 Patients will undergo standard pre-diagnostic imaging of the sites of disease using standard MRI techniques. If disease is suspected in both the brain and spine, then both imaging modalities should be obtained. This imaging should be obtained no more than 21 days before surgical resection. As close as possible to the completion of the MRI scans, patients will undergo 18F-FLT imaging using a single administration of tracer, and PET image acquisition at four different time points baseline, 1 hr post injection, 2 hrs post injection and 4-6 hours post injection. A whole body PET scan top of the head to mid thigh will be performed immediately after injection PET acquisition 1. These data will be acquired with a 2 minute emission and a 2 minute transmission scan at each bed position. Following this acquisition, the subject will empty his or her bladder. At 45 minutes post-injection, a brain andor spine body PET scan will be acquired with a 10 min emission scan and a 5 min transmission scan PET acquisition 2. This scan will include all areas of suspected tumor brain, spine, or brain and spine. Following PET acquisition 2, a whole body PET scan will be acquired according to the same protocol as above PET acquisition 3. If possible, a final whole body scan will be acquired 4-6 h post-injection PET acquisition 4. All PET acquisitions will be acquired in 3D mode and reconstructed with the FORE re-binned OSEM algorithm with measured attenuation correction. Blood samples will be obtained at the completion of each whole body scan. Patients will receive the dose of 18F-FLT through a fresh intravenous catheter as per standard PET procedures. Patients will then undergo maximal surgical resection. Pieces from different areas of the tumor will be marked for correlation to imaging studies when possible. Tumor samples will undergo standard immunohistochemical analysis for cellular activation including mitotic index and MIB-1 proliferation staining. 