Evaluating direct and indirect effects of low-energy electrons using Geant4-DNA

Abstract

Monte Carlo simulations can classify DNA damage into different types and predict the amount of energy deposited. Geant4-DNA was used to predict simple and complex DNA damage induced by irradiation of low-energy electrons at 0.1–50 keV. The number of molecules generated at different energy levels of radiation was analyzed after observing the gradual changes in the level of water radiolysis. A DNA model was used to categorize direct damage according to the location of strand breaks at the atomic level. The parameters of energy threshold (minimum amount of energy needed to break DNA strands) and 10 base pairs (maximum distance that separates two strand breaks) were set. All instances of water radiolysis including the main OH radical occurred most frequently at 1 keV followed by at 1.5 and 0.5 keV. Direct strand breaks most commonly occurred at 0.5 keV followed by at 0.3 keV. Finally, most of strand breaks occurred more frequently at 0.5 keV than at 0.3 keV. The computational measurement results for indirect and direct effects of irradiation depend on the type of simulation code and the DNA model used. Values used in Geant4 (physics list, chemical interaction time and energy threshold) may also influence the results.