AN EVALUATION OF THE RECOMMENDATIONS OF THE TG-25 PROTOCOL FOR DETERMINATION OF DEPTH-DOSE CURVES FOR ELECTRON-BEAMS USING IONIZATION CHAMBERS

AAPM Radiation Therapy Committee Task Group 25 has recently outlined a protocol for the determination of relative dose curves for electron b eams [Med. Phys. 18, 73-109 (1991)]. We have performed an evaluation o f this protocol by comparing the central axis depth dose curves determ ined from measurements using two different ionization chambers and thr ee different phantom materials. Measurements were made with a Farmer-t ype PTW and Capintec ionization chamber in solid water, PMMA, and clea r polystyrene phantoms irradiated by 6- and 15-MeV electron beams. Cen tral axis depth dose curves were generated from the measured depth-ion ization data using the new protocol. For both the chambers and energie s investigated in this study, excellent agreement was observed among a ll the depth doses in water obtained from measurements in all of the t hree phantoms studied.