A new method for the in vivo volumetric measurement of the human hippocampus with high neuroanatomical accuracy

Accurate and reproducible in vivo measurement of hippocampal volumes using magnetic resonance (MR) imaging is complicated by the morphological complex ity of the structure. Additionally, separation of certain parts of the hipp ocampus from the adjacent brain structures on MR images is sometimes very d ifficult. These difficulties have led most investigators to either use arbi trary landmarks or to exclude certain parts Of the structure from their mea surements. Eased on three-dimensional MR data, we have developed a reliable in vivo volumetric measurement of the human hippocampus. In contrast to mo st of the previously described volumetric MR-based methods,; we aimed to sa mple the entire hippocampal formation using its true anatomical definition. This was accomplished by relying on the capacity of the BRAINS software to simultaneously visualize in multiple planes, to "telegraph" tracings or cu rsor position from one plane to another, and to simultaneously rely on mult ispectral data from three different image sets (T1, T2, and tissue classifi ed). The methods for identifying boundaries. and measuring the hippocampal volume are described. The method has excellent reliability, sensitivity, an d specificity. The method may be,of use in studies of structure-function re lationships in neuropsychiatric disorders such as schizophrenia, temporal l obe epilepsy, and Alzheimer's disease. Future work will use these measureme nts as training data for a neural net-based technique to identify the anato mical boundaries automatically. Hippocampus 2000;10:752-758. (C) 2000 Wiley -Liss, Inc.