4‐[18F]Fluoro‐L‐m‐Tyrosine: An L‐3,4‐Dihydroxyphenylalanine Analog for Probing Presynaptic Dopaminergic Function with Positron Emission Tomography

: 4‐[18F]Fluoro‐L‐m‐tyrosine (FMT), a biochemical probe of striatal dopaminergic function, has been synthesized as an L‐3,4‐di‐hydroxyphenylalanine analog for positron emission tomography. Biochemical characterization of this compound in the rat 30 min after intrajugular administration indicated that in the brain, selective decarboxylation occurred in the striatum, with the formation of 4‐fluoro‐3‐hydroxyphenylethylamine and its metabolites. Positron emission tomography analysis of brain tissue in monkeys (Macaca nemestrina) after intravenous injection of FMT revealed a true time‐dependent, specific accumulation of radioactivity in striatum, with a striatum/cerebellum (nonspecific) ratio of 4 at 180 min. Peripheral metabolism accounted for