Assessing Mild Cognitive Impairment Progression using a Spherical Brain Mapping of Magnetic Resonance Imaging

Background: The early diagnosis of Alzheimer's Disease (AD), particularly in its prodromal stage, Mild Cognitive Impairment (MCI) remains still a challenge. Many computational tools have been developed to successfully explore and predict the disease progression. In this context, the Spherical Brain Mapping (SBM) proved its ability in detecting differences between AD and aged subjects without symptoms of dementia. Being a very visual tool, its application in predicting MCI conversion to AD could be of great help to understand neurodegeneration and the disease progression.  
Objective: In this work we aim at: predicting the conversion of MCI affected subjects to AD more than 6 months in advance of their conversion session and understanding the progression of the disease by predicting neuropsychological test outcomes from MRI data. 
Methods: In order to do so, SBM is applied to a series of MRI scans from the Alzheimer's Disease Neuroimaging Initiative (ADNI). The resulting spherical brain maps show statistical and morphological information of the brain in a bidimensional plane, performing at the same time a significant feature reduction, that provides a feature vector used in classification analysis. 
Results: The study achieves up to 92.3% accuracy in the AD vs normal controls (CTL) detection, and up to a 77.6% in detection a of MCI conversions when trained with AD and CTL subjects. The prediction of neuropsychological test outcomes achieved R² rates up to more than 0.5. Significant regions according to t-test and correlation analysis match reported brain areas in the literature. 
Conclusion: The results prove that Spherical Brain Mapping offers good ability to predict conversion patterns and cognitive state, at the same time that provides an additional aid for visualizing a two-dimensional abstraction map of the brain.