Comparability of [18F]THK5317 and [11C]PIB blood flow proxy images with [18F]FDG positron emission tomography in Alzheimer's disease

Abstract

For amyloid positron emission tomography tracers, the simplified reference tissue model derived ratio of influx rate in target relative to reference region (R 1) has been shown to serve as a marker of brain perfusion, and, due to the strong coupling between perfusion and metabolism, as a proxy for glucose metabolism. In the present study, 11 prodromal Alzheimer's disease and nine Alzheimer's disease dementia patients underwent [18F]THK5317, carbon-11 Pittsburgh Compound-B ([11C]PIB), and 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG) positron emission tomography to assess the possible use of early-phase [18F]THK5317 and R 1 as proxies for brain perfusion, and thus, for glucose metabolism. Discriminative performance (prodromal vs Alzheimer's disease dementia) of [18F]THK5317 (early-phase SUVr and R 1) was compared with that of [11C]PIB (early-phase SUVr and R 1) and [18F]FDG. Strong positive correlations were found between [18F]THK5317 (early-phase, R 1) and [18F]FDG, particularly in frontal and temporoparietal regions. Differences in correlations between early-phase and R 1 ([18F]THK5317 and [11C]PIB) and [18F]FDG, were not statistically significant, nor were differences in area under the curve values in the discriminative analysis. Our findings suggest that early-phase [18F]THK5317 and R 1 provide information on brain perfusion, closely related to glucose metabolism. As such, a single positron emission tomography study with [18F]THK5317 may provide information about both tau pathology and brain perfusion in Alzheimer's disease, with potential clinical applications.