Considerations on the use of 14 MeV neutrons for radiotherapy

An experimental arrangement for shielding a Services Electronic Research Laboratory sealed tube neutron source is briefly decribed, and the properties of the resultant neutron beams are summarized. At 55 cm from the target a dose-rate of 5 rads/minute is obtained and the percentage depth dose at 10 cm deep to a 10 × 10 cm field is 40 per cent. The beam will be used in the first instance to study skin reactions during treatment of advanced pelvic cancer. The principles involved in setting up a clinical trial for fast neutron radiotherapy are discussed.