Comparison of two methods for the analysis of [18F]6-fluoro-L-m-tyrosine PET data

PET and [18F]fluoro-L-m-tyrosine (FMT) have been used to quantify presynaptic striatal dopamine (DA) function in Parkinson disease (PD) and in primate models of PD. While dynamic imaging and a metabolite-corrected blood input function can be used to determine striatal FMT uptake rate constants (Ki), a simpler analytic approach using shorter imaging times is desirable for clinical studies. We compared the utility of using striatal Ki values versus striatal count ratios in two groups of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated monkeys. Striatal DA content was also measured in one of the groups to evaluate the relationship between the PET measures and an independent measure of striatal dopamine. Striatal Ki values were significantly correlated with striatal count ratios using the cerebellum as the denominator. Both Ki values and ratios were also correlated with striatal DA content. In addition, putamen-cerebellum ratios and putamen Ki values showed similar separation between baseline and post-MPTP values. These findings suggest that a simple ratio approach to analyzing FMT PET data may be a useful alternative to a kinetic approach especially for clinical applications.