Monte Carlo simulation and experimental evaluation of photoneutron spectra produced in medical linear accelerators

Linear accelerators for the cancer radiotherapy generally make use of high-energy photon beam. If the photon energy is greater than 6-7 MeV, neutrons are generated by a photonuclear reaction in the accelerator head. The neutron spectrum and yield at the patient plane must be known in order to optimize the treatment and limit secondary malignancies. The spectrum of neutrons generated by the (/spl gamma/,n) reaction in the SL20I ELEKTA multileaf accelerator has been obtained at the patient plane with a Monte Carlo simulation. The calculated spectrum has been checked out against experimental measurements performed, in different positions at the patient plane, with a passive bubble spectrometer.