REVIEW 3 major objections 5 minor 32 references
VIDS-Seg: Towards Reliable Uncertainty Quantification in Pediatric Cardiac Ultrasound Segmentation
T0 review · 3 major / 5 minor · reviewed 2026-08-12 · deepseek-v4-flash
Pith's one-line read An adult-trained cardiac segmentation model can detect its own silent failures on infant echocardiograms by attaching a lightweight variational head that raises uncertainty wherever the distribution shifts.
desk verdict A promising VIDS-to-segmentation extension whose energy function, as written, requires test labels the algorithm never sees—the empirical study is solid enough to warrant major revision rather than a desk reject. read the letter →
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
The reading
What carries the argument
The central object is an adaptive prior over segmentation-head parameters, learned by variational inference. VIDS-Seg keeps the U-Net encoder-decoder frozen and treats the final 1x1 convolution (weight and bias) as the only stochastic parameters, so the posterior over $\theta$ has just $d_\theta = 2D+2$ dimensions for binary segmentation. An inference network $h_\gamma$ receives a spatial-pooled embedding of the test image concatenated with the mean and standard deviation of pooled embeddings of a context set of training images, and outputs the variational mean and log-variance. The prior is defined through an energy function that averages pixel log-likelihoods over training and test images, and the inference network is trained over bootstrap-subsampled synthetic environments with a cross-environment ELBO plus a variance penalty, which is the mechanism intended to make uncertainty grow under distribution shift. This machinery does the work of producing entropy maps that localize where errors occur.
What would settle it
Evaluate VIDS-Seg on a held-out pediatric cohort from a different center or on a different shift type, such as adult patients with severe cardiomyopathy, and compute the NCC gap against the deep ensemble; if the advantage disappears or inverts when the shift is not mimicked by adult bootstrap subsamples, the synthetic-environment premise fails. A simpler check: measure whether the variational posterior's sigma, which is supposed to widen for novel inputs, actually correlates with the infant-versus-adult distance in the embedding space across individual cases.
Extended reading notes
Core claim
The paper claims that uncertainty quantification under covariate shift can be made tractable for dense image segmentation by applying amortized variational inference only to a lightweight 1x1 prediction head on top of a frozen segmentation network. The resulting method, VIDS-Seg, conditions its posterior on a summary of the adult training context and the test image, so predictive entropy widens when the test image is atypical. Across age strata in a pediatric echocardiography dataset, VIDS-Seg matches the Dice and Hausdorff performance of a 10-member deep ensemble and PHiSeg, while achieving substantially higher normalized cross-correlation between predicted entropy and per-pixel error on both non-infant and infant groups. The claim extends beyond quality metrics: more localized uncertainty yields lower and lower-variance ejection-fraction error for infants and a higher AUROC (0.94) for flagging cardiac malfunction than the baselines.
Load-bearing premise
VIDS-Seg assumes that bootstrap subsamples of the adult training set reproduce the kind of distribution shift that makes infant echocardiograms out-of-distribution, so that a prior trained on those synthetic shifts widens for real infants; this premise is never checked against pediatric data during training.
Editorial extensions
If this is right
- A frozen adult-trained segmentation model can gain an OOD-aware uncertainty signal by adding VIDS-Seg's head, with no retraining of the backbone and no pediatric labels.
- On pediatric echocardiography, VIDS-Seg's uncertainty-error alignment beats both a 10-member deep ensemble and PHiSeg, and the ranking survives post-hoc temperature scaling fitted on adult data.
- Infants are the only age stratum where all tested models drop substantially (DSC around 0.84-0.85), so they are the subgroup most in need of uncertainty-based guarding.
- The better-localized uncertainty carries downstream: VIDS-Seg gives lower and less variable ejection-fraction MAE for infants and the highest AUROC for detecting EF below 50%.
- Post-hoc calibration improves all methods' NCC but does not close the gap, indicating the advantage is spatial localization, not just confidence scaling.
Reading between the lines
- If the mechanism generalizes, the same bootstrap-subsample training could flag other silent-failure subgroups, such as unusual adult anatomies or different ultrasound vendors and acoustic windows, provided the embedding space captures those shifts; the paper only demonstrates the pediatric echocardiography case.
