Effects of dose fractionation after irradiation with neutrons produced by 600 MeV protons

Biological effects produced by neutrons of various energies up to 15 MeV have been extensively studied through their use in therapeutic applications (Barendsen, 1968; Hall et al., 1973; Hornsey and Field, 1979). Possible further radiotherapeutic gains from neutrons of higher energies have been investigated recently (Harrison et al., 1976; Hall and Durand, 1980). Biological damage by neutrons with maximum energies of 400 and 600 MeV, produced by the CERN synchrocyclotron, have been investigated for several years. Un-expected effects were observed in the low-dose regions (Baarli et al., 1976; Di Paola et al., 1980; Diehl-Marshall and Bianchi, 1981).