Atrophy specific MRI brain template for Alzheimer's disease and Mild Cognitive Impairment
Résumé
Rapid brain loss is characteristic for the patients with mild cognitive impairment (MCI) and Alzheimer disease (AD) [1]. In particular, increase of the lateral ventricular volume is strongly correlated with the progression of the disease. Other parts of the brain (hippocampus, entorhinal cortex, etc.) are also subject to the rapid neuronal loss. Many automated image processing methods rely on usage of an anatomical template for registration into a common stereotaxic space for tissue classification, structure segmentation or voxel-based morphometry (VBM). Unfortunately, most commonly available anatomical templates are based on the scans of healthy individuals: for example the MNI-ICBM152 template used in the publicly available SPM and FSL image analysis tools is based on MRI scans of young healthy adults [2], and thus may be suboptimal for image registration techniques. The use of disease-specific templates have been proposed in the literature [3], however high variability in the degree of atrophy for subjects with AD and MCI makes use of a single disease-specific template challenging. Ideally, one would like to use an average MRI template that is matched to the level of atrophy for the subject in question. In this paper we propose a novel approach to generate a continuous four-dimensional template, where the 4th dimension is a surrogate measure of overall brain atrophy, thus making it possible to generate the appropriate representative anatomical template from the wide range of possible levels of atrophy such that it is closely matched to the progression of the disease of the subject, while maintaining continuous one-to-one mapping to the common stereotaxic space.
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