Figure 2.

Dose distribution in optic pathways for each patient (Px); optic chiasma (a), ipsilateral optic nerve (b) and controlateral optic nerve (c) respectively. The dose difference in Gy between non coplanar field NCF and coplanar field CF (D NCF – D CF) is represented in terms of D1%, D2%, and D5% corresponding to the doses in 1, 2 and 5 % of the volumes respectively. This means that when the difference is negative, the dose to optic pathways is higher when using coplanar field technique.