The storage and manipulation of radiation dose data in a small digital computer

A small dedicated computer has been in routine use for three years for the production of dose distributions for 1,000 patients per year. It has completely replaced hand drawing procedures. Details are given of the physical and computing principles employed in the system. A method of beam tabulation designed to minimize the amount of data stored in the computer and suitable for a wide variety of beams, is described. This method has been found to give accurate results in all parts of filtered or unfiltered beams produced by cobalt 60 and by 6 MeV and 8 MeV linear accelerators. A correction procedure is used which makes accurate compensation for skin curvature and for variations in SSD, which occur in isocentric treatments. The method has been further developed to compensate for tissue inhomogeneities, such as bone and lung, with little reduction in speed of calculation. Finally, methods are described which have been used to obtain beam data in the right form for storage and subsequent retrieval.