Deep-Learning for Tidemark Segmentation in Human Osteochondral Tissues Imaged with Micro-computed Tomography
Pith reviewed 2026-05-24 23:16 UTC · model grok-4.3
The pith
U-Net trained on binary cross-entropy and soft Jaccard loss segments the tidemark automatically in PTA-stained micro-CT osteochondral images.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
A U-Net model trained using a combination of binary cross-entropy and soft Jaccard loss performs fully automatic segmentation of the tidemark in PTA-stained osteochondral tissues imaged with micro-computed tomography, achieving intersection over union values of 0.59, 0.70, 0.79, 0.83, and 0.86 within 15 μm, 30 μm, 45 μm, 60 μm, and 75 μm padded zones around the tidemark on cross-validation.
What carries the argument
U-Net neural network trained with binary cross-entropy combined with soft Jaccard loss for binary segmentation of the calcified cartilage interface.
Load-bearing premise
The 35 PTA-stained human samples used for training and cross-validation represent the full range of tidemark appearance, staining variability, and scanner settings encountered in osteoarthritis studies.
What would settle it
A test set of new PTA-stained samples acquired under different staining conditions or scanner settings that produces intersection-over-union scores markedly below the reported cross-validation numbers at each tolerance zone.
Figures
read the original abstract
Three-dimensional (3D) semi-quantitative grading of pathological features in articular cartilage (AC) offers significant improvements in basic research of osteoarthritis (OA). We have earlier developed the 3D protocol for imaging of AC and its structures which includes staining of the sample with a contrast agent (phosphotungstic acid, PTA) and a consequent scanning with micro-computed tomography. Such a protocol was designed to provide X-ray attenuation contrast to visualize AC structure. However, at the same time, this protocol has one major disadvantage: the loss of contrast at the tidemark (calcified cartilage interface, CCI). An accurate segmentation of CCI can be very important for understanding the etiology of OA and ex-vivo evaluation of tidemark condition at early OA stages. In this paper, we present the first application of Deep Learning to PTA-stained osteochondral samples that allows to perform tidemark segmentation in a fully-automatic manner. Our method is based on U-Net trained using a combination of binary cross-entropy and soft Jaccard loss. On cross-validation, this approach yielded intersection over the union of 0.59, 0.70, 0.79, 0.83 and 0.86 within 15 {\mu}m, 30 {\mu}m, 45 {\mu}m, 60 {\mu}m and 75 {\mu}m padded zones around the tidemark, respectively. Our codes and the dataset that consisted of 35 PTA-stained human AC samples are made publicly available together with the segmentation masks to facilitate the development of biomedical image segmentation methods.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript presents the first application of deep learning for automatic tidemark (calcified cartilage interface) segmentation in PTA-stained human osteochondral samples imaged via micro-CT. It employs a U-Net trained with binary cross-entropy combined with soft Jaccard loss and reports 5-fold cross-validation IoU scores of 0.59, 0.70, 0.79, 0.83, and 0.86 at tolerance distances of 15, 30, 45, 60, and 75 μm on a released dataset of 35 samples, with code and data made public.
Significance. If the performance holds under broader conditions, the approach could accelerate 3D semi-quantitative grading of osteoarthritis features by replacing manual tidemark delineation. The public release of the 35-sample dataset, segmentation masks, and code is a clear strength that supports reproducibility and community development of biomedical segmentation methods.
major comments (1)
- [Abstract, results paragraph on cross-validation performance] Abstract and results paragraph on cross-validation performance: the IoU values are obtained from a single cohort of 35 PTA-stained samples imaged under one staining/scanning protocol, with no reported stratification by patient, OA grade, or scanner parameters. This leaves the assumption that the cohort captures the full range of tidemark appearance, staining variability, and technical conditions untested, which is load-bearing for the claim that the method enables fully-automatic segmentation for OA studies in general.
minor comments (3)
- [Methods] Methods section: full training details (hyperparameters, exact U-Net depth, data augmentation strategy, and fold definitions) are referenced only at a high level; explicit listing would strengthen reproducibility claims.
- [Results] Results: no comparison to inter-rater variability among human annotators or to simpler baselines (e.g., intensity thresholding) is provided, which would help contextualize the reported IoU values at each tolerance distance.
- Figure captions and text: the definition of the 'padded zones' around the tidemark (how the tolerance distance is applied to the ground-truth mask) could be stated more explicitly to avoid ambiguity in interpreting the multi-distance IoU metrics.
Simulated Author's Rebuttal
We thank the referee for the constructive feedback and the recommendation for minor revision. We address the single major comment below.
read point-by-point responses
-
Referee: [Abstract, results paragraph on cross-validation performance] Abstract and results paragraph on cross-validation performance: the IoU values are obtained from a single cohort of 35 PTA-stained samples imaged under one staining/scanning protocol, with no reported stratification by patient, OA grade, or scanner parameters. This leaves the assumption that the cohort captures the full range of tidemark appearance, staining variability, and technical conditions untested, which is load-bearing for the claim that the method enables fully-automatic segmentation for OA studies in general.
