title: A study of neutron spectra from medical linear accelerators.
abstract: Medical accelerators with photon energies over 10 MeV generate an undesired fast neutron contamination in the therapeutic beam. In this work, the Monte Carlo code MCNP was used to simulate the transport of these photoneutrons across the head of various medical accelerators of high energy. The average and most probable neutron energies were obtained from these spectra, before and after crossing the accelerator shielding. The degradation of these spectra, when they cross concrete barriers with thickness which vary between 25 and 100 cm, was also studied.
authors.affiliation: Comissão Nacional de Energia Nuclear, R. Gal. Severiano 90, sala 405, 22294-900, Rio de Janeiro, RJ, Brazil.
authors.forename: A
authors.initials: A
authors.lastname: Facure
authors.forename: R C
authors.initials: RC
authors.lastname: Falcão
authors.forename: A X
authors.initials: AX
authors.lastname: Silva
authors.forename: V R
authors.initials: VR
authors.lastname: Crispim
authors.forename: J C
authors.initials: JC
authors.lastname: Vitorelli
mesh_terms: D016477:Artifacts; D003198:Computer Simulation; D019544:Equipment Failure Analysis / Q000379:methods*; D005214:Fast Neutrons; D015233:Models, Statistical; D009010:Monte Carlo Method; D011829:Radiation Dosage; D011835:Radiation Protection / Q000379:methods; D011874:Radiometry / Q000379:methods*; D016634:Radiosurgery / Q000295:instrumentation*; D015203:Reproducibility of Results; D018570:Risk Assessment / Q000379:methods*; D012307:Risk Factors; D012680:Sensitivity and Specificity