Determination of TG-43 Dosimetric Parameters for Photon Emitting Brachytherapy Sources

Brachytherapy sources are widely used for the treatment of cancer. The report of Task Group No. 43 (TG-43) of American Association of Physicists in Medicine is known as the most common method for the determination of dosimetric parameters for brachytherapy sources. The aim of this study is to obtain TG-43 dosimetric parameters for ⁶⁰Co, ¹³⁷Cs, ¹⁹²Ir and ¹⁰³Pd brachytherapy sources by Monte Carlo simulation.

In this study, ⁶⁰Co (model Co0.A86), ¹³⁷Cs (model 6520-67), ¹⁹²Ir (model BEBIG) and ¹⁰³Pd (model OptiSeed) brachytherapy sources were simulated using MCNPX Monte Carlo code. To simulate the sources, the exact geometric characterization of each source was defined in Monte Carlo input programs. Dosimetric parameters including air kerma strength, dose rate constant, radial dose function and anisotropy function were calculated for each source. Each input program was run with sufficient number of particle histories. The maximum type A statistical uncertainty in the simulation of the ⁶⁰Co, ¹³⁷Cs, ¹⁹²Ir and ¹⁰³Pd sources, were equal to 4%, 4%, 3.19% and 6.50%, respectively.

The results for dosimetry parameters of dose rate constant, radial dose function and anisotropy function for the ⁶⁰Co, ¹³⁷Cs, ¹⁹²Ir and ¹⁰³Pd sources in this study demonstrated good agreement with other studies.

Based on the good agreement between the results of this study and other studies, the TG-43 results for Co0.A86 ⁶⁰Co, 67-65200 ¹³⁷Cs, BEBIG ¹⁹²Ir and OptiSeed ¹⁰³Pd sources are validated and can be used as input data in treatment planning systems (TPSs) and to validate the TPS calculations.