Split Phase Processing — a Single Image, Resolution Loss Free Method for Ultrasound Speckle Reduction

B-mode ultrasound images are characterised by the speckle artefact, which results from interference effects between returning echoes, and may make the interpretation of images difficult (Burckhardt, 1978). Consequently, many methods have been developed to reduce this problematic feature, some requiring many images, while others require only a single image as input. Two widely used methods, for both medical and non-destructive testing applications, are: a) split spectrum processing (SSP), also known as frequency diversity (a single image technique); and b) angular compounding (a multi image method). SSP is traditionally performed in 1D, where each single individual RF A-line is filtered by a set of relatively narrow band pass filters and the outputs are compounded to generate a speckle-reduced envelope that exhibits a significant resolution loss (Shankar and Newhouse, 1985). On the other hand, the angular compounding method does not suffer from this problem, but requires that the analysed structure be imaged from a large number of different directions - a severe practical limitation for medical imaging.