Purpose: [(11)C]Carfentanil has been widely used in positron emission tomography (PET) studies for measuring micro-opioid receptor binding in humans, but the reproducibility of the binding parameter estimates is unknown.
Materials and methods: Eight healthy volunteers were scanned twice during the same day with [(11)C]carfentanil PET, and binding to receptors was assessed with both reference tissue and arterial plasma input-based models using region of interest (ROI) and voxel-based quantification.
Results: The two-tissue compartmental model distribution volume (V(T)) was highly reproducible as indicated by low variability (VAR < 6%) and high intraclass correlation coefficients (ICC > 0.93). BP(ND) (BP relative to the nondisplaceable tissue compartment) was also highly reproducible (VAR < 10%, ICC > 0.90) both at ROI- and voxel-level, and reference tissue-based models provided stable estimates after 40 min.
Conclusions: The reproducibility of [(11)C]carfentanil binding parameter estimates is excellent with outcome measures based on both arterial plasma and reference tissue input, and a scanning time of 40 min appears sufficient.