Fabrication and Dosimetric Characteristics of Silicon Elastomer-Based Bolus Using External Beam Radiotherapy

OBJECTIVE: A study on dosimetric characteristics of silicon elastomer-based bolus was carried out using a Linear accelerator (Varian – Unique Performance). The study is performed to know if the silicone elastomer based bolus can be used in the radiotherapy. A bolus is a tissue equivalent material used to provide uniform dose to the uneven surface contours. It is exposed during the radiation therapy and also provides maximum dose (dmax) to treat surface tumors in case of high energy photons like megavoltage therapy photons. It is used in the case of external beam radiation therapy. METHODS: In this study, the bolus was fabricated using PDMS substrate with a curing agent by the ratio of 10:1. The bolus was fabricated in two thicknesses 0.5cm and 1cm. The dosimetric characteristics like transmission factor, mass attenuation coefficient, durability, homogeneity, density test of the fabricated bolus were studied. RESULTS: The dosimetric characteristics of the silicone elastomer based bolus were studied over a period of one month by exposing it in a 6MV photon. The result of the study shows that the silicone elastomer based bolus fabricated, satisfies the dosimetric characteristics needed for a tissue equivalent bolus to be used in the radiation therapy. CONCLUSIONS: The fabricated bolus could increase the percentage surface dose, reduce skin-sparing effect, and protect OAR. The aim of this is to provide an adjustable, transparent, and easily fabricated, less expensive, nontoxic bolus which can be used in the radiotherapy.