A Monte Carlo investigation of the dosimetric characteristics of the VariSource 192Ir high dose rate brachytherapy source

An analytical Monte Carlo simulation code, incorporating in detail source construction and dimensions, was used to investigate the dosimetric characteristics of the VariSource Ir-192 high dose rate brachytherapy source. Dose-rate constant, radial dose functions, and anisotropy functions, utilized in the AAPM Task Group 43 dose estimation formalism, were calculated with the source centered in a spherical water phantom of 30 cm in diameter. The results, which are in agreement with the corresponding data available in the literature, are compared to those obtained in our previous study for the widely used microSelectron Ir-192 high dose-rate brachytherapy source. The dose-rate constant was found to be equal to 1.043+/-0.005 cGy h(-1) U-1 for the VariSource, compared to a value of 1.116+/-0.006 cGy h(-1) U-1 calculated for the microSelectron. Significant differences in the anisotropy of the two sources are observed only for polar angles close to their long axis and are due to their different dimensions. (C) 1999 American Association of Physicists in Medicine. [S0094-2405(99)03008-4].