A Monte Carlo simulation of fast neutron beams used for radiotherapy: I. Dose deposition by a collimated (d, t) beam

Fast neutron and proton therapy sources

Neutrons from the reactions of protons or deuterons of energies between 35 and 70 MeV on beryllium are most suitable for therapy because of the high yield and good penetration. Lower energy sources are used for limited applications. Proton therapy is conducted mainly in two energy ranges, viz. 60–75 MeV (exclusively for the treatment of eye lesions) and ≥200 MeV for general applications. Characterisation of both neutron and proton therapy beams in terms of spectral fluence is important for accurate determination of dosimetry parameters, for interpreting biological effects, for intercomparison purposes and to perform accurate radiation transport calculations.