INPUT FUNCTIONS FOR 6-[FLUORINE-18]FLUORODOPA QUANTITATION IN PARKINSONISM - COMPARATIVE-STUDIES AND CLINICAL CORRELATIONS

PET has been used to quantify striatal 6-[F-18]fluoro-L-dopa (FDOPA) u ptake as a measure of presynaptic dopaminergic function. Striatal FDOP A uptake rate constants (CC) can be calculated using dynamic PET imagi ng with measurements of the plasma FDOPA input function determined eit her directly or by several estimation procedures. Methods: We assessed the comparative clinical utility of these methods by calculating the striato-occipital ratio (SOR) and striatal K-i values in 12 patients w ith mild to moderate PD and 12 age-matched normal volunteers. The plas ma FDOPA time-activity curve (K-i(FD)); the plasma F-18 time-activity curve (K-i(P)); the occipital time-activity curve (K-i(OCC)); and a si mplified population-derived FDOPA input function (K-i(EFD)) were used to calculate striatal K-i. Results: Mean values for all striatal K-i e stimates and SOR were significantly lower in the PD group. Although al l measured parameters discriminated PD patients from normals, K-i(FD) and K-i(EFD) provided the best between-group separation. K-i(FD), K-i( EFD) and K-i(OCC) measures correlated significantly with quantitative disease severity ratings, although K:D predicted quantitative clinical disability most accurately. Conclusion: These results suggest that K- i(FD) may be an optimal marker of the parkinsonian disease process. K- i(EFD) may be a useful alternative to K-i(FD) for most clinical resear ch applications.