A simple system for manual image reconstruction from pairs of X ray films

A simple mechanical back-projection system for X ray films is described which is easy to construct and implement. It enables mechanical simulation of the X ray geometry used when taking pairs of isocentric radiographs for reconstruction purposes. Such pairs may be conventional "AP and Lateral" sets but often it is preferable to take them in oblique directions on the order of 90 degrees apart. The device and the reconstruction method have proved to be very useful in determining target volumes for radiation treatment planning, especially if surgical clips and/or distinct anatomical structures are present. As an instructional tool it has advantages over an also locally developed computer-assisted method of reconstruction. The present system has proved to be highly useful especially in delineating the target volume for treatment planning of soft tissue sarcomas of the extremities and peripheral parts of the body, where detailed and accurate tailoring of shielding blocks is often of vital importance.