Head-to-head comparison of 11C-PBR28 and 11C-ER176 for quantification of the translocator protein in the human brain

Paolo Zanotti-Fregonara, Belen Pascual, Mattia Veronese, Meixiang Yu, David Beers, Stanley H. Appel, Joseph C. Masdeu

Research output: Contribution to journalArticlepeer-review

30 Scopus citations


Introduction: 11C-ER176 is a new PET tracer to quantify the translocator protein (TSPO), a biomarker for inflammation. The aim of this study was to perform a head-to-head comparison between 11C-ER176 and the widely used 11C-PBR28. Methods: Seven healthy volunteers had a 90-min PET scan and metabolite-corrected arterial input function with 11C-PBR28 in the morning and 11C-ER176 in the afternoon. Binding was quantified at the regional level in terms of VT with a two-tissue compartmental model. By using VND values from the literature obtained with pharmacological blockade, we derived the binding potential BPND for both tracers. Results: 11C-ER176 was more stable in arterial blood than 11C-PBR28 (the percentages of unmetabolized parent in plasma at 90 min were 29.0 ± 8.3% and 8.8 ± 2.9% respectively). The brain time–activity curves for both tracers were well fitted by the two-tissue model, but 11C-ER176 had higher VT values than 11C-PBR28 (5.74 ± 1.54 vs 4.43 ± 1.99 ml/cm3) and a lower coefficient of variation. The BPND of 11C-ER176 was more than 4 times larger than that of 11C-PBR28 for high-affinity binders, and more than 9 times larger for mixed-affinity binders. Conclusion: 11C-ER176 displays a higher binding potential and a smaller variability of VT values. Thanks to these characteristics, clinical studies performed with 11C-ER176 are expected to have higher statistical power and thus require fewer subjects.

Original languageEnglish (US)
Pages (from-to)1822-1829
Number of pages8
JournalEuropean Journal of Nuclear Medicine and Molecular Imaging
Issue number9
StatePublished - Aug 1 2019


  • C-ER176
  • C-PBR28
  • PET
  • TSPO

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging


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