Detection of Alzheimer Pathology In Vivo Using Both (11)C-PIB and (18)F-FDDNP PET

(11)C-Pittsburgh Compound-B ((11)C-PIB) and (18)F-(2-(1-{6-[(2-[(18)F]fluoroethyl)(methyl)amino]-2-naphthyl}ethylidene) ((18)F-FDDNP) have been developed as PET tracers for in vivo imaging of pathology in Alzheimer's disease (AD). The purpose of this study was to directly compare these tracers in patients with AD, patients with mild cognitive impairment (MCI), and healthy controls. Methods: Paired (11)C-PIB and (18)F-FDDNP scans were acquired in 14 patients with AD, 11 patients with amnestic MCI, and 13 controls. For both tracers, parametric images of binding potential (BP(ND)) were generated. Global cortical BP(ND) was assessed using ANOVA. In addition, regional patterns of BP(ND) were compared between diagnostic groups using ANOVA for repeated measures. Results: Global cortical BPND of (11)C-PIB showed higher binding in patients with AD than in controls and patients with MCI. (18)F-FDDNP uptake was higher in patients with AD than in controls, but MCI could not be distinguished from AD or from controls. Global BP(ND) values of both tracers were moderately correlated (r = 0.45; P = 0.005). In MCI, BPND of (11)C-PIB showed a bimodal distribution, whereas values for (18)F-FDDNP were more widespread, with more MCI patients demonstrating increased uptake. Regional (11)C-PIB binding showed different patterns across diagnostic groups, as AD patients showed an overall increase in binding, with the lowest binding in the medial temporal lobe. With (18)F-FDDNP, patterns were similar across diagnostic groups. For all groups, highest values were observed in the medial temporal lobe. Conclusion: Differences in BP(ND) between patients with AD, patients with MCI, and controls were more pronounced for (11)C-PIB. The difference in regional binding, the moderate correlation, and the discrepant findings in MCI suggest that they measure related, but different, characteristics of the disease.