[18F]-Flutemetamol Uptake in Cortex and White Matter: Comparison with Cerebrospinal Fluid Biomarkers and [18F]-Fludeoxyglucose.

Flutemetamol (F-18-Flut) is an [F-18]-labelled amyloid PET tracer with increasing availability. The main objectives of this study were to investigate 1) cerebrospinal fluid (CSF) A beta 1-42 (A beta(42)) concentrations associated with regional F-18-Flut uptake, 2) associations between cortical F-18-Flut and [F-18]-fludeoxyglucose (F-18-FDG)-PET, and 3) the potential use of F-18-Flut in WM pathology. Cognitively impaired, nondemented subjects were recruited (n = 44). CSF was drawn, and F-18-Flut-PET, F-18-FDG-PET, and MRI performed. Our main findings were: 1) Different Alzheimer's disease predilection areas showed increased F-18-Flut retention at different CSF A beta(42) concentrations (posterior regions were involved at higher concentrations). 2) There were strong negative correlations between regional cortical F-18-Flut and F-18-FDG uptake. 3) Increased F-18-Flut uptake were observed in multiple subcortical regions in amyloid positive subjects, including investigated reference regions. However, WM hyperintensity F-18-Flut standardized uptake value ratios (SUVr) were not significantly different, thus we cannot definitely conclude that the higher uptake in F-18-Flut(+) is due to amyloid deposition. In conclusion, our findings support clinical use of CSF A beta(42), putatively relate decreasing CSF A beta(42) concentrations to a sequence of regional amyloid deposition, and associate amyloid pathology to cortical hypometabolism. However, we cannot conclude that F-18-Flut-PET is a suitable marker for WM pathology due to high aberrant WM uptake.