• Tumor location: Location of the tumor in critical brain areas (midline, brain stem, cerebrum: motor center, speech center, vision center) where conventional neurologic excision of the tumor is too risky or even impossible to perform.
• Tumor borders: Tumor well delineated on the MRI images
• Tumor size: Maximum tumor diameter 30 to 35mm

Brachytherapy may still come into play even if the tumor has already been treated with another radiation modality.