Figure 1.

Illustration of mechanisms of radiation damage. Both photon and ion radiation (red wiggly and straight lines, respectively) may directly damage DNA (marked with yellow stars) or other parts of the cell, such as mitochondria (damage not shown), as well as ionize the medium, thereby producing radicals and other reactive species (represented here by the •OH radical) as well as secondary electrons, which can cause indirect damage after diffusion (red stars). Secondary electrons may also react with the medium to further increase the number of radicals. Reproduced with the permission from Sung et al., CA Cancer J Clin; published by Springer, 2016.