Automatic Detection Of Rib Contours in Chest Radiographs

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 following are a few of the expected uses for the automatic detection of rib contours: 1. Rib images contribute false positives in tumor-detection algorithms. Hence> detecting the rib contours should f a c i l i t a t e removal of these lalse posltives . 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 accurate basis for computing the boundary of the chest cavity (referred to as the "lung boundary" In other papers) than other known techniques. Our algori thtn consists of a) high-pass f i l t e r i n g of the digitized picture, b) local "edge" detection by a combination of thresholding, Laplacian, and gradient operators, c) selection of edge elements in accordance w1th their angular orientation, d) matching straight line segments and conic sect ions to the selected edge elements, e) construct ing strips centered on the straight line segments and conic sections, and f ) heuristic search within these strips.