Fabrication and Characterization of Bolus Material Using Propylene Glycol for Radiation Therapy

This study aimed to evaluate the efficacy of a synthesized bolus in the reduction of damage to body tissues and the protection of the organ at risk (OAR) in radiotherapy application. Several properties of the synthesized bolus, including density, transmission factor, and effective mass attenuation coefficient, were investigated.
The materials used comprising of propylene glycol (PG), silicone rubber (SR), and aluminum (Al). The dimension of the synthesized bolus was measured using an acrylic case with a size of 11×11 cm² and thickness sizes of 0.5, 1, and 1.5 cm. Furthermore, the boluses were irradiated by linear accelerator with the photon beam energies of 6 and 10 MV, using linier accelerator (LINAC) Varian 2300ix.
In this research,the density of synthesized bolus was evaluated by mass per volume equation. The results showed that the density of bolus was similar to the density of tissue/water, fat, and air. .  Furthermore the bolus with the composition of PG 24%, SR 8%, and Al 1.5% of all energies, transmission factors of 0.978 and 0.984, thickness of 1.5 cm, and effective mass attenuation coefficients of 0.0144 and 0.0107 cm²/g had the closest properties to the body tissues in terms of dosimetry characterization.
The results revealed that the synthesized bolus could increase the percentage surface dose, reduce skin-sparing effect, and protect OAR. The findings indicated that the synthesized bolus had a potential application in clinical therapy.