Comparison of MCNP4C, 4B and 4A Monte Carlo codes when calculating electron therapy depth doses

ABSTRACT

Monte Carlo simulation of radiation transport is considered to be one of the most accurate methods of radiation therapy dose calculation. There are different Monte Carlo codes for simulation of photons, electrons and the coupled transport of electrons and photons. MCNP is a general purpose Monte Carlo code that can be used for electron, photon and coupled photon-electron transport. In this study the MCNP4A, 4B and 4C have been compared when calculating electron beam doses in water. For simulating, the geometry and other parameters were the same for three codes. By choosing two energy indexing algorithm [ITS and MCNP], absorbed doses were scored in water. 10[6] Particles were followed in these three cases. MCNP4C and 4B gave different results compared to 4A when the ITS algorithm was used in 4B and 4C versions. There was a good agreement between versions 4B and 4C. For the energy spectrum, there were significant differences between these three versions in two planes. Because of new improvements in electron transport in 4C, this version is reliable for electron transport and also requires a shorter time than the two previous versions. These results, in addition to the practical measurements acquired with MCNP4B by other investigators, suggest that in electron transport the user should use the ITS indexing energy algorithm