Evaluation of 18F-Fluciclovine Positron Emission Tomography - Magnetic Resonance Imaging (PET-MRI) in LGG

This study is using a specialized PET-MRI scan with a tracer called 18F-Fluciclovine to better monitor low-grade brain tumors (LGG) in children and young adults receiving treatment. The goal is to get clearer pictures of how these tumors respond over time. **You may be eligible if:** - You are between 1 and 21 years old - You have a confirmed or suspected low-grade brain tumor (WHO grade I or II) - Your tumor measures at least 1 cm x 1 cm on MRI - You are scheduled to receive treatment for your brain tumor - You are reasonably mobile and functional (Karnofsky or Lansky score of 50 or higher) **You may NOT be eligible if:** - You are pregnant - You weigh less than 8 kg (about 17 lbs) - You cannot avoid contact with a pregnant woman or infant for 12 hours after the scan - You have kidney problems - Your tumor is located in the spinal cord Talk to your doctor to see if this trial is right for you.