- A testable extension would be to check whether VIDS-Seg's NCC advantage persists under non-anatomical shifts, such as image corruption or label noise, where the synthetic environments may or may not mimic the shift.
- The paper evaluates pixel-level entropy, but clinical use needs a scalar decision rule; aggregating entropy into a per-study alert and testing its operating characteristic against expert review would be the missing step toward deployment.
- Because the inference network conditions on pooled embeddings, the method implicitly assumes that global appearance statistics summarize distributional novelty; shifts that live in fine spatial structure rather than global features could be missed.
Signed reviews
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript proposes VIDS-Seg, an extension of the VIDS framework to dense image segmentation. A frozen U-Net embedding is combined with a stochastic 1x1 prediction head whose parameters are drawn from a variational posterior produced by an inference network conditioned on training-set and test-set embeddings. The method is trained on adult EchoNet-Dynamic data using synthetic environments formed by bootstrap subsampling and evaluated zero-shot on pediatric EchoNet-Pediatric. The paper reports that VIDS-Seg matches baseline segmentation accuracy across age groups, achieves substantially higher pixel-wise NCC between predictive entropy and segmentation error for both non-infant and infant subgroups, that this advantage persists after temperature scaling, and that it translates into lower EF MAE and higher AUROC for cardiac malfunction detection in infants.
Significance. If the method and results are correct, the paper makes a useful contribution: it provides a practical way to make OOD-aware uncertainty quantification tractable for dense segmentation, and it gives empirical evidence that uncertainty quality can be improved without pediatric labels. The comparison against deep ensembles and PHiSeg, the use of a public adult/pediatric dataset pair, the Wilcoxon signed-rank tests, and the temperature-scaling analysis are all strengths. However, the method section contains a load-bearing inconsistency between the energy function and the inference algorithm, together with an ambiguity in the test-side embedding, and these issues must be resolved before the empirical claims can be accepted.
major comments (3)
- [Section 3.2, Eq. (8) vs Algorithm 1] The adaptive prior in Eq. (8) contains the term (1/HW) * sum_{h,w} log p(y*_{hw} | x*, theta), which requires the ground-truth segmentation of the test image. Algorithm 1, however, provides only x* to the inference network h_gamma (steps 1-3) and never receives y*. With this objective, the variational distribution q_phi is trained to approximate p(theta | x1:N, x*, y*), a label-conditioned posterior, while at test time it is evaluated from x* alone. Since y* is not part of the input to h_gamma, the target posterior is not a function of the network's input, and the trained network cannot consistently reproduce it. This directly affects the variance output by h_gamma, which is the signal behind every reported NCC/EF/AUROC result. Please either replace the y* term in Eq. (8) with a label-free marginalization, for example a Monte Carlo average over the predictive distribution as in the original VIDS energy of Eq. (2), and re-run the experiments, or explicitly describe how labels are used during training and justify why the label-conditioned posterior is computable at test time.
- [Section 3.2, spatial aggregation and Algorithm 1] The text states that the inference network input has dimension 4D, formed from the context summary in R^{2D} and the test embedding g_xi(x*). But g_xi(x*) is defined as a dense map in R^{D x H x W}, and Algorithm 1 step 2 does not spatially reduce it. A fully-connected h_gamma cannot take a spatial map as input, and the stated dimensions do not add up (2D + D is 3D, not 4D). Please specify the exact test-side pooling operation and the precise vector passed to h_gamma; this is needed to reproduce Algorithm 1.
- [Section 4.2.1-4.2.2] The infant subgroup is identified as OOD after observing that all models degrade most on that group, and the uncertainty and downstream analyses are then performed only on this selected subset. This is a selection on the outcome: the subgroup used to evaluate OOD detection is chosen using the same test data on which uncertainty quality is measured. To support the claim that VIDS-Seg can flag silent failures for underrepresented subgroups at deployment, the OOD subgroup should either be prespecified, or the selection should be made on a separate development set, or a sensitivity analysis across all age strata should be provided.
minor comments (5)
- [Section 4.2.2] The metric is introduced as the NCC 'between the per-pixel entropy map and a binary error map', but the error map is then defined as the pixel-wise cross entropy between mean logits and the ground-truth mask. Please clarify which error map was actually used for the reported numbers.
