SHIELDING VARIATION EFFECTS FOR 250 MeV PROTONS ON TISSUE TARGETS

As the number of medical hadron therapy centres worldwide is growing, Austria has also planned to invest in such a facility. The MedAustron project for a proton and carbon ion accelerator facility is approaching the end of its planning phase. To ensure radiation safety for personnel, patients and third persons involved in therapy treatment, extensive studies to determine the dose distributions in various work environments will have to be conducted. This work deals with basic shielding studies for practical radiation protection purposes around medical therapy threatment rooms. The computer simulation models consist of simple cylindrical room geometries rather than rectangular room shapes and labyrinth entrances. Varying wall thickness is modelled for determining particle fluence and dose distributions behind different shielding materials. Tissue-equivalent targets of simple geometries simulating the patient are situated in the centre of the treatment room. As the maximum energy of the MedAustron proton accelerator is in the range of 250 MeV, this is also the energy chosen for the work presented in this paper. Results obtained by the computer simulations can thus be viewed as a worst case study. Given the beam, room and patient parameters, Monte Carlo simulations of the energy and angular dependence of proton, neutron and photon radiation fields and resulting H* (10) ambient dose equivalent distributions outside the shielding walls are performed. Various concrete compositions, densities and water contents are modelled. A direct comparison between the results of the Monte Carlo transport codes MCNPX (1) and FLUKA (2) is provided in this paper, together with a comparison to data from the current literature.