Dosimetric investigation of LDR brachytherapy ¹⁹²Ir wires by Monte Carlo and TPS calculations

Purpose: The aim of this study was to investigate the dose rate distribution around ¹⁹²Ir wires used as radioactive sources in low-dose-rate brachytherapy applications. Materials and methods: Monte Carlo modeling of a 0.3-mm diameter source and its surrounding water medium was performed for five different wire lengths (1-5 cm) using the MCNP software package. Results: The computed dose rates per unit of air kerma at distances from 0.1 up to 10 cm away from the source were first verified with literature data sets. Then, the simulation results were compared with the calculations from the XiO CMS commercial treatment planning system. Conclusion: The study results were found to be in concordance with the treatment planning system calculations except for the shorter wires at close distances.