Calculation and approximation of radial dose function of iridium sources

Background and Objectives: The purpose of this paper is to investigate optimal fitting parameters for approximating radial dose function of Iridium sources. Calculations were performed using written by authors source code based on GEANT4 library package designed to simulate particle transport processes using Monte–Carlo method. Results: Following parameters of the source were determined: dose rate constant, radial dose function and anisotropy function. Obtained satisfactory coherence with other researchers’ data. The data obtained using developed and verified code could be used in treatment planning system (TPS). In addition, this paper presents improved functional form for fitting radial dose function (RDF) brachytherapy sealed sources with Ir-192. Suggested functions allow for fitting RDF precisely in a range of 0,5–20 cm. Maximum deviations between fit data and Monte–Carlo simulation data don’t exceed 0,6%, while average deviation is around 0,1%. Fitting coefficients for suggested functions are presented for 11 sources from different manufacturers.Conclusion: Suggested functions are suitable for using in TPS to calculate radial dose distributions around sources more precisely, using broad range of data using TG-43 protocol.