Cited by 405Medical Image Segmentation TechniquesBrain Tumor Detection and ClassificationMedical Imaging and Analysis

Automated segmentation of hippocampal subfields from ultra‐high resolution in vivo MRI

Open access
Van Leemput, Koen, Bakkour, Akram, Benner, Thomas, Wiggins, Graham, Wald, Lawrence L., Augustinack, Jean, Dickerson, Bradford C., Golland, Polina +1 more·2009·Hippocampus

Abstract

Recent developments in MRI data acquisition technology are starting to yield images that show anatomical features of the hippocampal formation at an unprecedented level of detail, providing the basis for hippocampal subfield measurement. However, a fundamental bottleneck in MRI studies of the hippocampus at the subfield level is that they currently depend on manual segmentation, a laborious process that severely limits the amount of data that can be analyzed. In this article, we present a computational method for segmenting the hippocampal subfields in ultra‐high resolution MRI data in a fully automated fashion. Using Bayesian inference, we use a statistical model of image formation around the hippocampal area to obtain automated segmentations. We validate the proposed technique by comparing its segmentations to corresponding manual delineations in ultra‐high resolution MRI scans of 10 individuals, and show that automated volume measurements of the larger subfields correlate well with manual volume estimates. Unlike manual segmentations, our automated technique is fully reproducible, and fast enough to enable routine analysis of the hippocampal subfields in large imaging studies. © 2009 Wiley‐Liss, Inc.

AI snapshot

Written from the paper’s full text.

TL;DR

The paper presents a fully automated Bayesian method for segmenting hippocampal subfields from ultra-high resolution in vivo MRI, using a mesh-based probabilistic atlas learned from manual delineations. In 10 subjects, automated volumes of larger subfields correlated well with manual estimates, while the method was fully reproducible and took about 5 h per subject.

Key findings

  • Automated segmentation took about 5 h per subject on a 2.83 GHz Intel Xeon E5440 processor, whereas manual labeling took approximately 2.5 days per hippocampus.
  • Dice overlap was highest for larger structures: CA2/3 and subiculum (average sizes 935 and 537 mm³) had average Dice around 0.74; CA4/DG (526 mm³) and presubiculum (431 mm³) scored around 0.68 each; CA1 (340 mm³) scored around 0.62; fimbria and hippocampal fissure (81 mm³ each) scored around 0.51 and 0.53.
  • Automated volumes correlated with manual volumes for CA2/3 (r = 0.91, P ≤ 0.0002) and CA4/DG (r = 0.83, P ≤ 0.0028); subiculum correlated at r = 0.60 (P ≤ 0.066), and hippocampal fissure at r = 0.50 (P ≤ 0.14), with systematic underestimation of fissure volume.
  • Average boundary error was below the 380 µm voxel size for most structures, including fimbria; exceptions were CA1 (about 1.17 times voxel size) and hippocampal fissure (almost twice voxel size). Mean intrarater Dice overlap over all structures was 0.79, and automated results were systematically more different from manual segmentations than repeated manual segmentations were from one another.

Methods

  • Design: Bayesian generative model of MRI image formation around the hippocampal area, combining a mesh-based probabilistic atlas prior with a Gaussian likelihood model; parameters optimized via Generalized Expectation-Maximization and MAP estimation, with multi-resolution optimization.
  • Data/sample: Ultra-high resolution T1-weighted MPRAGE scans at 3.0T (380 µm in-plane, TR/TI/TE = 2530/1100/5.39 ms, FOV = 448, FA = 7°, 208 coronal slices, thickness 0.8 mm, acquisition time 7.34 min, five acquisitions) from 10 subjects (six younger, four older cognitively normal; five male, five female; age range 22–89); right hippocampus manually delineated.
  • Analysis: Leave-one-out cross-validation, building an atlas from nine subjects and segmenting the held-out subject; compared automated versus manual segmentations using Dice overlap, average boundary distance, Pearson correlation of volumes, and comparison to repeated manual delineations in two midbody slices from five subjects.

