18F-DOPA II - PET Imaging Optimization

This study is optimizing PET scan imaging using a tracer called 18F-DOPA, which helps visualize certain types of tumors and brain conditions by showing how dopamine is processed in the body. It is open to both children and adults depending on the condition being studied. **You may be eligible if...** - You are a child (under 18) with congenital hyperinsulinism (a rare condition causing too much insulin) or neuroblastoma (a childhood cancer) - You are a child or adult with a known or suspected neuroendocrine tumor - You are an adult (18+) with suspected Parkinson's disease or Lewy body dementia - You are a child or adult with a brain tumor **You may NOT be eligible if...** - You are unable to provide consent (or a guardian cannot) - You weigh more than 225 kg (scanner weight limit) - You are pregnant or breastfeeding Talk to your doctor to see if this trial is right for you.