidden targets. In this technique, pulse-echo ultrasonic waves are sent to the investigated medium and the backscattered waves provide the information for image formation. However, the coherent nature of the waves results in the appearance of speckle,noise. This phenomenon is common to laser, sonar and synthetic aperture radar (SAR) imagery, and is the result of interference between the scattered waves. Many filters have been proposed for alleviating this noise, especially in remote sensing applications. Some of these filters (Mean, Median, Lee, Frost and Gaussian MAP) are reviewed and applied to ultrasound B-scan images, along with a non-linear technique based on computing the median on the binary slices of the data. The performance of these techniques is assessed both quantitatively (regarding noise suppression and radiometric preservation) and qualitatively (through perceptual contrast and edge preservation).