Authors: We agree that the reported IoU values derive from a single cohort of 35 samples acquired under one consistent PTA-staining and micro-CT protocol, with no stratification by patient, OA grade, or scanner parameters described in the manuscript. This restricts the strength of any claim to broad generalizability. In the revised version we will (i) rephrase the abstract and results paragraph to state explicitly that performance is reported for this specific cohort and acquisition protocol, and (ii) insert a dedicated limitations paragraph that acknowledges the untested variability across staining conditions, scanner parameters, and patient populations and calls for multi-cohort validation. The public release of the dataset and code is intended to support exactly such extensions. revision: yes
Circularity Check
No circularity: performance metrics obtained from standard cross-validation on held-out folds
full rationale
The paper applies a standard U-Net architecture trained with binary cross-entropy plus soft Jaccard loss to segment the tidemark in PTA-stained micro-CT volumes. The reported IoU values (0.59–0.86 across distance-padded zones) are computed directly from held-out folds of the 35-sample dataset; no equation, loss term, or parameter is defined in terms of the target metric itself. No self-citation chain is invoked to justify uniqueness or to substitute for an external result, and the method description contains no ansatz, renaming of known patterns, or fitted-input-called-prediction structure. The evaluation is therefore self-contained against the released data splits and does not reduce to its own inputs by construction.
Axiom & Free-Parameter Ledger
axioms (1)
- domain assumption The distribution of tidemark appearance and imaging artifacts in the 35 training samples is representative of the broader population of human osteochondral tissues.
Forward citations
Cited by 1 Pith paper
-
Automatic Grading of Individual Knee Osteoarthritis Features in Plain Radiographs using Deep Convolutional Neural Networks
Multi-task CNN ensemble achieves kappa 0.82 for KL and high kappas for OARSI features on independent test set, with AUC 0.98 for OA detection.
Reference graph
Works this paper leans on
-
[1]
Computers in biology and medicine 95, 24–33 (2018)
Abidin, A.Z., Deng, B., DSouza, A.M., Nagarajan, M.B., Coan, P., Wism¨ uller, A.: Deep transfer learning for characterizing chondrocyte patterns in phase contrast x-ray computed tomography images of the human patellar cartilage. Computers in biology and medicine 95, 24–33 (2018)
work page 2018
-
[2]
In: 2016 23rd International Conference on Pattern Recognition (ICPR)
Antony, J., McGuinness, K., O’Connor, N.E., Moran, K.: Quantifying radiographic knee osteoarthritis severity using deep convolutional neural networks. In: 2016 23rd International Conference on Pattern Recognition (ICPR). pp. 1195–1200. IEEE (2016)
work page 2016
-
[3]
Bradski, G.: The OpenCV Library. Dr. Dobb’s Journal of Software Tools (2000) 6 Tiulpin A. et al
work page 2000
-
[4]
The Lancet 386(9991), 376–387 (2015)
Glyn-Jones, S., Palmer, A., Agricola, R., Price, A., Vincent, T., Weinans, H., Carr, A.: Osteoarthritis. The Lancet 386(9991), 376–387 (2015)
work page 2015
-
[5]
TernausNet: U-Net with VGG11 Encoder Pre-Trained on ImageNet for Image Segmentation
Iglovikov, V., Shvets, A.: Ternausnet: U-net with vgg11 encoder pre-trained on imagenet for image segmentation. arXiv preprint arXiv:1801.05746 (2018)
work page internal anchor Pith review Pith/arXiv arXiv 2018
-
[6]
Frontiers in Physics 5, 38 (2017)
Karhula, S.S., Finnil¨ a, M.A., Freedman, J.D., Kauppinen, S., Valkealahti, M., Lehenkari, P., Pritzker, K.P., Nieminen, H.J., Snyder, B.D., Grinstaff, M.W., et al.: Micro-scale distribution of ca4+ in ex vivo human articular cartilage detected with contrast-enhanced micro-computed tomography imaging. Frontiers in Physics 5, 38 (2017)
work page 2017
-
[7]
PloS one 12(1), e0171075 (2017)
Karhula, S.S., Finnil¨ a, M.A., Lammi, M.J., Yl¨ arinne, J.H., Kauppinen, S., Rieppo, L., Pritzker, K.P., Nieminen, H.J., Saarakkala, S.: Effects of articular cartilage constituents on phosphotungstic acid enhanced micro-computed tomography. PloS one 12(1), e0171075 (2017)
