Neutron dose rate evaluation for medical linear accelerators

During X-ray therapeutic irradiation with energies above the threshold of (X,n) reactions in the structural materials of medical accelerators, a photoneutron fluence is generated. In Brazil, no measurements of neutron doses in radiotherapy rooms are being done yet, when licensing these equipment. Consequently, it is very important to obtain accurate analytical formulae and/or simulation of these dose rates, in order to estimate the increase in dose received by the patient and staff, as well as to correctly project the additional shielding for the treatment room. In this work, we present MCNP simulation of dosimetric quantities at the isocentre of some models of high-energy linear accelerators, and compare it with the values given by the manufacturers, finding good agreement between both.