Dosimetric characteristics of the ¹⁹²Ir high-dose-rate afterloading brachytherapy source

For the treatment of some cancerous tumors using brachytherapy, an American Association of Physicists in Medicine (AAPM) Task Group No. 43U1 report recommends that the dosimetric parameters of a new brachytherapy source must be determined in two experimental and Monte Carlo theoretical methods before using each new source clinically. This study presents the results of Monte Carlo calculations of the dosimetric parameters for a Ir2.A85-2 brachytherapy source design.

Version 5 of the (MCNP) Monte Carlo radiation transport code was used to calculate the dosimetry parameters around the source.

The Monte Carlo calculated dose rate constant, Λ, of the Ir2.A85-2 source was found to be 1.113 ± 0.033 cGyU(-1)h(-1). Also in this study, the line-source radial dose function, g ( l )(r) and the anisotropy function, F(r,θ), have been calculated at distances from 0.5 to 10 cm. The results of these calculations have been compared with the published data for the same source.

All the results are in good concordance with previously published data, with a few exceptions in small angles and short distances. The dosimetric parameters calculated in this work can be used as input data in a treatment planning system (TPS) for exact brachytherapy treatment planning or to verify the calculations of the TPS used in brachytherapy.