Determination of Small Beam Axial Dose Distribution in Water Based on the Mathematical Model of Pencil Beam Kernels

Abstract

An analytical model of the dose kernel of pencil beam for photon with the Bremsstrahlung spectrum with maximum energy 6 MV was created in this work, which makes it possible to determine the primary and scattered components of the absorbed dose in water phantom with an acceptable error for practice. Using this model a simply method of dosimetry of small circular cross section 6 MV photon beam was proposed. It combines the absolute measurement of the absorbed dose in the water at the reference point for reference geometry with the calculation of the deep dose distribution by simple analytical formulas for circular beams with an arbitrary radius of the cross section.