An Analytical Model for Dosimetry of Nonstandard Photon Beams with Small, Round Cross Sections

Abstract

An analytical model of the dose kernel of a narrow photon beam (pencil beam) with a bremsstrahlung spectrum with maximal energy at 6 MeV was created, allowing determination of the primary and scattered components of the absorbed dose to be determined in a water phantom with error levels acceptable in practice. A simple method for the dosimetry of photon beams with small round cross sections with 6-MV bremsstrahlung spectra using this model is proposed, combining absolute measurement of the dose absorbed in the water at a reference point in the machine-specific reference geometry and calculation of the deep dose distribution using simple analytical equations for round beams with cross sections of any radius.