- [Section 4.1.2 and Eq. (11)] The ejection fraction is described as computed with Simpson's biplane method, but only a single apical four-chamber view is used. Please clarify whether a single-plane modification was applied, since the standard biplane method requires two orthogonal views.
- [Figure 2] Segmentation accuracy is compared across age groups only descriptively; please add pairwise statistical tests or confidence intervals for DSC and HD95 to support the claim that VIDS-Seg 'matches' the baselines.
- [Section 4.2.2 / Table 1] The text says temperature scaling is applied to 'all three baselines', but Table 1 also includes temperature-scaled VIDS-Seg; please rephrase to make clear that VIDS-Seg is included.
- [Algorithm 1 and Section 4.2.2] Algorithm 1 (step 10) says the entropy map is computed from the per-sample maps {p^(s)}, while the text defines H_p from the mean probability sbar_p; please align the formula with the algorithm.
Circularity Check
Eq. (8) defines the adaptive prior through the test label y*, which Algorithm 1 cannot access, so the claimed OOD-widening uncertainty reduces to label-conditioned training rather than a label-free prediction.
-
self definitional
[Section 3.2, Eq. (8); Section 3.4, Algorithm 1; Section 3.1, Eq. (3)]
"E(θ;x_1:N ,x^*) = \sum_{i=1}^N \frac{1}{HW}\sum_{h,w} \log p(y_{hw}|x_i,\theta) + \frac{1}{HW}\sum_{h,w} \log p(y^*_{hw}|x^*,\theta). (8) ... (µ,logσ) ← hγ(\bar{g}(x_{1:N}), gξ(x^*)) ... By design of the adaptive prior, this should occur more frequently for OOD inputs."
The energy defining the adaptive prior includes the observed test-label map y* in its second term, so the posterior that qφ is trained to approximate is p(θ|x1:N,x*,y*), not the label-free p(θ|x1:N,x*) described in Eq. (3) and Algorithm 1. Algorithm 1 feeds only the context summary and the test embedding into hγ; no y* or label-derived feature is supplied. The Stage 2 objective therefore fits the inference network to a label-conditioned posterior, and the deployment-time uncertainty is an unlabeled evaluation of a posterior whose training target was defined using the very test labels/errors the method claims to flag. The assertion that uncertainty should widen for OOD inputs is thus an artifact of this label conditioning, not a derivation from test covariates alone.
full rationale
The empirical core of the paper—NCC and EF comparisons against an independently trained deep ensemble, PHiSeg, and temperature-scaled variants—is not circular: those numbers are external benchmarks, and temperature scaling is fitted on a held-out adult split. No load-bearing self-citation was found; the VIDS citation [15] is external to the present authors. The circularity sits one level up, in the derivation of the mechanism. Eq. (8) replaces the integral over labels in the original VIDS energy (Eq. (2)) with log p(y*|x*,θ), making the adaptive prior depend on the test label. Algorithm 1 then claims to produce the variational posterior from embeddings alone, without y*. Stage 2 therefore optimizes an inference network to match a label-conditioned posterior p(θ|x1:N,x*,y*) while the deployment-time description promises label-free OOD widening. The central claim that VIDS-Seg's uncertainty 'should occur more frequently for OOD inputs' is not derived from the stated objective; it is a construction-level circularity in which the uncertainty signal is defined through the labels it is supposed to predict. This is partial rather than total circularity because the empirical evaluations remain meaningful observations of the trained system, which is why the score is 6 rather than higher.
Assumptions & free parameters
free parameters (7)
- KL weight lambda_KL =
0.1
- Variance penalty weight tau =
10^-3
- Number of synthetic environments L =
40
- Context set size n =
32
- Posterior samples S =
20
- Temperature T =
fitted per method on adult calibration split
- EF re-derivation exclusion threshold =
5% absolute EF deviation
assumptions (4)
- domain assumption Bootstrap subsamples of adult training data simulate covariate shifts relevant to the adult-to-pediatric shift.
