Assessment of two hemispherical and hemispherical-conical miniature sources used in electronic brachytherapy using Monte Carlo Simulation

摘要

Introduction: Since the heart of the electronic brachytherapy system is a tube of a miniature x-ray and due to theincreasing use of electronic brachytherapy, there is an urgent need for acquiring knowledge about the X-rayspectrum produced, and distribution of x-ray dose. This study aimed to assess the optimal target thickness (TT),the X-ray source spectrum, and the absorbed dose of two miniature sources of hemispherical and hemispherical- conical used in electronic brachytherapy systems, through a Monte Carlo simulation.Methods: Considering the advantages of MCNPX Code (2.6.0), two input files corresponding to thecharacteristics of the investigated miniature sources were prepared for this code and then were used forsimulation. The optimal thickness (OT) of gold and tungsten targets was determined for the energy levels of 40,45, and 50 kilo-electron-volts.Results: In this study, the values of the size of the optimal thickness of 0.92, 1.01 and 1.06 μ for gold target andvalues of 0.99, 1.08 and 1.34 μ for tungsten target were obtained for energies 40, 45 and 50 keV that using thesevalues, the optimum thickness of 0.92, X-ray spectrum within and outside targets, axial and radial doses for theused energy were calculated for two miniature sources.Conclusion: It was found that the energy of incident electron, target shape, cross-sectional area of the producedbremsstrahlung, atomic number of materials constituting of the target and output window are the factors with thegreatest impacts on the produced X-ray spectrum and the absorbed dose