On the quantification of [18F]MPPF binding to 5-HT1A receptors in the human brain.

Previous studies have shown that 4-(2'-methoxyphenyl)-1-2'-(N-2"-pyridinyl)-p-(18)F]fluorobenzamido]ethylpiperazine ((18)F]MPPF) binds with high selectivity to serotonin (5-HT(1A)) receptors in man. However, in these studies, the calculation of the binding potential (BP, which equals receptor density divided by equilibrium dissociation constant) used a metabolite-corrected arterial input. The aim of this study was to determine whether metabolite correction and arterial sampling are essential for the assessment of BP. METHODS: Five analytic methods using full datasets obtained from 6 healthy volunteers were compared. In addition, the clinical applicability of these methods was appraised. Three methods were based on Logan analysis of the dynamic PET data using metabolite-corrected and uncorrected arterial plasma input and cerebellar input. The other 2 methods consisted of a simplified reference tissue model and standard compartmental modeling. RESULTS: A high correlation was found between BP calculated with Logan analysis using the metabolite-corrected plasma input (used as the reference method for this study) and Logan analysis using either the uncorrected arterial plasma input (r(2) = 0.95, slope = 0.85) or cerebellar input (r(2) = 0.98, slope = 0.91). A high correlation was also found between our reference method and the simplified reference tissue model (r(2) = 0.94, slope = 0.92). In contrast, a poor correlation was observed between our reference method and the standard compartmental model (r(2) = 0.45, slope = 1.59). CONCLUSION: These results indicate that neither metabolite analysis nor arterial sampling is necessary for clinical evaluation of BP in the human brain with (18)F]MPPF. Both the Logan analysis method with cerebellar input and the simplified reference tissue method can be applied clinically.