Figure 1.

Exposed body volumes. Body volumes exposed to doses higher than x% of the prescribed dose (V_bodyx%) in robust IMPT-plans assuming set-up errors of 0, 2, and 5 mm around the target volume derived from the original PTV through isotropic shrinkage by set-up margins of 0, 2, and 5 mm, respectively, for 7 patients with recurrent head and neck carcinomas and evaluated isodose levels x between 20% and 95%. The ratios of V_bodyx% in the 0 and 5 mm IMPT-plans (IMPT_5mm and IMPT_0mm, respectively) over V_bodyx% exposed in the 2 mm IMPT-plan (IMPT_2mm) are displayed by red circles and green triangles, respectively. A significant decrease of −11.9 ± 0.8% in V_bodyx% in the robust IMPT_5mm-plan was obtained in comparison with V_bodyx% exposed in the robust IMPT_2mm-plan (p < 0.0001, F-Test). The respective increase in V_bodyx% in the IMPT_0mm-plan was 6.2 ± 0.9% (p < 0.0001, F-Test).