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

Abstract

IntroductionSince the heart of the electronic brachytherapy system is a tube of a miniature x-ray and due to the increasing use of electronic brachytherapy, there is an urgent need for acquiring knowledge about the X-ray spectrum 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.MethodsConsidering the advantages of MCNPX Code (2.6.0), two input files corresponding to the characteristics of the investigated miniature sources were prepared for this code and then were used for simulation. The optimal thickness (OT) of gold and tungsten targets was determined for the energy levels of 40, 45, and 50 kilo-electron-volts.ResultsIn this study, the values of the size of the optimal thickness of 0.92, 1.01 and 1.06 μ for gold target and values of 0.99, 1.08 and 1.34 μ for tungsten target were obtained for energies 40, 45 and 50 keV that using these values, the optimum thickness of 0.92, X-ray spectrum within and outside targets, axial and radial doses for the used energy were calculated for two miniature sources.ConclusionIt was found that the energy of incident electron, target shape, cross-sectional area of the produced bremsstrahlung, atomic number of materials constituting of the target and output window are the factors with the greatest impacts on the produced X-ray spectrum and the absorbed dose.

The Effect of Anode, Hot and Cold Cathode Structures Used in Miniature X-Ray Tubes on X-Ray Output Using Monte Carlo Simulation

“…The hot tungsten cathode can work even in non-ultra-high vacuum environments containing a large number of gas molecules. However, hot cathodes are exposed to chemical reactions that generate tungsten oxides, which become thinner over a long period by sublimation of oxides [5]. Therefore, X-ray production with this method faces limitations such as gradual response time, high energy consumption, and time limit.…”

“…In the mid-1950s, replacing cold cathodes with hot cathodes was suggested to overcome the disadvantages of hot cathodes [5]. Accordingly, the X-ray production using the field emission method was first reported in 1956 [6].…”