Limitations

  • Stated: Manual segmentations were treated as gold standard but suffer their own errors, including greater consistency in the plane drawn than in cross-sectional directions and possible repeated mistakes by the same operator; a more comprehensive validation would require multiple human operators and repeat scans, which was outside the scope.
  • Stated: The manual delineation protocol was still being validated and refined and was used in its initial form; the caudal “catch-all” hippocampus label varied from 5 to 17% of total hippocampal volume and was excluded from comparisons because its starting point was unavailable to the automated algorithm.
  • Stated/evident: Results are based on T1-weighted images only, with future work needed for T2-weighted or multi-spectral data; the validation sample is small (10 subjects, right hippocampus only) and uses a single-site, single-operator manual reference.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1002/hipo.20615

Cites

26 of 26 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

0 of 4 cited sources checked · 0 supported · 0 flagged

  • Findingown data

    Manual delineation of hippocampal subfields in ultra-high resolution images is extremely time-consuming, taking several days for a full hippocampus in the authors' images.

    “delineating subfields manually in ultrahigh resolution images is an excruciatingly time consuming process (several days for a full hippocampus in our images).”
    • Also stated in: § EXPERIMENTS · plain
      “Using this procedure, each hippocampus takes approximately 2.5 days to label.”
    Quote in the paperSubstantial claim
  • Findingown data

    Automated volume measurements of the larger hippocampal subfields correlate well with manual volume estimates.

    “show that automated volume measurements of the larger subfields correlate well with manual volume estimates.”
    • Also stated in: § DISCUSSION · plain
      “We showed that automated volume measurements of the larger subfields CA2/3, CA4/DG, and, to a lesser degree, subiculum, correlated well with manual volume estimates.”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: Manual delineations provide a valid reference standard ('gold standard') for evaluating the automated segmentation algorithm.
  • Findingown data

    CA2/3 and subiculum had average Dice coefficients of around 0.74 between automated and manual segmentation.

    “CA2/3 and subiculum, the largest structures with an average size of 935 and 537 mm3, respectively, have an average Dice coefficient of around 0.74”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: Manual delineations provide a valid reference standard ('gold standard') for evaluating the automated segmentation algorithm.
  • Findingown data

    CA4/DG and presubiculum had average Dice coefficients of around 0.68 between automated and manual segmentation.

    “whereas CA4/DG (on average 526 mm3) and presubiculum (on average 431 mm3) score around 0.68 each”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: Manual delineations provide a valid reference standard ('gold standard') for evaluating the automated segmentation algorithm.
  • Findingown data

    Automated volumes of CA2/3 are strongly correlated with manual volumes (correlation coefficient 0.91, P ≤ 0.0002).

    “the automatically calculated volumes of CA2/3 and CA4/DG are strongly correlated with the manual ones, with a correlation coefficient of 0.91 (P ≤ 0.0002) and 0.83 (P ≤ 0.0028), respectively.”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: Manual delineations provide a valid reference standard ('gold standard') for evaluating the automated segmentation algorithm.
  • May combine two claims. 8
  • Classified as probably not a substantial claim. 8
  • May combine two claims.

    Findingown data

    Fimbria and hippocampal fissure had average Dice coefficients of around 0.51 and 0.53, respectively, between automated and manual segmentation.

    “Automated segmentation of the fimbria and the hippocampal fissure, the smallest structures with an average volume of only 81 mm3 each, is considerably more challenging, with a Dice coefficient of around 0.51 and 0.53, respectively.”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: Manual delineations provide a valid reference standard ('gold standard') for evaluating the automated segmentation algorithm.
  • May combine two claims.

    Findingown data

    The automated method performs similarly on selected midbody slices as on whole volumes, except for the presubiculum (Dice coefficient 0.55) and the hippocampal fissure (Dice coefficient 0.2).

    “Qualitatively, the automated method performs similarly on these selected slices as on the whole volumes, except for the presubiculum (Dice coefficient decreased to 0.55), and the hippocampal fissure (Dice coefficient only 0.2).”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: Manual delineations provide a valid reference standard ('gold standard') for evaluating the automated segmentation algorithm.
  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Findingown data

    The computational segmentation process for each of the 10 subjects was fully automated and took about 5 h per subject on a 2.83 GHz Intel Xeon E5440 processor.

    “The computational segmentation process for each of the 10 subjects was fully automated and took about 5 h per subject on a 2.83 GHz Intel Xeon E5440 processor.”
    Quote in the paperNot a substantial claim
  • May combine two claims.

    Findingown data

    Automated volumes of subiculum correlate with manual volumes (correlation coefficient 0.60) but the correlation does not reach statistical significance (P ≤ 0.066).

    “Subiculum also correlates to some degree (correlation coefficient 0.60), although the correlation does not reach statistical significance (P ≤ 0.066).”
    Quote in the paperNot a substantial claim
    • The authors state this as an assumption: Manual delineations provide a valid reference standard ('gold standard') for evaluating the automated segmentation algorithm.
  • May combine two claims.

