How random is the random forest? Random forest algorithm on the service of structural imaging biomarkers for Alzheimer's disease: from Alzheimer's disease neuroimaging initiative (ADNI) database

Abstract

Neuroinformatics is a fascinating research field that applies computational models and analytical tools to high dimensional experimental neuroscience data for a better understanding of how the brain functions or dysfunctions in brain diseases. Neuroinformaticians work in the intersection of neuroscience and informatics supporting the integration of various sub-disciplines (behavioural neuroscience, genetics, cognitive psychology, etc.) working on brain research. Neuroinformaticians are the pathway of information exchange between informaticians and clinicians for a better understanding of the outcome of computational models and the clinical interpretation of the analysis. Machine learning is one of the most significant computational developments in the last decade giving tools to neuroinformaticians and finally to radiologists and clinicians for an automatic and early diagnosis-prognosis of a brain disease. Random forest (RF) algorithm has been successfully applied to high-dimensional neuroimaging data for feature reduction and also has been applied to classify the clinical label of a subject using single or multi-modal neuroimaging datasets. Our aim was to review the studies where RF was applied to correctly predict the Alzheimer's disease (AD), the conversion from mild cognitive impairment (MCI) and its robustness to overfitting, outliers and handling of non-linear data. Finally, we described our RF-based model that gave us the 1^st position in an international challenge for automated prediction of MCI from MRI data.

Keywords: Alzheimer's disease; biomarker; classification; machine learning; magnetic resonance imaging; mild cognitive impairment; neuroimaging; random forest.

Figure 1

Outline of the proposed computer-aided diagnosis (CAD) system tailored to Alzheimer's disease using magnetic resonance imaging brain images. ROI: Region of interest.

Figure 2

Classification process based on the random forest algorithm A redesign of the original inspired figure found from the following website: https://www.linkedin.com/pulse/random-forest-algorithm-interactive-discussion-niraj-kumar/.

Figure 3

Graphical layout of the ensemble's classification models. RF: Random forest.

Figure 4

Boxplots for 9 features (for each class), selected as important in the ensemble's models. HC: Healthy controls; MCI: mild cognitive impairment; cMCI: late MCI; AD: Alzheimer's disease.