Promising application of nano-WO₃/epoxy composite in intensity-modulated brachytherapy: a simulation study

Purpose: Implementing intensity-modulated brachytherapy (IMBT) techniques with high-energy sources like 60Co has always been challenging due to the clinical limitations of the applicator dimensions. This study aims to investigate using tungsten trioxide nanoparticles/epoxy composite as a shielding material to enhance the protective properties of a redesigned applicator. Materials and Methods: The Geant4 application to tomographic emission, the Geant4-based Monte Carlo dose calculation engine (version 9.0), was used to simulate the shielding composite and the IMBT technique with a voxelated patient-based phantom. To evaluate the effectiveness of the new shielding material, IMBT plans created with the redesigned applicator were compared with those with a conventional applicator. 60Co and 192Ir were utilized, and in the same high-risk clinical target volumes D90, the D2cc for the bladder and rectum were evaluated in 18 patients with vaginal cancer. Results: For the IMBT plans with the 60Co source, the use of the redesigned applicator decreased the D2cc of the bladder and rectum by 11.1% and 12.8%, respectively, while for those with the 192Ir source, the reduction was 16.6% and 18.7%, respectively. Nevertheless, there was an insignificant alteration in the absorbed dose parameter (D90) for the target using both sources. Conclusion: This study demonstrates that tungsten trioxide nanoparticle/epoxy composite can be advantageous in tackling radiation shielding concerns. Enhancing the shielding properties of this composite, considering the size limitations of applicators, leads to improved protection of organs at risk, such as the bladder and rectum. This substance can be considered a promising shielding material in the construction of applicators.