The recent clinical authorization of amyloid Positon Emission Tomography (PET) in France represents a crucial step for the nuclear medicine community involved in the diagnosis of Alzheimer's disease (AD).

The recent clinical authorization of amyloid Positon Emission Tomography (PET) in France represents a crucial step for the nuclear medicine community involved in the diagnosis of Alzheimer's disease (AD). At the era of Amyloid, Tau, Neurodegeneration (ATN) biomarkers, amyloid PET fills a need in patients with an atypical or mixed clinical presentation, in particular young patients (< 65 years old), when the lumbar puncture is contraindicated or not feasible for technical reasons. Importantly, a negative amyloid PET scan discards the diagnosis of AD. Furthermore, early phase imaging of amyloid PET allows to estimate the perfusion neuronal state, increasing the diagnostic value of such PET radiotracer. Its role could be further developed in routine care for the selection and monitoring of promising disease modifiers therapies.

Inclusion Criteria:

• Patients aged = or > 18 years
• Patients who have had an amyloid PET scan with a PET request form including the indications for the examination
• Patient informed via a newsletter and non-opposition to the use of their data for research purposes (research objectives clearly explained in the letters)

Exclusion Criteria:

• Patient opposition to the use of their data for this research

All patients who had a flutemetamol amyloid PET scan with a PET request form including the indications for the examination and who received the information letter on the objectives of the research and who did not object to the use of their data.