CHARACTERIZATION OF CLINICAL ELECTRON BEAMS BY MONTE CARLO SIMULATION AND ITS COMPARISON TO THE PROTOCOLS USED IN DOSIMETRY

To help medical physicist to evaluate dose values due to direct application of electron beams we have simulated the process using Monte Carlo methodology to calculate the energy deposited in a water phantom and compared to the measured values with the tridimensional dosimetric system. Percentage depth dose curves have been obtained using the well-known Monte Carlo codes: MCNP-4C and its newest version, MCNP5. The measured data were used to obtain mean energy at the phantom surface, 0E, maximum depth dose, R100, and the depth of 50 % ionization, R50 following the International Atomic Energy Agency (IAEA) Report No381 and No398, the American Association of Physicists in Medicine (AAPM) Task Group 21 and the NACP protocols. It was found a small difference between the results presented by the different protocols that depends on the depth considered. Comparison with calculated values have shown maximum discrepancies of the order of 3.4, 3.8 and 4.7 % respectively for R50, R100 and 0E for 6 MeV beam and 2.3, 18 and 2.5 % for 12 MeV beam