Quantification of [123I]PE2I binding to dopamine transporters with SPET

The iodinated cocaine derivative [I-123]PE2I is a new selective ligand for in vivo studies of the dopamine transporter (DAT) with single-photon emission tomography (SPET). The aim of the present study was to describe a method for accurate quantification of binding data following a bolus injection of [I-123]PE2I. Six healthy subjects (age 51 +/- 24 years) underwent xenon-133 SPET for quantification of regional CBF and [I-123]PE2I SPET for quantification of DAT binding. rCBFs were within normal limits in all subjects. Fitting data to a two-tissue compartment model resulted in striatal K-1 values of 0.39 +/- 0.08 ml ml(-1) min(-1), equal to a first-pass extraction fraction of 0.72 +/- 0.13. Distribution volumes (DVs) were calculated using compartment analysis, area under the curve analysis and Logan analysis. Logan analysis is preferred since stable DV values were already obtained 120 min after [I-123]PE2I injection. Mean striatal DV was 37.9 +/- 9.6 ml ml(-1) and mean occipital cortex DV was 5.5 +/- 0.7 ml ml(-1). In the absence of local pathology in a reference tissue, Logan analysis without blood sampling is an attractive method for accurate quantification of striatal [I-123]PE2I binding. The distribution volume ratio (DVR) (6.6 +/- 1.4) was in good agreement with the DVR calculated with blood (6.7 +/- 1.4).