Comparisons of the Codes of Practice IAEA TRS 277 and TRS 398: High Energy Photons and Electron Beams

摘要

This work presents the calibration for: 6, 8, 10, 12, 14, 15 and 18 MeV electron beams, also to 6 and 15 MV photons beams. Beams that are generated by an accelerator Elekta Linac SL 18. The calibration is performed in terms of absorbed dose to water D_w. It is determined by two different protocols: the code of practice of the International Atomic Energy Agency (IAEA) TRS 277 for ionization chambers calibrated on air kerma N_K, and the code of practice TRS 398 for ionization chambers calibrated on absorbed dose to water N_(D,W). Two independent dosimeters were used with two ionization chambers each one, respectively. The first one, a dosimeter PTW model UNIDOS with Markus type chamber (plane parallel) for electrons, and Farmer type chamber (cylindrical) for photons, both chambers calibrated in N_K. The second dosimeter Scanditronix model DOSE 1 with plane parallel chamber (electrons) and cylindrical chamber (photons), both chambers calibrated in terms of N_(D,W). In the case of photon beams, the TPR was measured for 6 and 15 MV, also the profiles were determined in order to verify the flatness and symmetry of the beam: ±3%. The quality for electrons beams were estimated by means of the D_(max), R_(80), R_(50) and R_p. The results obtained for the absorbed dose quotients D_(W,Q)(d_(max))_(277)~(398) are: Electrons, 0.976 ≤ D_(W,Q)(d_(max))_(277)~(398) ≤ 1.001; Photons: 1.001 ≤ D_(W,Q)(d_(max))_(277)~(398) ≤ 1.003.