DEVELOPMENT OF AN ADVANCED DIGITAL IMAGE-PROCESSOR FOR REAL-TIME SPECKLE SUPPRESSION IN ROUTINE ULTRASONIC-SCANNING

This paper describes a digital image processor for ultrasonic speckle suppression that was explicitly designed to satisfy the requirements o f detail preservation, adequate smoothing and real-time operation. The first two of these requirements were addressed by selecting a nonline ar adaptive algorithm, which uses a measure of local homogeneity to ad just the amount of smoothing performed at each point of the scan, and employing a large (9 x 9 pixels) filtering window. Real-time operation was achieved by developing a highly concurrent systolic architecture that allowed the efficient mapping of the algorithm into low-cost high -density hardware. Initial experience, obtained by interfacing the pro cessor to a scanner, suggests that this type of processing is capable of enhancing the visibility of subtle differences in echogenicity whil e retaining genuine image detail, as judged by the preservation of the small vessels and ducts. In addition to its impact on contrast resolu tion, this form of real-time speckle suppression should also prove val uable as a preprocessing stage before performing other digital image p rocessing operations that are sensitive to noise, such as segmentation and three-dimensional rendering.