Physical characteristics of fast-neutron beams from a compact medical cyclotron.

A fast-neutron therapy facility is planned for a compact medical cyclotron. Energy spectra and yields of neutrons produced in a thick beryllium target by deuterons and protons were investigated. Collimator performance, shielding design, and central-axis depth doses were calculated by means of a Monte Carlo computer program. This facility appears adequate for clinical trials on certain tumors of the head and neck.