Investigation of surface and buildup region doses for6 MV high energy photon beams in the presence of athermoplastic mask

Background: the accuracy and the reproducibility of radiotherapy can beprovided by using immobilization devices such as thermoplastic masks. inhead and neck cancer radiotherapy, the patients are mostly immobilized byusing thermoplastic masks. in this study, the effect of the thermoplastic maskto the surface and buildup region doses was investigated by using markusparallel plate ion chamber, gafchromic ebt3 film and mosfet detector forthe same field size and different beam angles. materials and methods: themeasurements were made in a water equivalent solid phantom at the surfaceand in the buildup region of the 6 mv photon beams at 100 cmsource-detector distance for 10 × 10 cm2 field size and beam angles of 0°, 30°,60° and 80° with and without thermoplastic mask. results: the surface dosesin 0.07 mm depth using 6mv photon beams without a thermoplastic mask for10 × 10 cm2 field size were found 20.3%, 18.8%, and 41.5% for markuschamber, ebt3 film, and mosfet detector, respectively. the surface dosesusing 6 mv photon beams with a thermoplastic mask for 10 × 10 cm2 field sizewere found 38.4%, 51.7% and 50.2% for markus chamber, ebt3 film, andmosfet detector, respectively. conclusion: the thermoplastic masks placedon the surface of the medium affect the surface and buildup region doses.the effect of thermoplastic masks to surface and buildup region doses shouldbe determined before use clinically