The purpose of this study is to see how a new tracer named 18F-MFBG (Meta Fluorobenzyl Guanidine) behaves in the body after injection, how it spreads to all the organs and how it is removed from the body. We will also study how long 18F-MFBG lasts in the blood after administered. In addition we want to study if 18F-MFBG can show Neuroendocrine tumors on a PET-CT or PET MR scan.

Inclusion Criteria:

Phase I:

• Eligible patients include patients with histologically proven Neuroendocrine tumors (paraganglioma, PHEO, or well differentiated NET of the lung or GI system) or NB. Patients who have NB, the diagnosis must be in accordance with the International Criteria, i.e., either histopathology or bone marrow involvement. Patients must be ≥5 years of age and able to undergo PET scan without sedation
• All patients must have MIBG-avid disease and evaluable disease on MIBG scan at the time of enrollment onto the protocol.
• Performance status of ≥60 on Karnofsky scale for patients >16 years of age and >60 on Lansky scale for patients <16 years of age.
• Cardiac, pulmonary, gastrointestinal and neurologic toxicity should all be ≤grade 2.

Expansion Cohort:

• Patients with diagnosis of NB (in accordance with the International Criteria, i.e., either histopathology or bone marrow involvement)

• Patients must be able to undergo PET scan without sedation

• Patients must have prior MIBG-avid disease and evaluable disease on MIBG scan at the time of enrollment onto the protocol.

  • If MIBG scan is available within 4 weeks of MFBG, with no intervening treatment, MIBG scan will not be repeated.
  • If prior MIBG scan is available >4 weeks of MFBG, MIBG scan will be done within a week (prior or after) of MFBG.

• Performance status of ≥60 on Karnofsky scale for patients >16 years of age and >60 on Lansky scale for patients ≤16 years of age.

• Cardiac, pulmonary, gastrointestinal and neurologic toxicity should all be ≤grade 2.

• Patients with positive lesion detection by 18F-MFBG may be eligible for repeat imaging scan, at the discretion of PI or study investigator(s).

Exclusion Criteria:

• Major organ toxicity including cardiac, pulmonary, gastrointestinal and neurologic toxicity more than grade 2.
• Active serious infections not controlled by antibiotics.
• Inability or unwillingness to undergo PET scanning
• Uncontrolled intercurrent illness including, but not limited to, ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, or psychiatric illness/social situations that would limit compliance with study requirements.
• Women who are pregnant or breastfeeding.
• Patient has an active malignancy of metastatic potential other than the known NE tumor for the past 3 years.
• Patients should not have received chemotherapy or radiation therapy (localized radiation therapy is allowed to non-evaluable sites) between prior 123I-MIBG scan and 18F-MFBG administration.
• Patients requiring anesthesia, who are not already undergoing anesthesia for standard-of-care procedures.