Superiority of FDG-PET over Amyvid imaging in diagnosis of Mild Cognitive Impairment and Alzheimer's disease

Objectives: This study demonstrates how Aβ-amyloid tracer ¹⁸F-florbetapir (Amyvid) and ¹⁸F-FDG-PET regional brain measurements correlate with clinical status of the subjects with Alzheimer disease (AD), Mild Cognitive Impairment (MCI) and Normal Controls (NC).

Methods: 19 patients with a clinical diagnosis of AD, 23 with MCI and 21 elderly controls underwent PET/CT imaging with Amyvid and FDG. Regional brain measurements were carried out by drawing ROIs manually on PET/CT fused image slices around Frontal (F), Temporal (T), and Prieto-Occipital (PO) lobes, and the cerebellum based on predefined anatomical criteria. Global glucose metabolism and Global amyloid burden were calculated by averaging mean standardized uptake values (GSUVmean). Then, the data were normalized by calculating GSUVmean ratio of each region using cerebellum as a reference. Finally, regional metabolic and amyloid burden ratios were compared to Mini-Mental State Examination (MMSE).

Results: GSUVmean ratios with FDG for F, PO and T regions for all the subjects has a significant correlation with MMSE (P < 0.001) the same is true for F (P < 0.001), PO (P = 0.007) and T (P = 0.001) when only MCI and AD cases together were selected. In AD Group Only F (P = 0.002) and T (P = 0.006) regions and in MCIs only F (P = 0.027) and in NC, T region significantly correlated with MMSE (P = 0.023). With Amyvid Imaging significant negative correlation was found only in PO (P = 0.003) and T (P = 0.021) regions when all cases were selected; and in PO (P = 0.025) and T (P = 0.046) when only MCI and AD group together were selected. in which PO showed a more significant correlation. There was no significant correlation with MMSE in individual groups and also F region had no correlate with MMSE in any group.

Conclusion: Overall FDG-PET indicated a better correlation with clinical status of the demented subjects in all different regions as well as being more accurately related to the severity of dementia than Amyvid in AD diagnosis. Furthermore, Dementia showed to be more related to the Amyloid burden in prieto-occipital followed by temporal than frontal region.