Figure 1: (a) 3D-CRT, (b) IMRT, and (c) Carbon ion radiotherapy. Representative axial dose distribution for three-dimensional conformal radiation therapy (3D-CRT) plan (4 ports), intensity-modulated radiation therapy (IMRT) plan (9 ports), and carbon ion radiotherapy (4 ports) plan. The cyan-, orange-, and red-colors show 50%, 80%, and 95% isodose lines, respectively. The dark blue-, green-, and yellow-colors show the target volume, optic nerves, and brain stem, respectively.