Figure 1

Left: Schematic survival probabilities for the three cases depicted on the right. (a) Cell killing as a single rate process with transition rate from alive (A) to dead (D) \(\alpha\). (b) Two-step cell killing process in the LQ-model for radiation. A cell transits from the alive state (A) to the dead state (D) through two possible paths: \(\alpha\) for direct killing (a single hit suffices to kill), and \(\beta\) for indirect killing (when two hits are required to kill). (c) Combined HT+RT: HT-induced damage elevates cells from state (A) to an activated state (\(A^\prime\)), effectively reducing the \(\alpha / \beta\) ratio. Since \(\beta\) is more efficiently reduced, the direct path \(\alpha\) dominates the killing process and consequently reduces the survival probability.