Alzheimer disease and mild cognitive impairment: Integrated pulsed arterial spin-labeling MRI and¹⁸F-FDG PET

Purpose: To compare PET/MR hypoperfusion and hypometabolism in patients with Alzheimer disease (AD) and mild cognitive impairment (MCI) compared with healthy control (HC) participants. Materials and Methods: Maps of cerebral blood flow (CBF; pulsed arterial spin-labeling [ASL] MRI), glucose metabolism (fluorine 18 [¹⁸F] fluorodeoxyglucose [FDG] PET), and gray matter (GM) volume (structural T1-weighted MRI) were calculated from integrated PET/MR data in 45 patients with AD (mean age, 69 years ± 9 [standard deviation]; age range, 51-89 years), 20 patients with MCI (mean age, 64 years ±10; age range, 45-82 years), and 11 HC participants (mean age, 65 years ± 8; age range, 54-80 years) between 2011 and 2014. After preprocessing, voxel-wise analyses of variance, volume of interest, and independent component analyses were performed for comparisons of CBF and glucose metabolism. Results: Analyses revealed high overlap between components, regional and quantitative hypoperfusion, and hypometabolism in patients with AD compared with HC participants in precuneus, parietal, temporal, and occipital cortex. In patients with MCI compared with HC participants, FDG PET exclusively demonstrated quantitative hypometabolism and a component in the precuneus. Volume-of-interest analysis in global GM in patients with AD compared with HC participants showed lower CBF (42 mL/100 g per minute ± 8 vs 49 mL/100 g per minute ± 7, respectively; P = .035) and lower FDG uptake (0.8 ± 0.1 vs 1 ±0.1, respectively; P < .001). Conclusion: In patients with AD, pulsed ASL MRI revealed regional and quantitative abnormalities and components similar to ¹⁸F-FDG PET with a reduced extent. In patients with MCI, ¹⁸F-FDG PET exclusively demonstrated quantitative hypometabolism and a component in the precuneus, indicating higher sensitivity to detect preclinical AD compared with the currently used pulsed ASL MRI sequence.