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A harmonized segmentation protocol for hippocampal and parahippocampal subregions: Why do we need one and what are the key goals?

ABSTRACT: The advent of high-resolution magnetic resonance imaging (MRI) has enabled in vivo research in a variety of populations and diseases on the structure and function of hippocampal subfields and subdivisions of the parahippocampal gyrus. Because of the many extant and highly discrepant segmentation protocols, comparing results across studies is difficult. To overcome this barrier, the Hippocampal Subfields Group was formed as an international collaboration with the aim of developing a harmonized protocol for manual segmentation of hippocampal and parahippocampal subregions on high-resolution MRI. In this commentary we discuss the goals for this protocol and the associated key challenges involved in its development. These include differences among existing anatomical reference materials, striking the right balance between reliability of measurements and anatomical validity, and the development of a versatile protocol that can be adopted for the study of populations varying in age and health. The commentary outlines these key challenges, as well as the proposed solution of each, with concrete examples from our working plan. Finally, with two examples, we illustrate how the harmonized protocol, once completed, is expected to impact the field by producing measurements that are quantitatively comparable across labs and by facilitating the synthesis of findings across different studies. © 2016 Wiley Periodicals, Inc.

SUBMITTER: Wisse LEM

PROVIDER: S-EPMC5167633 | biostudies-literature | 2017 Jan

REPOSITORIES: biostudies-literature

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A harmonized segmentation protocol for hippocampal and parahippocampal subregions: Why do we need one and what are the key goals?

Wisse Laura E M LEM Daugherty Ana M AM Olsen Rosanna K RK Berron David D Carr Valerie A VA Stark Craig E L CEL Amaral Robert S C RSC Amunts Katrin K Augustinack Jean C JC Bender Andrew R AR Bernstein Jeffrey D JD Boccardi Marina M Bocchetta Martina M Burggren Alison A Chakravarty M Mallar MM Chupin Marie M Ekstrom Arne A de Flores Robin R Insausti Ricardo R Kanel Prabesh P Kedo Olga O Kennedy Kristen M KM Kerchner Geoffrey A GA LaRocque Karen F KF Liu Xiuwen X Maass Anne A Malykhin Nicolai N Mueller Susanne G SG Ofen Noa N Palombo Daniela J DJ Parekh Mansi B MB Pluta John B JB Pruessner Jens C JC Raz Naftali N Rodrigue Karen M KM Schoemaker Dorothee D Shafer Andrea T AT Steve Trevor A TA Suthana Nanthia N Wang Lei L Winterburn Julie L JL Yassa Michael A MA Yushkevich Paul A PA la Joie Renaud R

Hippocampus 20161115 1

The advent of high-resolution magnetic resonance imaging (MRI) has enabled in vivo research in a variety of populations and diseases on the structure and function of hippocampal subfields and subdivisions of the parahippocampal gyrus. Because of the many extant and highly discrepant segmentation protocols, comparing results across studies is difficult. To overcome this barrier, the Hippocampal Subfields Group was formed as an international collaboration with the aim of developing a harmonized pr ...[more]

PMID: 27862600

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Project description:Recent advances in MRI and increasing knowledge on the characterization and anatomical variability of medial temporal lobe (MTL) anatomy have paved the way for more specific subdivisions of the MTL in humans. In addition, recent studies suggest that early changes in many neurodegenerative and neuropsychiatric diseases are better detected in smaller subregions of the MTL rather than with whole structure analyses. Here, we developed a new protocol using 7 Tesla (T) MRI incorporating novel anatomical findings for the manual segmentation of entorhinal cortex (ErC), perirhinal cortex (PrC; divided into area 35 and 36), parahippocampal cortex (PhC), and hippocampus; which includes the subfields subiculum (Sub), CA1, CA2, as well as CA3 and dentate gyrus (DG) which are separated by the endfolial pathway covering most of the long axis of the hippocampus. We provide detailed instructions alongside slice-by-slice segmentations to ease learning for the untrained but also more experienced raters. Twenty-two subjects were scanned (19-32 yrs, mean age = 26 years, 12 females) with a turbo spin echo (TSE) T2-weighted MRI sequence with high-resolution oblique coronal slices oriented orthogonal to the long axis of the hippocampus (in-plane resolution 0.44 × 0.44 mm2) and 1.0 mm slice thickness. The scans were manually delineated by two experienced raters, to assess intra- and inter-rater reliability. The Dice Similarity Index (DSI) was above 0.78 for all regions and the Intraclass Correlation Coefficients (ICC) were between 0.76 to 0.99 both for intra- and inter-rater reliability. In conclusion, this study presents a fine-grained and comprehensive segmentation protocol for MTL structures at 7 T MRI that closely follows recent knowledge from anatomical studies. More specific subdivisions (e.g. area 35 and 36 in PrC, and the separation of DG and CA3) may pave the way for more precise delineations thereby enabling the detection of early volumetric changes in dementia and neuropsychiatric diseases.

Dataset Information

A harmonized segmentation protocol for hippocampal and parahippocampal subregions: Why do we need one and what are the key goals?

Publications

A harmonized segmentation protocol for hippocampal and parahippocampal subregions: Why do we need one and what are the key goals?

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