Estimation of produced oxygens in the track of heavy-ion using Geant4-DNA

Abstract

In X-ray irradiation, decreasing oxygen concentration correlates with a reduction in radiosensitivity. However, this effect is minimal in heavy ion irradiation due to the generation of oxygen along the ion track, called as the "oxygen in the heavy ion track hypothesis." We verified this hypothesis using Geant4-DNA by calculating oxygen generation and time change in distribution for 35 MeV/u and 200 MeV/u carbon ions, and 1 MeV electrons within a cell nucleus. The results showed, under hypoxic conditions (0% dissolved oxygen), the oxygen concentration increased to a maximum of 3.7% in a localized region around the track, persisting for about 100 ns after the penetration of 35 MeV/u carbon ion, while the increase for 1 MeV electrons was negligible. This finding supports the validity of the oxygen in the heavy ion track hypothesis.