Evaluation of hypothetical 153Gd source for use in brachytherapy

AimThe purpose of this work is to evaluate the dosimetric parameters of a hypothetical 153Gd source for use in brachytherapy and comparison of the dosimetric parameters with those of 192Ir and 125I sources.Materials and methodsDose rate constant, the radial dose function and the two dimensional (2D) anisotropy function data for the hypothetical 153Gd source were obtained by simulation of the source using MCNPX code and then were compared with the corresponding data reported by Enger et al. A comprehensive comparison between this hypothetical source and a 192Ir source with similar geometry and a 125I source was performed as well.ResultsExcellent agreement was shown between the results of the two studies. Dose rate constant values for the hypothetical 153Gd, 192Ir, 125I sources are 1.173 cGyh−1 U−1, 1.044 cGyh−1 U−1, 0.925 cGyh−1 U−1, respectively. Radial dose function for the hypothetical 153Gd source has an increasing trend, while 192Ir has more uniform and 125I has more rapidly falling off radial dose functions. 2D anisotropy functions for these three sources indicate that, except at 0.5 cm distance, 192Ir and 125I have more isotropic trends as compared to the 153Gd source.ConclusionA more uniform radial dose function, and 2D anisotropy functions with more isotropy, a much higher specific activity are advantages of 192Ir source over 153Gd. However, a longer half-life of 153Gd source compared to the other two sources, and lower energy of the source with respect to 192Ir are advantages of using 153Gd in brachytherapy versus 192Ir source.