Investigation of the direct DNA damages irradiated byprotons of different energies using geant4-DNAtoolkit

Background: the total yields of direct single-strand breaks (ssbs) and double-strand breaks (dsbs) in proton energies varying from 0.1 to 40 mev werecalculated. while other studies in this field have not used protons with energyless than 0.5 mev, our results show interesting and complicated behavior ofthese protons. materials and methods: the simulation has been done usingthe geant4-dna toolkit. an atomic model of dna geometry was simulated.simulations were performed with a source in the z-axis direction at the cellnucleus entrance with protons at energies of 0.1-1 mev in 0.1 mev steps, 5mev, and 10-40 mev in 10 mev steps. results: the calculated ssb yieldsdecreased from 60.08 (gbpgy)−1 for 0.1 mev proton energy to 49.52 (gbpgy)−1 for 0.5 mev proton energy, and then it increased to 54.35 (gbpgy)−1 in 40mev. the dsb yields decreased from 4.32 (gbpgy)−1 for 0.1 mev protonenergy to 1.03 (gbpgy)−1 for 40-mev protons. the dsb yields for energies lessthan 0.5 mev was about 56%, and for the other energy levels, it was 44%. asfor ssb yields, 35% of the breaks arose from protons with an energy of fewerthan 0.5 mev and 65% from higher energies. conclusion: it was found thatthe proton ranges with an energy less than 0.5 mev are smaller than the cellsize (10 μm), and 100% of the energy is deposited in the cell region. thenprotons with these energies are the best choice to increase the number ofdsbs