Calculations of absorbed dose and energy dependent of small-scale dosimeters for photons beam therapy

In this study, the energy dependency for dosimeters of air ionization chambers, lithium fluoride, silicon and plastic scintillator has been studied using the MCNPX Monte Carlo simulation code and simulated for gamma energy in the range of radiotherapy energy. The simulation results show that the response of each of the dosimeters for gamma photon beams in the energy range of 0.2 to 20 MeV varies. Dependence of dose to energy for the air ionization chamber dosimeter is higher than other dosimeters. Among the dosimeters under study, the ratio of absorbed dose of plastic scintillator to the absorbed dose of water in the energy range indicates the lowest dependence to energy. The results of the absorbed dose of the dosimeters to the absorbent dose of water show that the plastic scintillator has the highest and the silicon has the lowest equivalence with water. In the analytical studies, the ratio of absorbed dose of the dosimeters to the absorbed dose of water was calculated using the Berlin theory and compared to Monte Carlo results. Comparisons show good agreement between analytical and simulation results.