Figure 1.

Illustration of the different treatment techniques, shown on a representative booster plan for the gross tumor volume (red) in the paranasal sinus region. The conventional treatment method ((A) volumetric modulated arc therapy) shows a higher dose delivered to organs at risk, e.g., the chiasm (purple), both optic nerves (yellow and blue), and the brainstem (green). The dose distribution of the pencil beam scanning technique with (B) protons and (C) C-ions show better sparing of the organs at risk, especially visible in the right optical nerve and brainstem, while achieving a comparable tumor coverage.