Abstract

An analytic expression for equivalent square fields and a table are derived using the empirical representations obtained from the measured field size dependence of output for square field in a phantom. The expression is applicable to radiation fields that consistent with the following two assumptions imposed on these representations. 1) It is a linear function of the logarithm of the field area. 2) It is approximately the same function for both square and circular field of similar areas. In this paper, the derived tables and BJR table were consulted.