Gamma Knife radiosurgery is a non-invasive technique for the delivery of a single, high dose of radiation to an intra-cranial target. MRI has an established and central role in the treatment planning process and assessment of response to intracranial radiosurgery. Increasing the field strength of MRI from 1.5T to 3T promises to improve the signal, and in turn the quality of images. However, the technology also introduces new limitations, and the role and safety of 3T MRI in the management of patients receiving radiosurgery has not yet been reported. In this pilot study, we will explore the spatial integrity, and incremental image-guidance utility of 3T MRI in patients receiving radiosurgery. The preliminary data acquired in this study will be instrumental to the judicious design and conduct of subsequent definitive clinical trials. Up to fifty patients will be enrolled in this study.

Inclusion Criteria:

• Patients planned to receive Gamma Knife radiosurgery will be eligible for enrollment on this study.

Exclusion Criteria:

• Age<18
• Contra-indications to 3T MRI, such as implanted metal devices or shrapnel.

Patients who have consented to Gamma Knife radiosurgery.