Fig. 1

Typical treatment plan and dose distribution for intensity-modulated carbon-ion radiotherapy delivered using the raster-scanning technique in a patient with stage rT3N0M0 nasopharyngeal carcinoma with recurrence at the base of the skull. Transverse, sagittal, and coronal views are provided. The red, orange, yellow, and blue shaded areas represent 95%, 85%, 70%, and 30% isodose lines; the red, green, and yellow lines represent gross tumor volume (GTV), GTV + 3 mm, and clinical target volume (CTV), respectively