What is the HSG protocol?
This protocol is the culmination of many years of effort by a large community of researchers aiming to improve validity in segmentation of hippocampal subfields. A full account of the development of this protocol can be read about in our recent published paper available here: http://dx.doi.org/10.1002/hipo.70073
Broadly speaking, the protocol utilize a combination of macrostructural landmarks and geometric heuristics to arrive at a protocol that balance capturing underlying “ground truth” anatomy with feasibility given limited information inherent to MR imaging. The protocol has been developed and tested across a wide range of ages and for cases with age-related atrophy in the hippocampus, and has shown both intra- and inter-rater consistency in boundary placement.
How to use the protocol
There are two broader requirements to ensure valid use of this protocol. One relates to the expertise and knowledge of the people involved in tracing based on the rules specified in the protocol, and the second one relates to the image quality required for reliable and valid tracing of subfields. Below follow a brief summary of these two requirements, including our personal recommendations on how to approach them in a way that promotes reliability and validity.
Anatomical expertise and knowledge
Accurate and reliable tracing of hippocampal subfields requires extensive knowledge of anatomy of the hippocampus, regardless of the protocol used. Familiarity with protocol-specific details such as important landmarks not necessarily located in the hippocampal area is also essential. Each lab is strongly encouraged to establish local procedures for training new tracers and conducting reliability checks on segmentation work, whether performed by novices or experts.
Acquisition type and image quality
High-quality imaging is essential for accurate hippocampal subfield segmentation. This protocol is specifically designed for T2-weighted imaging with high coronal in-plane resolution. Detailed acquisition guidelines can be found on our Acquisition Working Group page (available here) and are discussed in a previous publication (available here).
Images used for hippocampal subfield segmentation must undergo quality checks to address common artifacts that affect the reliability and validity of tracings. A dedicated page on QC tailored to this protocol will be added. However, for a broader perspective, our recent paper on best practices for hippocampal MRI QC is also available here.
Accessing the protocol
All resources of the protocol are made publicly available and are free to use under a Creative Commons license (CC BY-NC). All resources related to the protocol, including the protocol itself as well as data sets for reliability assessment, can be found at this link: https://www.nitrc.org/projects/hsg_protocol.
How to cite the HSG protocol:
Cite in text as (Daugherty et al., 2025; Olsen et al., 2019) if using the HSG Harmonized Protocol for subfield segmentation in hippocampal body.
Include the following language in the manuscript: “The protocol to segment and label hippocampal subfields on MRI was developed by the Hippocampal Subfields Group (HSG), an international working group that was launched in 2015, funded in part by the National Institutes of Health (NIA R01-AG070592). For up-to-date information on the HSG, see https://hippocampalsubfields.com/.”
References:
- Daugherty, A.M., Carr, V., Canada, K.L., Rådman, G., Brown, T., Augustinack, J., Amunts, K., Bakker, A., Berron, D., Burggren, A., Chetelat, G., de Flores, R., Ding, S.-L., Huang, Y., Insausti, R., Johnson, E., Kanel, P., Keresztes, A., Kedo, O., Kennedy, K.M., Lee, J., Malykhin, N., Martinez, A., Mueller, S., Mulligan, E., Ofen, N., Palombo, D., Pasquini, L., Pluta, J., Raz, N., Riggins, T., Rodrigue, K.M., Saifullah, S., Schlichting, M.L., Stark, C., Wang, L., Yushkevich, P., La Joie, R., Wisse, L., Olsen, R., the Alzheimer’s Disease Neuroimaging Initiative, the Hippocampal Subfields Group, 2025. Harmonized Protocol for Subfield Segmentation in the Hippocampal Body on High-Resolution in vivo MRI from the Hippocampal Subfields Group (HSG). Hippocampus, 36(2), e70073. doi:10.1002/hipo.70073.
- Olsen, R.K., Carr, V.A., Daugherty, A.M., La Joie, R., Amaral, R.S.C., Amunts, K., Augustinack, J.C., Bakker, A., Bender, A.R., Berron, D., Boccardi, M., Bocchetta, M., Burggren, A.C., Chakravarty, M.M., Chételat, G., de Flores, R., DeKraker, J., Ding, S.-L., Geerlings, M.I., Huang, Y., Insausti, R., Johnson, E.G., Kanel, P., Kedo, O., Kennedy, K.M., Keresztes, A., Lee, J.K., Lindenberger, U., Mueller, S.G., Mulligan, E.M., Ofen, N., Palombo, D.J., Pasquini, L., Pluta, J., Raz, N., Rodrigue, K.M., Schlichting, M.L., Lee Shing, Y., Stark, C.E.L., Steve, T.A., Suthana, N.A., Wang, L., Werkle-Bergner, M., Yushkevich, P.A., Yu, Q., Wisse, L.E.M., Hippocampal Subfields Group, 2019. Progress Update From the Hippocampal Subfields Group. Alzheimer’s & Dementia: Diagnosis, Assessment & Disease Monitoring, 11, 439–449. doi:10.1016/j.dadm.2019.04.001
- Grant Funding: NIH/NIA R01-AG070592 (multi-site award; lead PI L. Wang)