Dose distribution in water for monoenergetic photon point sources in the energy range of interest in brachytherapy: Monte Carlo simulations with PENELOPE and GEANT4

Monte Carlo calculations using the codes PENELOPE and GEANT4 have been performed to characterize the dosimetric properties of monoenergetic photon point sources in water. The dose rate in water has been calculated for energies of interest in brachytherapy, ranging between 10keV and 2MeV. A comparison of the results obtained using the two codes with the available data calculated with other Monte Carlo codes is carried out. A χ2-like statistical test is proposed for these comparisons. PENELOPE and GEANT4 show a reasonable agreement for all energies analyzed and distances to the source larger than 1cm. Significant differences are found at distances from the source up to 1cm. A similar situation occurs between PENELOPE and EGS4