A CLARKSONS SECTOR INTEGRATION ROUTINE FOR PERSONAL COMPUTERS

A Clarkson's sector integration scheme has been implemented on a perso nal computer to calculate mean scatter-air ratio ((SAR) over bar) and mean tissue-air ratio ((TAR) over bar) for external photon beams of ir regular shape. To find where a given radial line from the point of int erest intersects the edge of the radiation field, polygon clipping alg orithms have been adapted from the field of image processing. The prog ram has calculation run times of similar to 1 s on an 80387 with a mat h coprocessor for an integration of 36 sectors. The software was valid ated by comparison to program IRREG, where for various squares and cli nical shapes, the agreement was typically 0.7%. The source code is ava ilable from the authors.