The study is carried out in order to investigate if [18F]AZD4694, compared to [11C]AZD2184, is a suitable PET ligand for in vivo imaging of Aβ amyloid depositions in the human brain. In the study the two PET ligands will be examined in both healthy volunteers and patients with Alzheimer's Disease. A whole body dosimetry scanning will be performed in 6 healthy volunteers to obtain human data to estimate a safe dose.