Penetration of Proton Beams through Water 2. Three-Dimensional Absorbed DoseDistributions

摘要

This report describes methods and computer programs for calculating absorbed-dosedistribution in a water target irradiated by proton beams. The spatial pattern of absorbed dose from monoenergetic pencil beams is calculated as a function of the depth in the target and of the radial distance from the pencil beam. This calculation uses the Monte Carlo program PTRAN and also Moliere's theory of radial multiple-scattering deflections. Such pencil-beam results are then combined linearly to obtain three-dimensional absorbed-dose distributions from beams that irradiate a field with arbitrary shape and size. In general, this requires a double numerical quadrature. Specialized formulas for circular and rectangular fields are also given which require only a single numerical quadrature.