In vivo prostate IMRT dosimetry with MOSFET detectors using brass buildup caps

The feasibility of using dual bias metal oxide semiconductor field effect transistors (MOSFET) detectors with the new hemispherical brass build up cap for in vivo dose measurements in Prostate IMRT treatments was investigated and achieved. A general formalism with various correction factors taken into account to predict Dmax entrance skin dose for the IMRT fields with MOSFETS was developed and compared against predicted dose from the treatment planning system. We achieved an overall accuracy better than +/- 5 % on all measured fields for both 6 MV and 10 MV beams when compared to predicted doses from Philips Pinnacle3 and CMS XiO treatment planning systems respectively. We also estimate the total uncertainty in estimation of MOSFET dose in the high sensitivity mode for IMRT therapy to be 4.6%.