Fig. 3.
Head tilt simulations in the treatment planning system. Although a head‐tilting device was not used in the planned CT, the head tilt angle was set by measuring the gantry angle with the couch angle of 90°. For example, (a) the gantry angle of α° without the tilting device is equivalent to (b) the gantry angle of 0° with the tilting device of α°.