18F-Fluorodopamine PET Studies of Neuroblastoma and Pheochromocytoma

PET (positron emission tomography) scans combined with a radioactive tracer will be used to identify and analyze tumors. Currently, the most common tracer used to analyze neuroblastoma tumors is called 123I-mIBG. However, the picture it provides is not always clear enough to see the very small areas of the disease. 18F-DA (18F-fluorodopamine) has been shown to be safe and more effective than 123I-mIBG in analyzing the tumor pheochromocytoma, which is closely related to neuroblastoma. With this research study, the investigators plan to meet the following goals: * Investigate to see if 18F-DA is safe to administer to pediatric patients with known or suspected neuroblastoma or pheochromocytoma * Examine where in the body 18F-DA goes. * Obtain information comparing 18F-DA to 123I-mIBG to see if 18F-DA could replace 123I-mIBG in the future. About 20 people, with known or suspected neuroblastoma or pheochromocytoma, will take part in this Pilot study at St. Jude.