Real-time implementation of coherent speckle suppression in B-scan images

Early experiences of new forms of adaptive filtering for ultrasound speckle reduction and parametric imaging, using off-line conventional digital processing, have been sufficiently encouraging to warrant examining the feasibility of implementing specific algorithms in real-time. A hardware two-dimensional real-time filter is described which consists of a hybrid digital/analogues system in which the video signal from any scanner is sampled to 256 points per line and passed sequentially through a series of shift registers, in order to derive a 5 x 5 window of values which surrounds the image point currently being processed. These 25 video signals are then used as inputs to an analogue processor, which provides the filtered output. The real-time processed images show clear evidence of speckle smoothing without blurring of tissue structural information but possess limited pixel resolution.