SU‐GG‐T‐03: Dosimetric Study of HDR 192Ir and LDR 125I Brachytherapy Sources Using the Penelope Monte Carlo Code

Purpose: To determine the dosimetric parameters of two HDR models 192Ir (microSelectron, and M‐19), and LDR 125I brachytherapy sources. Method and Materials: In this study we used the192 Ir microSelectron and M‐19 models, and also125 I source (Amersham OncoSeed model 6711). Penelope Monte Carlo transport code was used. All the photonic interactions were taking into account. AAPM TG‐43 was followed to determine the dosimetric properties 1 . 2D dose distribution, dose rate constant, anisotropy and radial dose functions were determined. Results: For both Iridium models, the 2D‐dose distribution agrees very well with published data for radius 1 ⩽ r ⩽ 5 cm, the difference was less than 3 %. The dose rate constant is 1.11654 cGy h −1 U −1 for microSelectron and 1.12456 cGy h −1 U −1 M‐19 model. Less than 3 % difference was observed for the radial dose function for radius 1 < r < 5 cm for both Iridium models. The DRC for125 I was found to be 0.984 cGy h −1 U −1 , and less than 3 % difference for the radial dose function in comparison with published data in TG‐43. Conclusion: Extensive work had been done on192 Ir and125 I brachytherapy sources. Daskalov et al 2 , Medich et al 3 , and Granero et al 4 , used different192 Ir source models and different Monte Carlo transport codes, but the difference for the dosimetric parameters between all these studies was less than 5 %. In this study we used Penelope Monte Carlo code to determine the dosimetric parameters. The results showed 3 % difference for 2D dose distribution, DRC, and radial dose function for Iridium sources and 3 % difference for Iodine source.