Concurrent smoothing and edge enhancement of medical diagnostic images

Abstract

A magnetic resonance imaging system (A) generates an image (16) of a slice or other region of an examined subject. A smoothing filter (B) smooths the generated image to create a smoothed or filtered image representation (30). The filtering of the image, unfortunately, tends to smooth or blur the edges. An edge detecting means (C.sub.1) views the region around each sampled pixel of the filtered image to determine an amount of deviation in the pixel values. A large deviation indicates an edge; whereas, substantial homogeneity indicates the lack of an edge. Analogously, the direction of the maximum deviation is orthogonal to the direction of the edge. A plurality of soft edge directional filters (54) operate on the filtered image data to create a plurality of soft edge directionally filtered image representations (62). A plurality of hard edge directional filters (56) operate on the filtered image data to create a plurality of hard edge directionally filtered image representations (64). Preferably, the directional filtering is done at regular angular increments, e.g. every ten degrees. An edge enhanced final image representation (72) is created in which filtered pixels not adjacent an edge are assembled directly from the filtered image (30). Pixels which are adjacent an edge with a smaller (larger) rate of deviation are replaced by the corresponding pixel of the soft (hard) edge filtered image representation that was directionally filtered along a direction most nearly parallel to the determined edge direction.