Comparative Monte Carlo simulation study of helium-induced DNA damage versus proton

Helium ions are thought to be effective for radiotherapy, and characterization of physical quantities related to cellular effects of helium ions are important in order to develop and improve treatment planning systems for helium ions. In this study, Geant4-DNA was used to obtain the physical energy deposit and OH reaction sites to feed the density-based spatial clustering of applications with noise (DBSCAN) and obtain the quantities related with DNA strand breaks. The results are compared to other calculations and show that with proper choice of variables, DBSCAN could be used to calculate the DNA damage. The helium DSB (double strand break) yields with chemical processes increased from 11.48 ${\left(GyGbp\right)}^{-1}$ with the LET of 56.3 keV/μm to 49.32 ${\left(GyGbp\right)}^{-1}$ at 219.2 keV/μm. The helium SSB (single strand break) yields with chemical processes decreased from 255.36 ${\left(GyGbp\right)}^{-1}$ with the LET of 56.3 keV/μm to 161.28 ${\left(GyGbp\right)}^{-1}$ at 219.2 keV/μm. SSB and DSB counts induced by helium particles incident on the lung adenocarcinoma cell nucleus increased by about 90 % and 200 % compared with those without chemical processes.