Activation of the major constituents of tissue and air by a fast neutron radiation therapy beam.

The production of 11C, 13N, 15O from C, N, O, and of 39Cl and 41Ar from Ar by a p(66)Be(49) clinical neutron therapy beam has been measured. The results of these measurements were used to estimate the production of other radionuclides, then to estimate airborne radioactivity in a typical neutron therapy room and radioactivity induced in body tissues during treatment. Only under special circumstances would airborne radioactivity necessitate a waiting period before entering a typical treatment room. The additional dose to a treatment volume due to decay products from radioactivity induced within that volume would amount to a few thousandths of the given dose and the additional body dose outside the treated volume would be a few millionths of the given dose.