Tau positron emission tomography radiolabelled probes such as T807, THK-5117, and PBB3 can image the pathology of the disease in vivo. The 18F-labeled tau imaging agents 18F-THK-5351, 18F-T807 (18F-AV-1451), and 18F-RO6958948 are presently under evaluation in clinical studies and clinical trials worldwide.