A dual-tracer study of extrastriatal 6-[ super(18)F]fluoro-m-tyrosin e and 6-[ super(18)F]-fluoro-l-dopa Uptake in Parkinson's disease

• Published in: Synapse (New York, N.Y.) N.Y.), 2014-08, Vol.68 (8), p.325-331
• Main Authors: Li, Clarence T, Palotti, Matthew, Holden, James E, Oh, Jen, Okonkwo, Ozioma, Christian, Bradley T, Bendlin, Barbara B, Buyan-Dent, Laura, Harding, Sandra J, Stone, Charles K, DeJesus, Onofre T, Nickles, Robert J, Gallagher, Catherine L
• Format: Article
• Language: English
• ISSN: 0887-4476; 1098-2396
• DOI: 10.1002/syn.21745

6-[ super(18)F]-Fluoro-l-dopa (FDOPA) has been widely used as a biomarker for catecholamine synthesis, storage, and metabolism-its intense uptake in the striatum, and fainter uptake in other brain regions, is correlated with the symptoms and pathophysiology of Parkinson's disease (PD). 6-[ super(18)F]fluoro-m-tyrosin e (FMT), which also targets l-amino acid decarboxylase, has potential advantages over FDOPA as a radiotracer because it does not form catechol-O-methyltransferase (COMT) metabolites. The purpose of the present study was to compare the regional distribution of these radiotracers in the brains of PD patients. Fifteen Parkinson's patients were studied with FMT and FDOPA positron emission tomography (PET) as well as high-resolution structural magnetic resonance imaging (MRI). MRI's were automatically parcellated into neuroanatomical regions of interest (ROIs) in Freesurfer ( http://surfer.nmr.mgh.harvard.edu ); region-specific uptake rate constants (K sub(occ)) were generated from coregistered PET using a Patlak graphical approach. The essential findings were as follows: (1) regional K sub(occ) were highly correlated between the radiotracers and in agreement with a previous FDOPA studies that used different ROI selection techniques; (2) FMT K sub(occ) were higher in extrastriatal regions of relatively large uptake such as amygdala, pallidum, brainstem, hippocampus, entorhinal cortex, and thalamus, whereas cortical K sub(occ) were similar between radiotracers; (3) while subcortical uptake of both radiotracers was related to disease duration and severity, cortical uptake was not. These results suggest that FMT may have advantages for examining pathologic changes within allocortical loop structures, which may contribute to cognitive and emotional symptoms of PD. Synapse 68:325-331, 2014. copyright 2014 Wiley Periodicals, Inc. A comparison of two radiotracers for dopamine metabolism in the brains of Parkinson's patients shows similar regional distributions and relationships to disease severity, but suggests that 6-[ super(18)F]fluoro-m-tyrosine may have advantages for studying extrastriatal structures of relatively high specific uptake such as amygdala.