Changes in LET with the penetration depth in liquid water at 25°C for carbon ions at the three energies considered in this study, as obtained using the SRIM software (43). Total ions calculated = 1,000. The arrows on the left side show the entry LET of the ions: ~330, 11.3 and 10 keV/μm, corresponding to the incident ion energies of 4.1, 290 and 400 MeV per nucleon, respectively.