Quantitative comparison of 21 protocols for labeling hippocampal subfields and parahippocampal subregions in in vivo MRI: Towards a harmonized segmentation protocol.

An increasing number of human in vivo magnetic resonance imaging MRI studies have focused on examining the structure and function of the subfields of the hippocampal formation the dentate gyrus CA fields 1 3 and the subiculum and subregions of the parahippocampal gyrus entorhinal perirhinal and parahippocampal cortices The ability to interpret the results of such studies and to relate them to each other would be improved if a common standard existed for labeling hippocampal subfields and parahippocampal subregions Currently research groups label different subsets of structures and use different rules landmarks and cues to define their anatomical extents This paper characterizes both qualitatively and quantitatively the variability in the existing manual segmentation protocols for labeling hippocampal and parahippocampal substructures in MRI with the goal of guiding subsequent work on developing a harmonized substructure segmentation protocol