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

Eur J Nucl Med Mol Imaging. 2013 Jun;40(6):921-31. doi: 10.1007/s00259-013-2359-1. Epub 2013 Feb 22.


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-[(11)C]-methyl-N-(1-methylpropyl)-3-isoquinoline caboxamide ([(11)C]-(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-[(18)F]fluoroethyl-5-methoxybenzyl)acetamide ([(18)F]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 [(18)F]FEDAA1106 to TSPO in control subjects and AD patients.

Methods: Seven controls (five men, two women, age 68±3 years, MMSE score 29±1) and nine AD patients (six men, three women, age 69±4 years, MMSE score 25±3) were studied with [(18)F]FEDAA1106. PET measurements were performed on an ECAT EXACT HR system (Siemens Medical Solutions) in two 60-min dynamic PET sessions with a 30-min interval between sessions. Arterial blood radioactivity was measured using an automated blood sampling system for the first 5 min and using manually drawn samples thereafter. Quantification was performed using both kinetic analysis based on a two-tissue compartment model and Logan graphical analysis. Outcome measures were total distribution volume (V T) and binding potential (BP(ND)=k3/k4). An estimate of nondisplaceable distribution volume was obtained with the Logan graphical analysis using the first 15 min of PET measurements (V(ND 1-15 min)). Binding potential (BP(ND)) was also calculated as: V(T)/V(ND 1-15 min) - 1.

Results: No statistically significant differences in V(T), k3/k4 or BP(ND) were observed between controls and AD patients.

Conclusion: This study suggests that TSPO imaging with [(18)F]FEDAA1106 does not enable the detection of microglial activation in AD.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetamides / pharmacology*
  • Aged
  • Alzheimer Disease / diagnostic imaging*
  • Alzheimer Disease / pathology*
  • Automation
  • Brain Mapping
  • Female
  • Fluorodeoxyglucose F18 / pharmacology*
  • Humans
  • Image Processing, Computer-Assisted
  • Magnetic Resonance Imaging
  • Male
  • Positron-Emission Tomography*
  • Receptors, GABA / metabolism*
  • Time Factors
  • Tissue Distribution
  • Treatment Outcome


  • Acetamides
  • N-(5-fluoro-2-phenoxyphenyl)-N-(2-fluoroethyl-5-methoxybenzyl)acetamide
  • Receptors, GABA
  • TSPO protein, human
  • Fluorodeoxyglucose F18