Verification of LDR brachytherapy dose distributions for different source geometries by Monte Carlo method

OBJECTIVES: This study aimed to verify dose distributions for 192Ir wires obtained from both the CMS XiO treatment planning system (TPS) and the Monte Carlo (MC) method. METHODS: Using 192Ir source of 1.84 mCi/cm activity, three different wire setups were investigated. Whole properties of the wires were modelled in the MC code MCNP. Dose distributions and isodose curves were obtained and then compared with TPS results. RESULTS: Isodose curves from TPS and MC were found to differ as 0.28 mm, 0.4 mm and 0.57 mm for one, two and three wire applications, respectively. MC was observed to yield much narrower isodose curves. CONCLUSION: The greater the number of wires, the larger the differences between the isodose widths calculated with TPS and MC. However, these differences are less than 1 mm. The results show that, for low dose rate (LDR) brachytherapy applications, CMS XiO TPS and MC yield consistent isodose curves.