A single centre non-randomized, non-blinded phase III prospective cohort study of 18F-DOPA PET/CT imaging in specific patient populations: 1. Pediatric patients (less than 18 years old) with congenital hyperinsulinism. 2. Pediatric patients (less than 18 years old) with neuroblastoma. 3. Pediatric (less than 18 years old) or Adult patients (18 or older) with known or clinically suspected neuroendocrine tumor. 4. Adult patients (18 or older) with a clinical suspicion of Parkinson's disease or Lewy body dementia. 5. Pediatric (less than 18 years old) or Adult patients (18 or older) with brain tumors. Image optimization (the primary study objective) and gallbladder activity pattern (the secondary objective) will be evaluated.