Determination of task group 43 dosimetric parameters for CSM40 137 Cs source for use in brachytherapy.

The CSM40 137 Cs source model is currently being used in clinical brachytherapy. According to the recommendations of task group No. 43 (TG-43) of the American Association of Physicists in Medicine, dosimetry parameters of brachytherapy sources should be determined by two independent investigators before their clinical use. The aim of this study was to determine the TG-43 dosimetry parameters for a medium-dose-rate CSM40 137 Cs source. The determined dosimetric parameters included the air kerma strength, dose rate constant, radial dose function, and anisotropy function. To determine the source's dosimetric parameters, the CSM40 source was stimulated by the Monte Carlo N-Particle MCNP code. The TG-43 parameters were compared with the data of Vijande et al. on this source. The results showed that the dosimetry parameters for this source had good agreement with the results of Vijande et al. The dosimetric parameters of the CSM40 source can be used in treatment-planning systems incorporating this source model. The data can also be used for the quality assurance of treatment-planning systems.