Benchmarking EGSnrc in the kilovoltage energy range against experimental measurements of charged particle backscatter coefficients.

This study benchmarks the EGSnrc Monte Carlo code in the energy range of interest to kilovoltage medical physics applications (5-140 keV) against experimental measurements of charged particle backscatter coefficients. The benchmark consists of experimental data from 20 different published experiments (1954-2007) covering 35 different elements (4<or=Z<or=92), electron and positron backscatter, normal and oblique incidence, and backscatter from thin films. EGSnrc simulation results show excellent agreement with the vast majority of the experimental data. Possible experimental and computational uncertainties explaining the few noted discrepancies are discussed. This study concludes that for the energy range of interest to kilovoltage medical physics application, EGSnrc produces backscatter results within approximately 4% of the average of the majority of published experimental data. A documented EGSnrc user-code customized for backscatter calculations is available from the authors at http://www.physics.carleton.ca/clrp/backscatter.