Physical and radiobiological parameters of proton beams up to 31 MeV

Summary Frequency distributions of energy deposition in microscopic tissue volumes determined by means of a ?Rossi type? proportional counter for 31, 12 and 8 MeV proton beams and, dose response curves for mortality and chromosome aberrations in cultured human cells exposed to the same beams are analysed with a view to determining suitable parameters to specify radiation quality. The behaviour of quantities LET,Z ^*2/β² and the microdosimetric parameter as a function of energy are compared with the corresponding behaviour of the most significant radiobiological parameters as mean lethal dose per targetD ₀, mean inactivation dose , intensity of chromosome aberrations, and dicentrics. It is shown that is the most suitable physical parameter to characterize the relative effectiveness of protons in the (8÷31) MeV range. Work partially supported by grant No. 8000165896 for the Finalized Project ?Tumor Growth Control?.