Figure 3.

Surviving fraction of confluent cultures of A549 cells where 1–25 cells were irradiated with 1, 5, and 10 carbon ions. The surviving fraction of the non‐irradiated A549 control was normalized as 1.0 (asterisks: P < 0.05 compared with non‐irradiated A549 control). The data are plotted with the means and standard errors of more than three independent experiments. The reduction rates that were statistically significant were as follows: 9% (P = 0.014) for the 5 cells irradiated by 5 ions/cell; 8% (P = 0.021) for the 5 cells irradiated by 10 ions/cell; 12% (P = 0.002) for the 25 cells irradiated by 5 ions/cell; and 14% (P = 0.033) for the 25 cells irradiated by 10 ions/cell (asterisks: P < 0.05 compared with non‐irradiated A549 control).