work page 2017
-
[8]
Osteoarthritis and cartilage 27(1), 172–180 (2019)
Kauppinen, S., Karhula, S., Thevenot, J., Ylitalo, T., Rieppo, L., Kestil¨ a, I., Haapea, M., Hadjab, I., Finnil¨ a, M., Quenneville, E., et al.: 3d morphometric analysis of calcified cartilage properties using micro-computed tomography. Osteoarthritis and cartilage 27(1), 172–180 (2019)
work page 2019
-
[9]
Adam: A Method for Stochastic Optimization
Kingma, D.P., Ba, J.: Adam: A method for stochastic optimization. arXiv preprint arXiv:1412.6980 (2014)
work page internal anchor Pith review Pith/arXiv arXiv 2014
-
[10]
Osteoarthritis and cartilage 25(10), 1680–1689 (2017)
Nieminen, H., Gahunia, H., Pritzker, K., Ylitalo, T., Rieppo, L., Karhula, S., Lehenkari, P., Hæggstr¨ om, E., Saarakkala, S.: 3d histopathological grading of osteochondral tissue using contrast-enhanced micro- computed tomography. Osteoarthritis and cartilage 25(10), 1680–1689 (2017)
work page 2017
-
[11]
Osteoarthritis and cartilage 23(9), 1613– 1621 (2015)
Nieminen, H., Ylitalo, T., Karhula, S., Suuronen, J.P., Kauppinen, S., Serimaa, R., Hæggstr¨ om, E., Pritzker, K., Valkealahti, M., Lehenkari, P., et al.: Determining collagen distribution in articular car- tilage using contrast-enhanced micro-computed tomography. Osteoarthritis and cartilage 23(9), 1613– 1621 (2015)
work page 2015
-
[12]
Radiology 288(1), 177–185 (2018)
Norman, B., Pedoia, V., Majumdar, S.: Use of 2d u-net convolutional neural networks for automated cartilage and meniscus segmentation of knee mr imaging data to determine relaxometry and morphom- etry. Radiology 288(1), 177–185 (2018)
work page 2018
-
[13]
Paszke, A., Gross, S., Chintala, S., Chanan, G., Yang, E., DeVito, Z., Lin, Z., Desmaison, A., Antiga, L., Lerer, A.: Automatic differentiation in pytorch (2017)
work page 2017
-
[14]
Journal of microscopy 250(1), 21–31 (2013)
Pauwels, E., Van Loo, D., Cornillie, P., Brabant, L., Van Hoorebeke, L.: An exploratory study of contrast agents for soft tissue visualization by means of high resolution x-ray computed tomography imaging. Journal of microscopy 250(1), 21–31 (2013)
work page 2013
-
[15]
Magnetic Resonance Materials in Physics, Biology and Medicine 29(2), 207–221 (2016)
Pedoia, V., Majumdar, S., Link, T.M.: Segmentation of joint and musculoskeletal tissue in the study of arthritis. Magnetic Resonance Materials in Physics, Biology and Medicine 29(2), 207–221 (2016)
work page 2016
-
[16]
In: International Conference on Medical image computing and computer-assisted intervention
Ronneberger, O., Fischer, P., Brox, T.: U-net: Convolutional networks for biomedical image segmen- tation. In: International Conference on Medical image computing and computer-assisted intervention. pp. 234–241. Springer (2015)
work page 2015
-
[17]
Annual review of biomedical engineering 19, 221–248 (2017)
Shen, D., Wu, G., Suk, H.I.: Deep learning in medical image analysis. Annual review of biomedical engineering 19, 221–248 (2017)
work page 2017
-
[18]
https://github.com/MIPT-Oulu/solt (2019)
Tiulpin, A.: Solt: Streaming over lightweight transformations. https://github.com/MIPT-Oulu/solt (2019)
work page 2019
-
[19]
Tiulpin, A., Klein, S., Bierma-Zeinstra, S., Thevenot, J., Rahtu, E., van Meurs, J., Oei, E.H., Saarakkala, S.: Multimodal machine learning-based knee osteoarthritis progression prediction from plain radiographs and clinical data. arXiv preprint arXiv:1904.06236 (2019)
work page internal anchor Pith review Pith/arXiv arXiv 1904
-
[20]
Scientific reports 8(1), 1727 (2018)
Tiulpin, A., Thevenot, J., Rahtu, E., Lehenkari, P., Saarakkala, S.: Automatic knee osteoarthritis diagnosis from plain radiographs: a deep learning-based approach. Scientific reports 8(1), 1727 (2018)
work page 2018
-
[21]
In: Scandinavian Conference on Image Analysis
Tiulpin, A., Thevenot, J., Rahtu, E., Saarakkala, S.: A novel method for automatic localization of joint area on knee plain radiographs. In: Scandinavian Conference on Image Analysis. pp. 290–301. Springer (2017)
work page 2017
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