Microdosimetry in anthropoid phantoms

3-D Monte-Carlo calculations of radiation transport throughout anthropoid phantoms have been performed for incident neutrons of energies from thermal up to 20 MeV. The resulting charged particle emission spectra were used in the subsequent calculations of energy transfer to tissues, using the continuous slowing down approximation. Energy deposition to the assumed sensitive sites has been described using the analytical approaches based on chord length distributions and, for nanometric sites, on the results of track structure calculations. Resulting microdosimetric spectra are the physical measure of radiation quality. They strongly depend on the assumed dimensions of sensitive sites and considerably differ from organ to organ. The in-body microdosimetric distributions have been subsequently convoluted with the phenomenological biological response functions for some selected endpoints of a stochastic nature, based on interpretation of the results of in vitro experiments, thus resulting in absolute risk estimates for particular effects in organs. These estimates have been compared with equivalent doses in tissue, HT, calculated for the same phantoms according to the recent ICRP recommendations. (author)