Application of Three-Exponential Representation of Photon Buildup Factors to Water

The parameters for both Taylor and three-exponential representations of the point-isotropic-source dose buildup factors in water have been determined. The three-exponential representation is shown to provide a significantly better fit to the raw buildup factor data than either the Berger or the Taylor representation, while preserving the Taylor representation's most attractive feature, its amenability to integration over extended sources.