COMPUTER GRAPHICS AND IMAGE PROCESSING 19,30 I(1 982)

Abstracts of Papers Accepted for Publication

PAPERS

Automatic Rib Detection in C/wst Rodiogrqhs. PETER DE SOUZA. IBM, UK Scientific Centre, St. Clement Street, Winchester SO23 9DR, England. Received February 3, 1982; revised April 22, 1982.

A detailed algorithm for automatic detection of posterior (dorsal) ribs in posterior/anterior chest radiographs is presented. It is entirely automatic and includes algorithms for locating the lung fields and the lung boundary. Written in PL/I for an IBM 3031, it requires about eight seconds to process a 400 X 400 digitized full chest radiograph which is significantly faster than previously published results. The reason for the efficiency can be attributed to the fact that no two-dimensional image processing is performed; it works instead by locating the ribs on a small set of one-dimensional sections taken through the lung fields. Curves are then fitted through these locations to represent the rib edges. The detection of anterior (ventral) ribs is also discussed.

RAYS-New Representation for Polygons and Pobhe&a. W. RANDOLPH FRANKLIN. Department of Electronics, Computer, and Systems Engineering, Rensselaer Polytechnic Institute, Troy, New York 12 18 I. Received April 23, 1982.

A new data structure for storing polygons and polyhedra is presented. It can handle fully general cases with multiple disconnected components and nested holes with islands to an arbitrary depth. The advantage of this method is that as in constructive solid geometry it can support Boolean operations such as union and intersection on nested hierarchical objects. Unlike CSG, however, properties such as area, perimeter, and moment of inertia can also be determined exactly. They can be determined by making one sequential pass through the object, which can be on secondary storage, calculating a scalar function of each ray, and adding the numbers. It is never necessary to determine either the global connectivity or the edges themselves. For polygons, the data structure is a set of semi-infinite rays where each ray also has an associated value, either “ + ” or “ - .” Each edge of the polygon is represented by two rays, although these two rays are nowhere tagged as belonging to the same edge, but are interspersed with all the other rays.

NOTES

4 New Connected Componenis Algorithm For Virtual Memory Computers. RONALD LUMIA, LINDA SHAPIRO, AND OSCAR ZUNIGA. Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061. Received April 5, 1982.

A new algorithm for calculating the connected components of a binary image is presented, and a proof of correctness is given. For a large image, this algorithm required one hour of CPU time while the standard technique used over 36 hours. The storage requirements for this new algorithm are appropriate for small minicomputers as well as for larger machines.

301 0 146-664X/82/07030 I-O I $0200/O

Copyright 0 1982 by Academic Press, Inc. All rights of reproduction in any form reserved.