Eligible patients will have histologically confirmed cancer and MRI evidence of metastatic disease within the brain. Patients will be eligible for the trial if intracranial radiosurgery has been recommended for treatment of brain metastases. Patients will be excluded if they have an extremely radiosensitive tumor (leukemia, lymphoma), a radiosensitivity syndrome, a resection of a brain metastasis, or cannot tolerate the MRI or placement of a stereotactic head frame. All patients must sign informed consent.