Gross Tumor Volume (GTV) was defined as the arterial enhancing
lesions with wash-out on the delayed phase. Delineation was
facilitated by image fusion approach, using pre-treatment MRI.
The Clinical Target Volume (CTV) was obtained adding 5–10 mm
isotropic margins to the GTV. The Planning Target Volume (PTV)
corresponds to the CTV with 2–4 mm isotropic margins. CTV and
PTV margins were chosen mostly according to the size and visibility
of the target on the planning CT.