The purpose of this study is to get information regarding the usefulness and accuracy of this new magnetic resonance imaging (MRI) technique - termed arterial spin labeling (ASL) - in the diagnosis of pediatric brain tumors.

The purpose of this study is to get information regarding the usefulness and accuracy of this new MRI technique - termed arterial spin labeling (ASL) - in the diagnosis of pediatric brain tumors. This technique can non-invasively measure the blood flow to the brain during MRI examination. Because aggressive brain tumors require new blood vessels and a high level of blood supply to support its growth, we believe the tumor blood flow measured using ASL is a reliable indicator of tumor grade. This information may be useful for doctors to make treatment decisions and to monitor patients' response to treatment.

Inclusion Criteria:

• Age 0-18 years
• Primary brain tumor (newly diagnosed or recurrent) with measurable disease (at least 1cm2)

Exclusion Criteria:

• Patients with cardiac pacemaker or ferrous metal foreign bodies
• Patients with medical problems contradictive to receiving MRI scans.
• Patients requiring general anesthesia or sedation for their MRI scan.
• Patients with a history of cerebrovascular disorders (stroke, moya moya) that may alter cerebral perfusion.

Patients between 0-18 years who are diagnosed with primary brain tumor, undergoing MRI for clinical purpose are eligible for the study.