Amyloid PET. PET imaging of Aβ aggregates (including 18F-flutemetamol PET) has been approved for use in clinical routine practice in Sweden. In the present study, 18F-flutemetamol PET will be done in non-demented cases only. In the cases with dementia CSF Aβ will be enough to determine the presence or absence of brain amyloid pathology. However, in the cognitively healthy cases and in the patients with SCD or MCI we are interested in following the spread of amyloid pathology throughout the brain during the preclinical stages of AD and the spatial relationship to tau pathology. Therefore, Amyloid PET will be done according to clinical routine procedures in addition to CSF Aβ measurements in these groups. In the present study Amyloid PET will be performed using 18F-flutemetamol. GE Healthcare will provide the precursor for 18F-flutemetamol. A 20 min scan will be performed between 90-110 min post injection of 18F-flutemetamol.