DEPTH DOSE AND STOPPING-POWER DATA FOR MONOENERGETIC ELECTRON-BEAMS

The determination of absorbed dose to water in electron beams from ionization measurements in a phantom is based today mainly on data computed with the Monte Carlo code ETRAN. Changes in the energy-loss sampling procedure of ETRAN have produced significant modifications in electron transport results used in electron dosimetry. The magnitude of the changes in electron data in the energy interval used in radiation therapy with electron beams has been investigated using other Monte Carlo codes (MCEF, EGS, ITS). The depth-dose data and water/air stopping-power ratios are compared with the existing results calculated with ETRAN for a wide energy range of broad plane-parallel monoenergetic electron beams and an alternative set of data has been computed. Calculations of water/air stopping-power ratios using different sets of density-effect corrections have been performed. The influences on the dosimetry of electron beams given the present state of knowledge of electron stopping-powers is discussed. © 1990.