Validation of a New Imaging Technique Using the Glucose Metabolism to Amyloid Deposition Ratio in the Diagnosis of Alzheimer's Disease.

OBJECTIVE

Alzheimer' disease (AD) is characterized by increase of cortical amyloid deposition in prodromal stage and subsequent decrease of cerebral glucose metabolism as disease progresses. The present study introduces the voxel-wise metabolism to amyloid deposits ratio (MAR) image and to evaluate its reliability for the diagnosis of AD.

METHODS

Consecutive one-hundred and forty-three subjects with AD and 181 normal subjects who underwent both 18F-FDG PET and 18F-florbetapir (AV-45) PET at baseline were included to this study from the database of Alzheimer's disease neuroimaging initiative (ADNI). After normalizing to a standard stereotactic space, the MAR image was created by dividing each FDG-PET image by corresponding AV-45 PET image using with voxel-wise inter-image computation. We examined voxel wise comparison in the MAR images between AD subjects and normal subjects and compared the diagnostic performances between the MAR image and FDG-PET and AV-45 image.

RESULTS

In the voxel wise comparison, the MAR images of AD subjects exhibited severe and extensive decrease compared with normal subjects in the affected region in both FDG-PET and AV-45, especially in the precuneus /posterior cingulate. The highest t-value was equivalent to FDG-PET and the voxel extent was much greater than the other images. In the ROI analysis, the diagnostic accuracies were 82.6% (sensitivity: 86.7%, specificity: 79.5%), 80.7% (sensitivity: 77%, specificity: 83.4%), and 78.8% (sensitivity: 75.2%, specificity: 81.5%) for the MAR image, FDG-PET, and AV-45, respectively. AUC for the MAR image was 0.904 (95%CI: 0.867-0.942), and was larger than those for FDG-PET (AUC: 0.884, 95%CI: 0.843-0.926), and AV-45 (AUC: 0.847, 95%CI: 0.798-0.897).

CONCLUSION

MAR image reflected not only amyloid deposition but the cerebral glucose metabolisms and successfully classified the subjects with AD. These data suggest that the MAR image might be a more proper appropriate diagnostic marker for AD reflecting cerebral metabolisms and amyloid deposition.