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.

Inclusion Criteria:

• Alzheimer's Disease patients - 50-85 years, mild to moderate AD: MMSE ≥16 and ≤ 26, clinical progression of AD over 12 months.
• Healthy volunteers: - 50-75 years
• BMI 18 and 30 m2/kg
• Clinically normal physical findings including supine blood pressure and pulse rate.

Exclusion Criteria:

• Alzheimer's Disease patients - Clinically significant illness the 2 weeks prior to the administration of the PET ligand
• Significant cerebrovascular disease or depression, central nervous system infarct or infection or lesions
• Administration of any investigational product within 3 months prior to study and/or PET measurements for scientific purposes within the last 12 months.
• Healthy volunteers - clinically significant illness within 2 weeks before administration of PET ligand, history of psychiatric or somatic disease/condition that may interfere, first degree relative with dementia. Obvious deterioration of memory functions.