Region of Interest-based [18F]Fluorodeoxyglucose PET identification of patients with MCI due to Alzheimer disease and healthy controls. An European Alzheimer Disease Consortium (EADC) study

Anemerging issue in neuroimaging is to assess the diagnostic reliability of PET and its application in clinical practice.
Weaimed at assessing the accuracy of brain FDG-PET in discriminating patients withMCI due to Alzheimer3s
disease and healthy controls. Sixty-two patients with amnestic MCI and 109 healthy subjects recruited in five
centers of the European AD Consortium were enrolled. Group analysis was performed by SPM8 to confirm metabolic
differences. Discriminant analyseswere then carried out using the mean FDG uptake values normalized to
the cerebellumcomputed in 45 anatomical volumes of interest (VOIs) in each hemisphere (90 VOIs) as defined in
the Automated Anatomical Labeling (AAL) Atlas and on 12 meta-VOIs, bilaterally, obtained merging VOIs with
similar anatomo-functional characteristics. Further, asymmetry indexes were calculated for both datasets. Accuracy
of discrimination by a Support VectorMachine (SVM) and the AAL VOIs was tested against a validatedmethod
(PALZ). At the voxel level SMP8 showed a relative hypometabolism in the bilateral precuneus, and posterior
cingulate, temporo-parietal and frontal cortices. Discriminant analysis classified subjects with an accuracy ranging
between .91 and .83 as a function of data organization. The best valueswere obtained froma subset of 6 meta-
VOIs plus 6 asymmetry values reaching an area under the ROC curve of .947, significantly larger than the one obtained
by the PALZ score. High accuracy in discriminatingMCI converters from healthy controls was reached by a
non-linear classifier based on SVM applied on predefined anatomo-functional regions and inter-hemispheric
asymmetries. Data pre-processingwas automated and simplified by an in-house created Matlab-based script encouraging
its routine clinical use. Further validation toward nonconverter MCI patients with adequately long
follow-up is needed.