Intraoperative magnetic resonance imaging has been applied to a number of neurosurgical disease processes since the late 1990?s. The ability to visualize the operative site in near-real time has added a significant degree of safety to the treatment of lesions such as a cystic craniopharyngioma which can be located in regions of the brain where an untoward consequence can result in significant neurological morbidity. Previous surgical techniques, although often successful, did not allow the neurosurgeon to directly visualize whether the goals of surgery had been met or whether there was an inadvertent complication associated with the surgical approach until after the event had occurred. The safe and accurate instillation of radioactive phosphorus into this cystic tumor resulted in clinical improvement and the maintenance of normal pituitary function for this patient. The extreme accuracy and safety of this surgical technique is demonstrated by the imaging examples provided.

Key words: Craniopharyngioma, intracavitary irradiation, phosphorus, MRI, interventional MRI.