Comparison of ¹⁸F-FDG and PiB PET in cognitive impairment

The purpose of this study was to compare the diagnostic accuracy of glucose metabolism and amyloid deposition as demonstrated by ¹⁸F-FDG and Pittsburg Compound B (PiB) PET to evaluate subjects with cognitive impairment. Methods: Subjects were selected from existing participants in the Mayo Alzheimer's Disease Research Center or Alzheimer's Disease Patient Registry programs. A total of 20 healthy controls and 17 amnestic mild cognitive impairment (aMCI), 6 nonamnestic mild cognitive impairment (naMCI), and 13 Alzheimer disease (AD) subjects were imaged with both PiB and ¹⁸F-FDG PET between March 2006 and August 2007. Global measures for PiB and ¹⁸F-FDG PET uptake, normalized to cerebellum for PiB and pons for ¹⁸F-FDG, were compared. Partial-volume correction, standardized uptake value (SUV), and cortical ratio methods of image analysis were also evaluated in an attempt to optimize the analysis for each test. Results: Significant discrimination (P < 0.05) between controls and AD, naMCI and aMCI, naMCI and AD, and aMCI and AD by PiB PET measurements was observed. The paired groupwise comparisons of the global measures demonstrated that PiB PET versus ¹⁸F-FDG PET showed similar significant group separation, with only PiB showing significant separation of naMCI and aMCI subjects. Conclusion: PiB PET and ¹⁸F-FDG PET have similar diagnostic accuracy in early cognitive impairment. However, significantly better group discrimination in naMCI and aMCI subjects by PiB, compared with ¹⁸F-FDG, was seen and may suggest early amyloid deposition before cerebral metabolic disruption in this group.