Fig. 5

RBE at 10% cell survival for human normal tissue cells (left panel) and Chinese hamster V79 cells (right panel) irradiated with carbon ions. The results are obtained by means of Eq. (17). In the high-LET region the RBE becomes inversely proportional to LET, and the absolute values of RBE depend on the number of ions that traverse a cell nucleus. The values of \(N_{\text{ion}}\) corresponding to different segments of the calculated curve are indicated. Symbols depict experimental data from Suzuki et al. (1996, 2000), Tsuruoka et al. (2005), Belli et al. (2008), Cox and Masson (1979) and Hamada et al. (2006) (for human fibroblasts) and from Weyrather et al. (1999), Furusawa et al. (2000), Bird and Burki (1975) and Thacker et al. (1979) (for V79). The shaded area shows the variation of RBE with an account for statistical uncertainties in the number of ions traversing a cell nucleus and the LET (see the text for details)