Analysis of personnel exposures in neutron therapy facilities

In conventional radiation-therapy facilities, radiation doses to medical personnel originate from the leakage radiation of 60Co teletherapy systems or from photoneutrons produced during the operation of x-ray generators at energies over 10 MeV in unsuitably shielded therapy rooms. In neutron-therapy facilities, during patient set-ups and position verifications, medical personnel are exposed to photons from remanent radioactivity induced in the shielding around the neutron-producing targets and in the beam collimators. At Fermilab, the use of an elevating platform limits personnel exposure periods to those times when collimators are being exchanged. Comparisons with other facilities are shown.