This is a single-center exploratory observational clinical study combining cross sectional and longitudinal aspects. It contains 18F-AV-1451-PET as an intervention. The primary objective is to measure tau deposition with 18-F-AV1451-PET based on voxel wise or volume based quantitative assessments and to study the effects of Tau deposition on the organism by identification of factors correlating to the measured tau deposition. Study participants will be followed for up to 5 years.