Automatic Detection Of Rib Contours in Chest Radiographs

Abstract

We have constructed a computer algorithm that finds the contours of the dorsal and ventral portions of the images of ribs in chest radiographs. The fo llowing are a few of the expected uses for the automatic detection of rib contours: 1. Rib images contribute false positives in l·umor-Jetection algorithms. Hence, detecting the r I h co ntours should f ac il i. tate removal of these false positives. 2. The ribs provide a frame of reference for the description and location of lesions within the thoracic cavity. 3. The envelope of the ribs provides a more'accu r ate b as is for computing the boundary of the ch est cavity (referred to as the "lung boundary" in othe r papers) than other known techniques. Our algorithm consists of a) high-pass filtering of the digitized picture, b) local "edge" detection hy a combination of thresholding, Laplacian, and gradient operators, c) selection of edge elements in accordance with their angular orientation, d) matching straight l;ine segments and coni c sections to the selected edge elements, e) constructing strips centered on the straight line seg me nts and conic sections, and f) heuristic search within these strips.