<qa>  What is the name of the new radiotracer that allows 10 to 15 minutes acquisition?Rationale: improving the early detection of AD at prodromal pre-dementia stages has become a major matter of concern. There is now an important body of literature stating that early isolated cognitive deficits Mild Cognitive Impairment-MCI- predict the risk of developing AD. Several biomarkers are now available : specific and sensitive neuropsychological assessments, morphometric evaluation of hippocampal volume and white matter changes by MRI, cerebrospinal fluid or plasma dosage of Ab fragments and tau proteins, assessment of brain glucose hypometabolism in temporo-parietal regions with PET F18FDG. However, PET imaging using labelled compounds specifically binding to APs has been suggested to improve the diagnostic reliability and to potentially help in shortening the delay until formal clinical diagnosis of AD. F18 AV45 is a new radiotracer which kinetics characteristics allows 10 to 15 minutes acquisition 50 to 60 minutes post injection. 