Dual-assessment of functional and pathological changes in Alzheimer`s disease using single (11)C-PIB PET

Abstract

Objectives: In most studies, the association between functional (regional cerebral glucose metabolism) and pathological information (brain amyloid plaque load) have been separately investigated using two different traceres, 11C-PIB and 18F-FDG PET in assessment of of Alzheimers disease (AD). In this study, we investigated the possibility of functional R1 map (relative flow delivery, K1 region of interest/K1 reference region) from PIB PET as alternative functional map in stead of FDG PET. Methods: Thirty eight subjects (8 AD and 12 MCI patients, 18 normal volunteers) underwent dynamic 11C-PIB PET scans with 90 mins scan duration and 18F-FDG scans with 30 mins after injection. Parametric images of R1 for 11C-PIB PET were generated using multilinear reference tissue models (MRTM2).1 To compare the brain regions with perfusion and metabolic abnormalities on 11C-PIB and FDG PET quantitatively, R1 map and FDG images underwent ztransformation with respect to each normal average and SD. The association of the number of abnormal voxels and mean z-value between R1 map obtained from PIB PET and glucose metabolism obtained from FDG PET was evaluated in the entire brain excluding cerebellum. Results: Z-values of each group were well reflected the severity of AD. At a z threshold of 2.97 for both R1 PIB and FDG, the number of abnormal voxels across the entire brain showed a correlation, and the mean z-values of abnormal voxels between them were highly correlated (r = 0.86, P < 0.0001). Conclusions: The relative perfusion obtained from PIB PET was well correlated with those of metabolic abnormality in the entire brain. This study may suggest that a single PIB PET study with R1 map could provide the sufficient information in the distribution of pathologic and metabolic abnormalities in disease progression.