The investigators plan to study high dose, single treatment radiation, using a plastic mask instead of a head frame that pins into a patient's skull. The investigators need to (1) quantify set-up accuracy and patient motion during radiation treatment and (2) ensure that without the head frame the tumour control rate and risk of complications are similar to our previous experience using the head frame.

Inclusion Criteria:

• Patients with brain metastases from a biopsy-proven primary extra-cranial tumor site, excluding lymphoma, germ cell, and small cell lung carcinoma histologies.
• One to four metastases, and all lesions < 3.5 cm in maximal diameter. Extracranial metastases is of minimal volume or stable with treatment. - Karnofsky performance status ≥ 70

Exclusion Criteria:

• None of the lesions is abutting or within critical neurological structures: *brainstem

  • optic chiasm
  • eye, and optic nerve.

• The clearance between metastatic lesions and all critical structures must be at least 2 mm.

• Patients must not have leptomeningeal disease.

• Contraindications to imaging or radiation (e.g. pregnancy, elevated serum creatinine, allergy to contrast agents, severe claustrophobia, metal particles in the eye).