Abstract
In magnetic resonance imaging of the brain, an imaging-preprocessing step removes the skull and other non-brain tissue from the images. But methods for such a skull-stripping process often struggle with large data heterogeneity across medical sites and with dynamic changes in tissue contrast across lifespans. Here we report a skull-stripping model for magnetic resonance images that generalizes across lifespans by leveraging personalized priors from brain atlases. The model consists of a brain extraction module that provides an initial estimation of the brain tissue on an image, and a registration module that derives a personalized prior from an age-specific atlas. The model is substantially more accurate than state-of-the-art skull-stripping methods, as we show with a large and diverse dataset of 21,334 lifespans acquired from 18 sites with various imaging protocols and scanners, and it generates naturally consistent and seamless lifespan changes in brain volume, faithfully charting the underlying biological processes of brain development and ageing.
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Data availability
The large-scale images (N = 21,334) used in this study come from the following publicly available datasets: dHCP (https://biomedia.github.io/dHCP-release-notes/), MAP (https://circlelab.unc.edu/studies/completed-data-collection/multi-visit-advanced-pediatric-brain-imaging-map/), BCP (https://nda.nih.gov/edit_collection.html?id=2848), NDAR (https://nda.nih.gov/edit_collection.html?id=19), HBN (http://fcon_1000.projects.nitrc.org/indi/cmi_healthy_brain_network/), ABIDE (https://fcon_1000.projects.nitrc.org/indi/abide/), IXI (https://brain-development.org/ixi-dataset/), CCNP (https://ccnp.scidb.cn/en/detail?dataSetId=826407529641672704&version=V3&code=o00133), ICBM (https://ida.loni.usc.edu/login.jsp), HCP (https://www.humanconnectome.org/study/hcp-young-adult), SLIM (http://fcon_1000.projects.nitrc.org/indi/retro/southwestuni_qiu_index.html), SALD (http://fcon_1000.projects.nitrc.org/indi/retro/sald.html), DLBS (https://fcon_1000.projects.nitrc.org/indi/retro/dlbs.html), Chinese Adult Brain (https://www.nitrc.org/projects/adultatlas), ABVIB (https://ida.loni.usc.edu/login.jsp), AIBL (https://ida.loni.usc.edu/login.jsp), OASIS3 (https://www.oasis-brains.org) and ADNI (https://ida.loni.usc.edu). Additional images are available at the following links: https://brainlife.io/pub/60ddea776f0f540a79ca53d8 (EMEDEA-PED), https://surfer.nmr.mgh.harvard.edu/docs/synthstrip/ (SynthStrip dataset) and https://fcon_1000.projects.nitrc.org/indi/indiPRIME.html (An Open Resource for Non-human Primate Imaging). Source data are provided with this paper.
Code availability
The source code, training data and trained model are available on GitHub at https://github.com/DBC-Lab/Atlases-empowered_Lifespan_Skull_Stripping. The model is also available for use in iBEAT V2.0 Cloud/Docker (http://www.ibeat.cloud). The source codes of competing methods are also available; BET, https://ftp.nmr.mgh.harvard.edu/pub/dist/freesurfer/tutorial_packages/centos6/fsl_507/doc/wiki/BET(2f)UserGuide.html; 3DSS, https://afni.nimh.nih.gov/pub/dist/doc/program_help/3dSkullStrip.html; ROBEX, https://www.nitrc.org/projects/robex; FreeSurfer, https://surfer.nmr.mgh.harvard.edu/fswiki, version 7.2.0; SynthStrip, https://surfer.nmr.mgh.harvard.edu/docs/synthstrip/#tool; HD-BET, https://github.com/MIC-DKFZ/HD-BET. To assess the significance of the results quantitatively, we conducted statistical analyses P value using one-way ANOVA with repeated measures followed by Dunnett’s multiple comparisons tests. P values were denoted by asterisks: * for P < 0.05, ** for P < 0.01 and *** for P < 0.001. Besides, we used Cohen’s d score as a pivotal metric to convey and quantify the magnitude of the observed effect within the results, using Effect Size Calculators (https://lbecker.uccs.edu).
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Acknowledgements
Limei Wang, Y.S. and Li Wang were supported by the National Institute of Mental Health under award numbers MH133845, MH117943, MH123202 and MH116225. G.L. was supported by the National Institutes of Health under award numbers MH133845, MH117943, MH123202, MH116225, AG075582 and NS128534. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. This work also utilizes approaches developed by NIH grants (U01MH110274 and R01MH104324) and the efforts of the UNC/UMN Baby Connectome Project Consortium.
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Limei Wang: methodology, implementation, validation, writing and editing; Y.S.: validation, review and editing; J.S., R.A.I.B., A.A.-B. and L.D.: editing and providing brain volumes by FreeSurfer/Infant FreeSurfer and so on; G.L.: review; J.T.E.: resources; W.L.: resources; Li Wang: methodology, validation, supervision, review, editing, resources, project administration and funding acquisition.
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Nature Biomedical Engineering thanks Guray Erus, Philipp Vollmuth, Xi-Nian Zuo and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Peer reviewer reports are available.
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Extended data
Extended Data Fig. 1 Comparison of lifespan brain volume by the LifespanStrip method and by previous work.
Lifespan charts in terms of total brain volume (mm3) by previous work50 (left) and by the LifespanStrip framework (right).
Extended Data Fig. 2 Flowchart of the atlases-powered lifespan skull-stripping (LifespanStrip) framework.
a, The LifespanStrip framework consists of a brain-extraction module and a registration module. The brain-extraction module is designed to generate an initial estimation of brain intracranial cavity. The registration module aligns an atlas with the estimated brain to offer personalized prior knowledge. Subsequently, the deformation field is applied to the atlas, resulting in the final brain mask. b, The brain-extraction network integrates dual convolution (DC) and dual transformer (DT), detailed in the bottom right corner. c, The registration module includes both rigid registration and deformable registration components.
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Wang, L., Sun, Y., Seidlitz, J. et al. A lifespan-generalizable skull-stripping model for magnetic resonance images that leverages prior knowledge from brain atlases. Nat. Biomed. Eng 9, 700–715 (2025). https://doi.org/10.1038/s41551-024-01337-w
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DOI: https://doi.org/10.1038/s41551-024-01337-w