Fig. 4

RBE for human normal cells irradiated with carbon ions: \(\text {RBE}_{\alpha } = \alpha _{\text{ion}}/\alpha _{\text{X}}\) (left panel) and RBE(2 Gy, \(\gamma\)) (right panel). Solid lines show the RBE values calculated by means of the MSA. The \(\text {RBE}_{\alpha }\) curves denoted as (1), (2), (3) correspond to experimental data (shown by symbols) from Belli et al. (2008), Suzuki et al. (2000) and Tsuruoka et al. (2005), respectively