Practice Effects and Amyloid Imaging Using 18F-PIB or Flutemetamol PET and FDG-PET

The overall objective of this companion study project is to study the biodistribution and binding of 18F-Flutemetamol using PET imaging in community-dwelling functionally intact elderly subjects. Understanding the biodistribution and binding of this radiopharmaceutical in normal patients with various levels of potential for cognitive decline will help determine its appropriate role as a disease biomarker and aid in the interpretation of images produced with this agent. Comparison with FDG-PET is essential to correlate metabolic changes and for anatomic co-registration of 18F-PIB images necessary for group analysis. We will use 18F-Flutemetamol and FDG-PET to compare subjects with low and high practice effects with the following aims and hypotheses: Specific Aim 1: Examine the relationship between practice effects and amyloid burden in a community sample. Specific Aim 2: Determine whether FDG-PET or 18F-Flutemetamol better distinguish individuals with high and low practice effects. Hypothesis 1: Practice effects will be negatively correlated with amyloid deposition, so that higher levels of practice effects (i.e., better repeat testing) will be associated with lower levels of brain amyloid deposition and lower levels of practice effects (i.e., poorer repeat testing) will be associated with greater levels of brain amyloid and these two groups are more clearly distinguishable with 18F-PIB than FDG-PET. Hypothesis 2: Patients with increased amyloid deposition shown with 18F-PIB will have an FDG-PET scan with more pronounced temporal and parietal hypometabolism as noted on visual review of images and on statistical image analysis.