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

Abstract

Previous studies have shown that 4-(2 ' -methoxyphenyl)-1 [2 '-(N-2 "- pyridinyl)-p- [F-18]fluorobenzamido]ethylpiperazine ([F-18]MPPF) binds with high selectivity to serotonin (5-HT1A) 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 [18F]MPPF. Both the Logan analysis method with cerebellar input and the simplified reference tissue method can be applied clinically