Evaluation of in-field neutron production for medical LINACs with and without flattening filter for various beam parameters - Experiment and Monte Carlo simulation

Abstract A comprehensive study on the evaluation of in-field photo-neutron and electro-neutron dose equivalent (H ∗ (10)), neutron fluence and energy spectra was carried out using passive detectors such as PADC and TLDs and supplemented with Monte Carlo simulation. The studies were carried out for VARIAN LINAC models NovalisTx and TrueBeam. Measurements on the influence of beam parameters such as field size, wedge angle, depth in phantom, photon and electron energies and variation of neutron dose equivalent with distance from isocentre were studied. Further, influence of beam flattening filter for 10 MV photon beam in TrueBeam was included. Simulation using FLUKA Monte Carlo code for the generation of neutron lethargy spectra and spectra weighted H*(10) at different depths of phantom was performed. Influence of different components of LINAC head on neutron spectra was also simulated for 15 MV photon beam with and without flattening filter.