Characterization of in-house bolus materials for electron beam radiotherapy

Bolus in radiotherapy is not only used as a compensator for irregular body surfaces, but it is also used to enhance the surface dose and decrease the depth range dose. Nowadays, "in-house boluses"or artificial boluses are being evolved, as they are designed by medical physicists to match the patients' needs and to be made of low-cost materials. This research aims to create 15x15x1cm3 in-house boluses which are made of various materials such as silicone rubber, 3D printed TPU, resin, and silicone sealant. It also aims to determine the Relative Electron Density (RED) value, the absorption dose, and the Percentage of Surface Dose (PSD) of each bolus at 10 MeV and 12 MeV electron beam irradiation. The in-house bolus was irradiated by using Linac Elekta Synergy Platform with 10x10 cm2 irradiation field area, 100 cm SSD, and radiation dose of 200 MU min-1. The RED value was obtained by processing the CT-Scan image using radiAnt software. The results show that the RED value of silicone rubber, 3D print TPU, and silicone sealant boluses are close to the RED value of some hard tissues, while the RED value of resin is close to the RED value of soft tissues. Furthermore, various in-house boluses in this research were proven to be able to reduce the depth range of absorption dose and enhance the percentage of surface dose to 100% for the electron beam irradiation.