Proton scattering power of some tissue-equivalent plastics

Proton scattering in some water and tissue equivalent phantom materials was measured to evaluate their simulation accuracy of water and respective human biological tissues. The measurements were performed on the medical facility of the ITEP synchrotron, proton energy was 219 MeV, a narrow beam was formed by a 3 mm collimator. A stack of plastic slabs was set closely to the collimator hole as a scatterer. Three types of Plastic Water (PW, PW LR and PW DT), lung, cortical bone, adipose and muscle plastics (CIRS Inc., USA) were used in the experiments as the substitutes under investigation and liquid water and PMMA slabs as reference materials. Dose (intensity) profiles were measured for each sample by two orthogonal strips of the Gafchromic EBT film. A total thickness of the plastic slab was from 4 to 16 cm depending on the material. The Gafchromic film response nonlinearity was taken into account by an additional calibration vs. absorbed dose in a wide proton beam, the temporal irradiation-to-scanning dependence was also accounted. The central part of each angular distribution was fitted by the Gaussian function and compared with the respective parameters calculated for the simulated medium by Monte Carlo technique with the IThMC code.