    Findingown data

    With the exception of the hippocampal fissure, the structures most difficult to segment reliably by the human operator are also the most difficult for the automated method; the order in which Dice scores decrease across structures is the same for both methods.

    “With the exception of the hippocampal fissure, the structures that are most difficult to segment reliably by the human operator are also the most difficult for the automated method: the order in which the Dice scores decrease across structures is the same for both methods.”
    Quote in the paperNot a substantial claim
    • The authors state this as an assumption: Manual delineations provide a valid reference standard ('gold standard') for evaluating the automated segmentation algorithm.
  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationnone given

    Generalizing the model and optimization procedures from single-valued to vector-valued intensities is straightforward, allowing the algorithm to directly analyze multi-spectral MRI scans.

    “Furthermore, generalizing the model and the optimization procedures described here from single-valued to vector-valued intensities is straightforward, allowing the algorithm to directly analyze multi-spectral MRI scans as well.”
    Quote in the paperNot a substantial claim
  • Classified as probably not a substantial claim.

    Study design and conductown data

    To place automated performance in the context of human intrarater variability, two consecutive coronal slices in the midbody of the hippocampus in five subjects were re-delineated twice by the same human operator.

    “To place the automated method’s segmentation performance in the context of human intrarater variability, two consecutive coronal slices in the midbody of the hippocampus in a randomly chosen subset of five subjects (three younger and two older subjects; two male and three female; age range 22–89) were re-delineated twice by the same human operator who performed the original segmentations.”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: Manual delineations provide a valid reference standard ('gold standard') for evaluating the automated segmentation algorithm.
  • Classified as probably not a substantial claim.

    Study design and conductown data

    The automated segmentation algorithm was evaluated using a leave-one-out cross-validation strategy: an atlas mesh was built from manual delineations in nine of the 10 subjects and used to segment the remaining subject, repeated for each subject.

    “We evaluated our automated segmentation algorithm using a leave-one-out cross-validation strategy: we built an atlas mesh from the manual delineations in nine of the 10 subjects, and used this to segment the image of the remaining subject. We repeated this process for each of the 10 subjects”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: Manual delineations provide a valid reference standard ('gold standard') for evaluating the automated segmentation algorithm.
  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationreasoning

    The algorithm automatically learns and adapts to each scan's contrast properties, which should make it applicable to images acquired with different pulse sequences, such as T2-weighted protocols.

    “While the results presented here are based on T1-weighted images, the fact that our algorithm automatically learns and adapts to each scan’s contrast properties should make it applicable to images acquired with different pulse sequences as well, for example, the T2-weighted protocols used by some other groups”
    Quote in the paperNot a substantial claim
  • May combine two claims.

    Premisecitation

    The distinct subregions composing the hippocampus have been implicated in different memory subsystems and shown to be differentially affected in normal aging and AD.

    “The distinct subregions composing the hippocampus have been implicated in different memory subsystems (Gabrieli et al., 1997; Zeineh et al., 2003), and shown to be differentially affected in normal aging and AD (West et al., 1994; Fukutani et al., 1995; Small et al., 1999; Small et al., 2000).”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites Gabrieli et al., 1997

      Not checked in the free run.

    • cites Zeineh et al., 2003

      Not checked in the free run.

    • cites West et al., 1994

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Study design and conductnone given

    The manual delineation protocol used for reference segmentations is currently being validated and refined and was used in its initial form.

    “The delineation protocol is currently being validated and refined and is used here in its initial form for the primary purpose of the development and reliability assessment of the automated segmentation technique that is the main focus of the present study.”
    Quote in the paperNot a substantial claim
    • Rests on an assumption: The manual delineation protocol, though still being validated and refined, is adequate for the primary purpose of development and reliability assessment of the automated segmentation technique.
  • May combine two claims.

    Premisecitation

    The probabilistic atlas learning procedure automatically yields sparse atlas representations that avoid overfitting to training data and are better at predicting neuroanatomy in new subjects than conventional probabilistic atlases.

    “As shown in (Van Leemput, (in press)), this procedure automatically yields sparse atlas representations that explicitly avoid overfitting to the training data, and that are therefore better at predicting the neuroanatomy in new subjects than conventional probabilistic atlases.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Van Leemput, (in press)

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Study design and conductreasoning

    Voxels labeled as the 'catch-all' hippocampus label in either the automated or manual segmentation were excluded from comparisons.

