A novel positron emission tomography (PET) radiotracer has been shown to effectively measure increases in brain tau—a distinguishing characteristic of Alzheimer’s disease—before any symptoms of the disease are observed. With the potential to measure increases in tau over a long period of time, this tracer offers an important tool to assess the effectiveness of Alzheimer’s disease treatments in clinical trials. This research was presented at the Society of Nuclear Medicine and Molecular Imaging 2021 Annual Meeting.