Positron Emission Tomography images of the brain, obtained with [¹¹C]PE2I, superimposed on coregistered Magnetic Resonance Images. Images show high binding of [¹¹C]PE2I to the dopamine transporter in the striatal regions of the brain. For reference, regions of interest that were automatically generated using a probabilistic anatomical atlas are shown. Each voxel within an atlas-defined region is associated with a probability of belonging to that region. The dotted region boundaries were generated by including all region voxels with probabilities greater than 10%, whereas the solid region boundaries were generated by setting the probability threshold to 50%. The caudate, putamen,midbrain and thalamus are shown (green, blue, magenta and black outlines, respectively). See the article by DeLorenzo et al on pages 1332–1345.