Classification of neurodegenerative dementia by Gaussian mixture models applied to SPECT images

Gaussian mixture (GM) models can be applied for statistical classification of various types of dementia. As opposed to linear boundaries, they do not only provide the class membership of a case, but also a measure of its probability. This enables an improved interpretation and classification of neurodegenerative dementia datasets which comprise various stages of the disease, and also mixed forms of dementia. In this work, GM models are applied to a total number of 103 technetium-99methylcysteinatedimer (^99mTc-ECD) SPECT datasets of asymptomatic controls (CTR), as well as Alzheimer´s disease (AD) and frontotemporal dementia (FTD) patients in early or moderate stages of the disease. Prior to classification, multivariate analysis is applied: Principal component analysis (PCA) is used for dimensionality reduction, followed by a differentiation of the datasets via multiple discriminant analysis (MDA). A GM model on the resulting discrimination plane is constructed by computing the GM distribution associated with the underlying training set. The posterior probabilities of each case indicate its class membership probability. The performance of GM models for classification is assessed by bootstrap resampling and cross validation. Accuracy and robustness of the method are evaluated for different numbers of principal components (PCs), and furthermore the detection rate of dementia in early stages is calculated. The GM model outperfomes classification with linear boundaries in both predicted accuracy and detection rate of early dementia, and is equally robust.