Extrastriatal mean regional uptake of fluorine-18-FDOPA in the normal agedbrain - An approach using MRI-aided spatial normalization

The aim of this study was to define the mean regional 6-[F-18]fluoro-L-dopa (FDOPA) uptake rate constant (Ki) values in the striatal and extrastriatal regions of the brain of normal subjects using magnetic resonance imaging ( MRI)-aided spatial normalization of the FDOPA K-i image and using automatic region of interest (ROI) analysis. Dynamic three-dimensional FDOPA positro n emission tomography (PET) and three-dimensional magnetic resonance (MR) i mages were acquired in 13 aged normal subjects. The FDOPA add image and the K-i image of each subject were transformed into standard stereotactic spac e with the aid of individual coregistered MR image. The mean regional K-i v alues of the striatal and extrastriatal regions before normalization were c ompared with the respective values after normalization. Then automatic ROI analysis was performed on the MRI-aided spatially normalized K-i images of the 13 normal subjects. The K-i values on original images and those on spat ially normalized images were in good agreement, indicating that the spatial normalization technique did not change the regional K-i values appreciably . Automatic ROI analysis of the spatially normalized FDOPA K-i images of th e normal subjects, showed high K-i values in ventral and dorsal regions of the midbrain, amygdala, hippocampus, and medial prefrontal cortex, in addit ion to caudate nucleus and putamen, which correspond to the dopaminergic pr ojections in the brain. Spatial normalization technique helped to establish a database of FDOPA K-i images of normal subjects and high K-i values were observed widely besides striatal regions corresponding to the dopaminergic projections in the brain. (C) 2000 Academic Press.