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Differences in electron depth‐dose curves calculated with EGS and ETRAN and improved energy‐range relationships

1986; Wiley; Volume: 13; Issue: 5 Linguagem: Inglês

10.1118/1.595831

2473-4209

D. W. O. Rogers, Alex F. Bielajew,

Radiation Effects and Dosimetry

For 1–50 MeV electrons incident on a water phantom there are systematic differences in the depth‐dose curves calculated by the Monte Carlo codes EGS and ETRAN (and its descendants SANDYL, CYLTRAN, ACCEPT, and the ITS system). Compared to ETRAN, the EGS code calculates a higher surface dose and a slightly slower dose falloff past the dose maximum. The discrepancy in the surface dose is shown to exist because the modified Landau energy‐loss straggling distribution used in ETRAN underestimates the mean energy loss by about 10% since it underestimates the number of large energy loss events. Comparison to experimental data shows a preference for the EGS depth‐dose curves at 10 and 20 MeV. Since various dosimetry protocols assign electron beam energies based on measured depth‐dose curves in water, formulas based on these more accurate EGS4 calculations are presented: (i) relating the mean energy of an incident electron beam to R 5 0 , the depth at which the dose in a water phantom falls to 50% of its maximum value; and (ii) relating the most probable energy of the incident beam to the projected range of the depth‐dose curve. A study is presented of the effects of the incident electron spectrum on the calculated depth‐dose curve.