In vivo imaging of the 18-kDa translocator protein (TSPO) with [18F]FEDAA1106 and PET does not show increased binding in Alzheimer’s disease patients

Purpose Imaging the 18-kDa translocator protein (TSPO) is considered a potential tool for in vivo evaluation of microglial activation and neuroinflammation in the early stages of Alzheimer’s disease (AD). ((R)-1-(2-chlorophenyl)-N-[11C]-methyl-N-(1-methylpropyl)-3-isoquinoline caboxamide ([11C]-(R)-PK11195) has been widely used for PET imaging of TSPO and, despite its low specific-to-nondisplaceable binding ratio, increased TSPO binding has been shown in AD patients. The high-affinity radioligand N-(5-fluoro-2-phenoxyphenyl)-N-(2-[18F]fluoroethyl-5-methoxybenzyl)acetamide ([18F]FEDAA1106) has been developed as a potential in vivo imaging tool for better quantification of TSPO binding. The aim of this study was to quantify in vivo binding of [18F]FEDAA1106 to TSPO in control subjects and AD patients.