Fabrication of Alternative Bolus for Cobalt-60 Teletherapy Using Two Locally Available Materials

Bolus is a tissue equivalent material which is use in radiation therapy in order to eliminate skin sparing effect of higher energy photon beams that always reduce the surface dose. There are several commercially bolus material such as Superflab, Aquaplast and gels for use but literature have shown that they are expensive and are not readily available in developing countries. This work presents the fabrication of an alternative bolus for Cobalt-60 Teletherapy using two locally available materials (Beeswax and Petroleum jelly). Beeswax was liquefied at a temperature of 60°C followed by the addition of Petroleum jelly at ratio 3:1 by weight for proper molding and flexibility. In order to determine the depth of maximum dose, Thermoluminescent Dosimeter (TLD) chips were inserted in between ten bolus materials of thickness 0.5 cm that were arranged in layers and placed on a solid water phantom. This was then irradiated with Cobalt-60 radiation source using field size ranging from 5 cm x 5 cm to 10 cm x 10 cm field size. For all the field size, maximum absorbed dose was found to be at 0.5 cm depth. This depth of maximum dose was compared to two tissue equivalent materials in use in radiation therapy: water and Superflab for Cobalt-60 Teletherapy and found to be in agreement. The percentage dose deviation when compared with water for 1 cm, 2 cm, 3 cm, 4 cm and 5 cm were less than 2%. The flexibility of the bolus material and the analysis of the absorbed dose measured have shown that the fabricated bolus material of thickness 0.5 cm can be used as an alternative bolus material for Cobalt-60 Teletherapy.