Comparison of the diagnostic performance of FDG-PET and VBM-MRI in very mild Alzheimer’s disease

Abstract

The aim of this study was to compare the diagnostic performance of( 18)F-fluorodeoxyglucose (FDG) positron emission tomography (PET) and voxel-based morphometry (VBM) on magnetic resonance imaging (MRI) in the same group of patients with very mild Alzheimer's disease (AD). Thirty patients with very mild AD (age 67.0+/-5.8 years; MMSE score 25.5+/-1.2, range 24-28), 32 patients with mild AD (age 67.0+/-4.5 years, MMSE score 22.1+/-0.8, range 21-23) and 60 age- and sex-matched normal volunteers underwent both FDG-PET and three-dimensional spoiled gradient echo MRI. Statistical parametric mapping was used to conduct voxel by voxel analysis and Z score mapping. First, the region of interest (ROI) maps of significant reductions in glucose metabolism and grey matter density in the mild AD patients were defined. Secondly, analysis of receiver operating characteristic (ROC) curves for Z scores in the ROI maps discriminating very mild AD patients and normal controls was performed. In mild AD patients, FDG-PET indicated significant reductions in glucose metabolism in the bilateral posterior cingulate gyri and the right parietotemporal area, while VBM analysis showed a significant decrease in grey matter volume density in the bilateral amygdala/hippocampus complex, compared with the normal control group. ROC analysis showed that in very mild AD patients the accuracy of FDG-PET diagnosis was 89% and that of VBM-MRI diagnosis was 83%. The accuracy of the combination of FDG-PET and VBM-MRI diagnosis was 94%. In very mild AD, both FDG-PET and VBM-MRI had high accuracy for diagnosis, but FDG-PET showed slightly higher accuracy than VBM-MRI. Combination of the two techniques will yield a higher diagnostic accuracy in very mild AD by making full use of functional and morphological images.