Empirical equations for Co-60 scatter-air ratio calculations

Simple empirical equations have been fitted to recognized tables of scatter-air ratio values for central points of square and circular fields of Cobalt-60 gamma rays with a maximum error of 0.006. From these equations further equations have been developed for scatter-air ratio calculations for off-axis points of rectangular fields and for corner points of triangular fields. The latter can be used in dose calculations for polygonal (irregular) fields. Herewith we have a complete system of equations for all practically important scatter dose calculations for Co-60 teletherapy.