Selecting the most relevant brain regions to discriminate Alzheimer's disease patients from healthy controls using multiple kernel learning: A comparison across functional and structural imaging modalities and atlases

Author(s)

Rondina, Jane Maryam ^{[1, 2]} ; Ferreira, Luiz Kobuti ^{[3, 1]} ; de Souza Duran, Fabio Luis ^[1] ; Kubo, Rodrigo ^[4] ; Ono, Carla Rachel ^[4] ; Leite, Claudia Costa ^{[4, 5]} ; Smid, Jerusa ^[6] ; Nitrini, Ricardo ^[6] ; Buchpiguel, Carlos Alberto ^[4] ; Busatto, Geraldo F. ^{[7, 3, 1]}

Affiliation

^[1] Univ Sao Paulo, Fac Med, Dept Psychiat, Lab Psychiat Neuroimaging LIM 21, Sao Paulo - Brazil

^[2] UCL, Inst Neurol, Sobell Dept Motor Neurosci & Movement Disorders, London - England

^[3] Univ Sao Paulo, NAPNA, Sao Paulo - Brazil

^[4] Univ Sao Paulo, Med Sch, Dept Radiol & Oncol, Sao Paulo - Brazil

^[5] Univ North Carolina Chapel Hill, Dept Radiol, Chapel Hill, NC - USA

^[6] Univ Sao Paulo, Dept Neurol & Cognit Disorders Reference Ctr CERE, Sao Paulo - Brazil

^[7] Univ Sao Paulo, Dept & Inst Psychiat, Sao Paulo - Brazil

• Document type: Journal article
• Source: NEUROIMAGE-CLINICAL; v. 17, p. 628-641, 2018.
• Web of Science Citations: 8

Abstract

Background: Machine learning techniques such as support vector machine (SVM) have been applied recently in order to accurately classify individuals with neuropsychiatric disorders such as Alzheimer's disease (AD) based on neuroimaging data. However, the multivariate nature of the SVM approach often precludes the identification of the brain regions that contribute most to classification accuracy. Multiple kernel learning (MKL) is a sparse machine learning method that allows the identification of the most relevant sources for the classification. By parcelating the brain into regions of interest (ROI) it is possible to use each ROI as a source to MKL (ROI-MKL). Methods: We applied MKL to multimodal neuroimaging data in order to: 1) compare the diagnostic performance of ROI-MKL and whole-brain SVM in discriminating patients with AD from demographically matched healthy controls and 2) identify the most relevant brain regions to the classification. We used two atlases (AAL and Brodmann's) to parcelate the brain into ROIs and applied ROI-MKL to structural (T1) MRI, F-18-FDG-PET and regional cerebral blood flow SPECT (rCBF-SPECT) data acquired from the same subjects (20 patients with early AD and 18 controls). In ROI-MKL, each ROI received a weight (ROI-weight) that indicated the region's relevance to the classification. For each ROI, we also calculated whether there was a predominance of voxels indicating decreased or increased regional activity (for F-18-FDG-PET and rCBF-SPECT) or volume (for T1-MRI) in AD patients. Results: Compared to whole-brain SVM, the ROI-MKL approach resulted in better accuracies (with either atlas) for classification using F-18-FDG-PET (92.5% accuracy for ROI-MKL versus 84% for whole-brain), but not when using rCBF-SPECT or T1-MRI. Although several cortical and subcortical regions contributed to discrimination, high ROI-weights and predominance of hypometabolism and atrophy were identified specially in medial parietal and temporo-limbic cortical regions. Also, the weight of discrimination due to a pattern of increased voxel-weight values in AD individuals was surprisingly high (ranging from approximately 20% to 40% depending on the imaging modality), located mainly in primary sensorimotor and visual cortices and subcortical nuclei. Conclusion: The MKL-ROI approach highlights the high discriminative weight of a subset of brain regions of known relevance to AD, the selection of which contributes to increased classification accuracy when applied to F-18-FDG-PET data. Moreover, the MKL-ROI approach demonstrates that brain regions typically spared in mild stages of AD also contribute substantially in the individual discrimination of AD patients from controls. (AU)

• FAPESP's process: 09/17398-1 - Correlation analysis of changes in structural volume, perfusion and glucose metabolism in Alzheimer's disease, mild cognitive impairment and normal aging
• Grantee: Carlos Alberto Buchpiguel
• Support type: Regular Research Grants