Abstract

Radiation quality of fast neutron beams used for radiation therapy can change with depth, the primary effect being a 'hardening' of the neutron beam produced by the scattering of slow neutron components. We report measurements of microdosimetric spectra in phantom, with and without hardening filter, for the 62 MeV p®Be [p(62)+Be] machine at the MRC Cyclotron Unit at Clatterbridge Hospital. Comparison is made with similar measurements on the 42 MeV beam [p(42)+Be] at M.D. Anderson Hospital. An interesting observation is the comparison of results obtained with differing counters and phantoms, which demonstrate that these parameters can have a non-negligible effect on intercomparisons between machines.

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