Parcellation of Brain Magnetic Resonance Images using Improved Atlases Selection Model

Introduction: Multiple atlas-based parcellation model has been demonstrated to perform better than single atlas-based parcellation model in terms of accuracy of the parcellation of human brain Magnetic Resonance Images (MRI). The weakness of the existing multiple atlas-based parcellation models is that the level of accuracy is limited if used for the ageing brain due to the presence of age-related changes such as atrophy. Aim: The aim of this study is to develop a novel multiple atlases selection model that ensures improved accuracy for the parcellation of the ageing brain by combining Cost function with the Similarity metric and Atrophy measure for atlases selection. This model is called COSA. Materials and Methods: A dataset with ten brain MRIs and ten atlases was used. A brain MRI was used one at a time as the target image while the remaining images constituted the source images. Using each target image, consensus atlases were obtained for COSA from the combination of a cost function, similarity index, and atrophy measure. These atlases were consequently used to parcellate the target image. Performance was assessed using Dice Coefficient and COSA was compared with existing atlases selection models. The existing atlases selection models investigated were Normalized Mutual Information (NMI), Mutual Information (MI), Correlation Ratio (CR), Normalized Correlation Ratio (NCR), and Least Square Error (LSE). Results: Mean of Dice Coefficient were: COSA = 0.7495196, NMI = 0.7479508, MI = 0.7473333, Jaccard Index = 0.7392522, CR = 0.7358384, NC = 0.7358043, Atrophy Measure = 0.7300867, LSE = 0.7299367, Single Atlas =0.6830223. Conclusion: Results show that COSA performs better than the existing multiple Atlas-based models.