The purpose of this research is to study 18F-L-Fluoro-DOPA (F-DOPA), a tracer, which is used to take pictures of the pancreas. This imaging test is called an F-DOPA PET scan. The F-DOPA tracer is used to highlight areas of the pancreas that make too much insulin on the PET scan images. The test includes a CT scan (computerized tomography) done at the same time on the same machine, to help define exactly where the highlighted area is located within the pancreas and determine the location of blood vessels and other vital structures.