comparison of megavoltage electron dosimetry beams in radiation therapy using different protocols

Background: international atomic energy agency (iaea) and american association of physicist in medicine (aapm) have introduced new protocols for dosimetry of electron and photon megavoltage beams and increased them to more than five protocols at the beginning of new decade. selecting a protocol by medical physicists and acquiring skill for using reference conditions and recommended formulation by each protocol necessitate recognition of various dosimetry protocols. the aim of this study was to compare the protocols trs-277, trs-381, and trs-398 of iaea for megavoltage electron beams used in radiation therapy.methods: comparison of trs-398 with other protocols was done as follows:1. measurement and estimation of the absorbed dose of 6mev neptun 10 linear accelerator through ionization chamber with parallel nacp plates in water phantom and acrylic.2- measurement of the absorbed dose in 17mev saturn 20 linear accelerator through ionization chamber with parallel nacp plates in water phantomresults: the results indicated that the differences observed between the protocols compared to trs-398 protocol was between -4.9 and 0.2%; the highest difference was related to 17 mev electron beam using trs-277 protocol.conclusions: according to the results, the considerable difference observed in 17mev electrons was related to trs-277 and trs-388 protocols. given that calibration ratio of the absorbed dose in air is used in the trs-277 protocol, the difference obtained was related to the application of secondary calibration used in this research.