Magnetic resonance imaging (MRI) is a diagnostic study that makes pictures of organs of the body using magnetic field and radio frequency pulses that can not be felt. The purpose of this study is to determine if new imaging methods can help tumor evaluation in the brain. The extra images will be obtained using diffusion and perfusion MRI techniques to assess early treatment response in patients with brain metastasis, and will be compared to methods currently being used.

Inclusion Criteria:

• Adults aged 18 and over.
• Patients/Subjects able to give informed consent
• Patients/Subjects whose weight does not exceed 275 lbs.
• Patient with metastatic brain tumors greater than or equal to 1.0 cm that will be treated with stereotactic radiosurgery and scheduled for an MRI scan as part of their routine care

Exclusion Criteria:

• Patients who are unwilling or unable to undergo MRI including patients with contra-indications to MRI such as the presence of cardiac pacemakers or non-compatible intracranial vascular clips.

The protocol investigators on the study will identify potential research participants from those patients who are scheduled for MRI examination as part of their routine clinical care.