Even in this time of uncertainty, Mayo Clinic is a place for hope and healing — and we're committed to delivering the care you need. With options for face-to-face, virtual visits or phone appointments in adherence with federal and state executive orders and guidance. Geoffrey B. Johnson, M.D., Ph.D., is a nuclear medicine specialist and radiologist at Mayo Clinic's campus in Rochester, Minnesota. Dr. Johnson is Chair, Division of Nuclear Medicine, Department of Radiology. His focus is neuroendocrine tumors, including adrenal cancer, carcinoid tumors, merkel cell carcinoma, pancreatic neuroendocrine tumors, paraganglioma and pheochromocytoma. U.S. News & World Report consistently ranks Mayo Clinic among the top hospitals for cancer in the nation.