Improved modeling of multiple scattering in the Voxel Monte Carlo model.

The implementation of an improved model for multiple scattering into the-Voxel Monte Carlo (VMC) algorithm for fast electron dose calculation in radiation therapy is presented. The model takes into account path-length corrections (PLC) and lateral displacement in the individual electron steps. The extraction of the scattering power from the available computed-tomography images is discussed. It is shown that with the improved modeling of multiple electron scattering, the VMC algorithm is comparable in accuracy with PRESTA, the electron transport algorithm of EGS4. The problem of double counting of contributions from atomic electrons to the scattering power is considered and a simple solution is found.