Brachytherapy Dosimetry Parameter Measurement for Cobalt-60 Source using Monte Carlo Simulations Geant4, and Comparing the Results with Standard BEBIG Source

Abstract

Background: Brachytherapy is used to treat cancer in a short distance with radiation from the radionuclide sources located inside the capsule. This type of treatment is directly treated with direct irradiation, in or near the treatment area; then the dose is continuously delivered to the tumor. In protocol of TG-43, we use air kerma strength, dose rate constant, radial dose function, and anisotropy function to calculate the distribution of doses around any linear source. The purpose of this study was to calculate and obtain dosimetric parameters for the cobalt-60 source, using the Geant4 code, and comparing with the reference calculations of the BEBIG cobalt source. Methods: By using Geant4 code, cobalt source and water phantom were simulated for dosimetry calculations. The average energy of gamma rays in simulation was considered for gamma rays from cobalt-60 source. Findings: The results of simulation performed by Monte Carlo Geant4 method was obtained in the form of dose distribution curves and important parameters in the dosimetry of brachytherapy, according to protocol recommendations of TG-43U1 with low error percentage. Moreover, dosimetric quantities including air kerma intensity, radial dose function, two-dimensional anisotropy function for angles of 0 to 90 degrees, dose rate constant, and optical density reduction were calculated. Dose rate constant was obtained as equal to 1.086 ± 0.003 cGyh-1U-1. Conclusion: Calculations performed with the Geant4 code show a good agreement after comparing with BEBIG cobalt reference data. Dosimetric parameters obtained from the simulation based on the TG-43U1 protocol can be used in brachytherapy treatment design software.

Keywords

• brachytherapy
• radiation dosimetry
• cobalt