DETERMINATION OF UNCHANGED [F-18] DOPAMINE IN HUMAN AND NONHUMAN PRIMATE PLASMA DURING POSITRON EMISSION TOMOGRAPHY STUDIES - A NEW SOLID-PHASE EXTRACTION METHOD COMPARABLE TO RADIO-THIN-LAYER CHROMATOGRAPHY ANALYSIS

Routine determination of [F-18]DOPA and its metabolites in plasma is e ssential for assessment and quantification of presynaptic dopamine fun ction in vivo using a modeling approach with positron emission tomogra phy (PET). The determination of unchanged [F-18]DOPA from human and no n-human primate plasma using solid-phase extraction (SPE) with Sep-Pak cartridges during PET dopaminergic studies is described here. The res ults from the studies showed that this new approach in comparsion to a method such as thin-layer chromatography (TLC) possessed a simplicity , rapidity and accuracy as well as good correlation between the two te chniques (p<0.0001). A proposed procedure involving radio-analysis on alumina plates (Al2O3,) was also developed with an excellent correlati on compared to the conventional C-18 plates (r=0.96). Thus it could be concluded that the SPE on either C-18 or alumina cartridges (Waters) compared to radio-TLC analysis on C-18 and alumina systems, appears to be a useful analytical method suitable for correcting the input arter ial function in routine clinical PET neurotransmission studies.