Monoamine neuron innervation of the normal human brain: an 18F-DOPA PET study

18F-DOPA positron emission tomography (PET) has been used for two decades to study the organization and pathology of the striatal dopamine system in the human brain, particularly in Parkinson's disease. High resolution 3D PET allows a more detailed analysis than previously available and was employed in this study to determine the regional uptake of 18F-DOPA in control brain. Eleven healthy volunteers underwent 18F-DOPA PET with a region of interest (ROI) study performed using individual volumetric MRI's coregistered to the PET ADD image. A Patlak linear graphical analysis was undertaken to obtain influx constant (Ki) values. The highest Ki values were from neostriatal areas, with a rostrocaudal gradient of increasing Ki values from head of caudate nucleus to rostral putamen to caudal putamen. However, Ki values for transaxial slices from dorsal to ventral through the caudate and putamen were uniform. Ventral striatum Ki was 81% with red nucleus and globus pallidus Ki values of approximately 40% of neostriatum. In limbic areas, highest values were obtained from amygdala (35% neostriatal Ki). Neocortical Ki values varied from 22% in temporal pole to 6% in occipital cortex of neostriatal values. Hypothalamic Ki was high (45%) in comparison to thalamus (17%) and retina (17%). 18F-DOPA is taken up by serotonin (raphe, 51%), and noradrenaline (locus coeruleus, 37%) as well as dopamine neurons. These data indicate that 18F-DOPA PET can be used with detailed, anatomically based ROIs as a tool for in vivo analysis of regional changes in monoamine neuron systems throughout the brain in Parkinson's disease and other disorders.