5. Based on Treatment Planning Imaging (MR and/or CT) done on the day of treatment: -Brain edema and/or mass effect that causes midline shift or shift in wall of ventricle of more than 5 mm. -Lesions localized in the brain stem or the posterior fossa. -Lesions less than 5mm from primary branches of cerebral vessels, venous sinus, hypophysis or cranial nerves. -Evidence of recent (<2 weeks) hemorrhage.