Expanded Access [11C] Methionine PET Imaging

The participants are being asked to get this PET scan because the participants have or may have cancer in the central nervous system (head, neck, or spine), and the investigator and the patient's physician thinks that this scan may provide useful information for the participant's treatment. Primary Objective To provide expanded access to L-\[11C\]methionine as a positron-emitting tracer in children and young adults for the positron emission tomography (PET) imaging of neoplasms of the central nervous system (CNS) and head and neck to guide therapeutic management of disease.