Evaluation of fluorinated m-tyrosine analogs as PET imaging agents of dopamine nerve terminals: comparison with 6-fluoroDOPA.
Fluorinated m-tyrosine analogs were evaluated as PET imaging agents and compared with 6-fluoroDOPA in the visualization of dopamine nerve terminals.


METHODS
The three m-tyrosine analogs, 6-[18F]fluoro-L-m-tyrosine (6-FMT), 2-[18F]fluoro-L-m-tyrosine (2-FMT) and 6-[18F]fluoro-fluoromethylene-DL-m-tyrosine (6-F-FMMT), were prepared via electrophilic radiofluorination using [18F]acetylhypofluorite. These three analogs, as well as 6-[18F]fluoro-L-DOPA (6-FD), were injected into sets of rhesus monkeys, and serial PET images were acquired. Plasma samples were collected at different times after tracer administration, and metabolite analyses were done using high-performance liquid chromatography (HPLC).


RESULTS
Visual inspection of the PET images obtained using these four tracers showed that the best image contrast was obtained with 6-FMT. Patlak analysis with a reference tissue input function yielded a mean uptake rate constant for 6-FMT of 0.019 min-1, a value twice those for the other tracers including 6-FD.


CONCLUSIONS
These results demonstrate the superiority of 6-[18F]FMT in visualizing dopamine terminals in the rhesus monkey brain and suggest that 6-[18F]FMT is the tracer of choice in the assessment of dopamine metabolism in the living human brain.
DeJesus
O T
OT
Department of Medical Physics, University of Wisconsin Medical School, Madison 53706, USA.
Endres
C J
CJ
Shelton
S E
SE
Nickles
R J
RJ
Holden
J E
JE
D000818:Animals; D001921:Brain / Q000000981:diagnostic imaging / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D004295:Dihydroxyphenylalanine / Q000031:analogs & derivatives*; D004298:Dopamine / Q000378:metabolism*; D005260:Female; D005462:Fluorine Radioisotopes; D008253:Macaca mulatta; D008297:Male; D009411:Nerve Endings / Q000378:metabolism*; D014055:Tomography, Emission-Computed; D014443:Tyrosine / Q000031:analogs & derivatives
D005462:Fluorine Radioisotopes; C043437:fluorodopa F 18; D014443:Tyrosine; D004295:Dihydroxyphenylalanine; D004298:Dopamine