Taking EGSnrc to new lows: Development of egs++ lattice geometry and testing with microscopic
Abstract
Purpose: This work introduces a new lattice geometry library, egslattice, into the EGSnrc Monte Carlo code, which can be used for both modeling very large (previously unfeasible) quantities of geometries and establishing recursive boundary conditions. The reliability of egslattice, as well as EGSnrc in general, is cross-validated and tested. Methods: New Bravais, cubic, and hexagonal lattice geometries are defined in egslattice and their transport algorithms are described. Simulations of cells and Gold NanoParticle (GNP) containing cavities are implemented to compare to published Geant4-DNA and PENELOPE results. Recursive boundary conditions, implemented through a cubic lattice, are used to perform electron Fano cavity tests. Results: Lattices are successfully implemented in EGSnrc. EGSnrc calculated doses to cell cytoplasm and nucleus when irradiated by an internal electron source with a median difference of 0.6% compared to Geant4-DNA. EGSnrc calculated the ratio of dose to a microscopic cavity containing GNPs over dose to a cavity containing a homogeneous mixture of gold, and results generally agree (within 1%) with PENELOPE. The Fano test is passed (sub-0.1%) for all energies/ cells considered. Additionally, the recursive boundary conditions used for the Fano test provided a factor of over a million increase in efficiency in some cases. Conclusions: The egslattice geometry library, currently available as a pull request on the EGSnrc GitHub develop branch, is now freely accessible as open-source code. Lattice geometry implementations cross-validated with independent simulations in other MC codes and verified with the electron Fano cavity test demonstrate not only the reliability of egslattice, but, by extension, EGSnrc's ability to simulate transport in nanometer geometries and score in microscopic cavities.