    “voxels that were labeled as such in either the automated or manual segmentation were not included in the comparisons.”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: Manual delineations provide a valid reference standard ('gold standard') for evaluating the automated segmentation algorithm.
  • Classified as probably not a substantial claim.

    Study design and conductreasoning

    The study used a multi-resolution optimization strategy to reduce the risk of getting trapped in a local optimum.

    “In order to reduce the risk of getting trapped in a local optimum, we employ a multi-resolution optimization strategy”
    Quote in the paperSubstantial claim
14 of 14
  • The authors state this as an assumption.

    Manual delineations provide a valid reference standard ('gold standard') for evaluating the automated segmentation algorithm.

    “Although manual segmentations were considered the gold standard for evaluating our automated algorithm”
  • The paper relies on this without support.

    The manual delineation protocol, though still being validated and refined, is adequate for the primary purpose of development and reliability assessment of the automated segmentation technique.

    “The delineation protocol is currently being validated and refined and is used here in its initial form for the primary purpose of the development and reliability assessment of the automated segmentation technique that is the main focus of the present study.”
  • The paper relies on this without support.

    Manual delineations suffer from intra- and interobserver variability, which confounds subsequent statistical analyses of the results.

    “Furthermore, manual delineations suffer from intra- and interobserver variability, which confounds subsequent statistical analyses of the results.”
3 of 3

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Intensity-correction method cites the tissue-classification reference

    Minor

    The text attributes its MRI intensity-inhomogeneity correction technique to the 1999b reference, but the reference list identifies the bias-field correction paper as 1999a and the 1999b paper as tissue classification.

1 of 1

Cites

Flagged first, then by citations

Research works printed but not linked: 2

  1. D'Agostino E, 2006, A Unified Framework for Atlas Based Brain Image Segmentation and Registration. Lecture Notes in Computer Science, 136
  2. Press WH, 1992, Numerical Recipes in C. The Art of Scientific Computing

Cited by

Sorted by citations

Authors
Van Leemput, K., Bakkour, A., Benner, T., Wiggins, G., Wald, L. L., Augustinack, J., Dickerson, B. C., Golland, P., & Fischl, B.
Affiliations
  • Harvard University (US)
  • Massachusetts Institute of Technology (US)
Venue
Hippocampus
Publisher
Wiley
Published
2009-04-29
Volume
19
Issue
6
Pages
549-557
ISSN
  • 1050-9631 (ISSN-L)
  • 1098-1063
OpenAlex
W1571837886
Cited by
405
References
26
Citations by year
2026: 7 · 2025: 15 · 2024: 11 · 2023: 14 · 2022: 11 · 2021: 18 · 2020: 32 · 2019: 27 · 2018: 37 · 2017: 40 · 2016: 57 · 2015: 40 · 2014: 39 · 2013: 24 · 2012: 18
FWCI
11.76
Type
journal article
Language
en
Open access
Locations
  • Hippocampus (publishedVersion)
  • PubMed (publishedVersion)
  • PubMed Central (acceptedVersion)
  • DSpace@MIT (Massachusetts Institute of Technology) (submittedVersion, cc-by-nc-sa)
  • PubMed Central
Funders
  • Ellison Medical Foundation
  • National Institutes of Health (BIRN002, RR14075, EB005149)
  • National Institute on Aging (R21AG029840, R01AG029411)
  • National Institute of Neurological Disorders and Stroke (NS052585-01, R01NS051826, P41-RR14075, R01NS052585)
  • National Institute of Biomedical Imaging and Bioengineering (R01EB001550, R01EB006758, U54EB005149)
  • National Center for Research Resources (P41-RR-14075, RR 14075, U24RR021382, R01 RR1659401A1, R01-RR16594, P41RR014075, P41RR013218, BIRN002, R01RR016594, P41 RR13218)
Topics
  • Physical Sciences › Computer Science › Computer Vision and Pattern Recognition › Medical Image Segmentation Techniques
  • Life Sciences › Neuroscience › Neurology › Brain Tumor Detection and Classification
  • Physical Sciences › Engineering › Biomedical Engineering › Medical Imaging and Analysis
Keywords
hippocampal subfields, automatic segmentation, ultra-high resolution MRI, Bayesian inference, hippocampal formation, statistical image models, manual segmentation comparison
MeSH terms
Adult, Aged, Aged, 80 and over, Aging, Algorithms, Alzheimer Disease, Automation, Bayes Theorem, Hippocampus, Humans, Magnetic Resonance Imaging, Middle Aged, Organ Size, Young Adult

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