- domain assumption Frozen U-Net embeddings are rich enough for a stochastic 1x1 head to express OOD uncertainty.
- ad hoc to paper The energy function's test term is computable without test labels.
- domain assumption Contour filling and the 5% EF re-derivation filter produce masks that do not bias evaluation.
Cite this review
Pith. "Pith review of VIDS-Seg: Towards Reliable Uncertainty Quantification in Pediatric Cardiac Ultrasound Segmentation." pith.science (2026). https://pith.science/paper/ZRZUKX2X
@misc{pith2026260810903,
author = {Pith},
title = {Pith review of: VIDS-Seg: Towards Reliable Uncertainty Quantification in Pediatric Cardiac Ultrasound Segmentation},
year = {2026},
howpublished = {\url{https://pith.science/paper/ZRZUKX2X}},
note = {Machine review of arXiv:2608.10903}
}
read the original abstract
Reliable clinical deployment of machine learning requires models that know when they are likely to fail, particularly for subgroups underrepresented in training data. A common case is pediatric care, where models trained on adult cohorts can silently under-perform on children with no indication that something has gone wrong. As retraining with labeled pediatric data is often infeasible, detecting such failures at inference time is a critical clinical need. Building on the VIDS (Variational Inference under Distribution Shifts) framework, we introduce VIDS-Seg, which applies amortized variational inference over a lightweight prediction head to make this adaptive, OOD-aware prior tractable for dense image segmentation. We evaluate VIDS-Seg on left ventricular segmentation in echocardiography, a setting where pediatric anatomy differs systematically from the adult population most segmentation models are trained on, training on an adult cohort (EchoNet-Dynamic) and evaluating zero-shot on a pediatric cohort (EchoNet-Pediatric). Across all age strata, VIDS-Seg matches competitive baselines in segmentation accuracy while producing substantially higher spatial correspondence between predicted uncertainty and segmentation error, an advantage that persists even after applying temperature scaling to all baselines. Downstream, it yields more accurate and stable ejection fraction estimates and more reliable detection of cardiac malfunction in the infant subgroup. Our results indicate that OOD-aware uncertainty quantification can serve as a practical safety layer for deployed segmentation models, enabling detection of silent failures in underrepresented subgroups without retraining or additional labeled data.
Figures
Figures from the paper (1 more)
Reference graph
Works this paper leans on
-
[1]
U.S. Food and Drug Administration, Artificial Intelligence and Ma- chine Learning (AI/ML)-Enabled Medical Devices, publicly available database. Data downloaded as a CSV file for analysis. Accessed: 2025- 08-01 (oct 2023)
work page 2025
-
[2]
D. Chatterjee, A. Kanhere, F. X. Doo, J. Zhao, A. Chan, A. Welsh, P. Kulkarni, A. Trang, V. S. Parekh, P. H. Yi, Children are not small adults: addressing limited generalizability of an adult deep learning ct organ segmentation model to the pediatric population, Journal of Imag- ing Informatics in Medicine 38 (3) (2025) 1628–1641
work page 2025
-
[3]
L. Lopez, D. L. Saurers, P. C. Barker, M. S. Cohen, S. D. Colan, J. Dwyer, D. Forsha, M. K. Friedberg, W. W. Lai, B. F. Printz, et al., Guidelines for performing a comprehensive pediatric transtho- racic echocardiogram: recommendations from the american society of echocardiography, Journal of the American Society of Echocardiogra- phy 37 (2) (2024) 119–170
work page 2024
- [4]
-
[5]
V. Muralidharan, A. Burgart, R. Daneshjou, S. Rose, Recommendations fortheuseofpediatricdatainartificialintelligenceandmachinelearning accept-ai, NPJ digital medicine 6 (1) (2023) 166. 22
work page 2023
-
[6]
J. Yang, K. Zhou, Y. Li, Z. Liu, Generalized out-of-distribution de- tection: A survey, International Journal of Computer Vision 132 (12) (2024) 5635–5662
work page 2024
-
[7]
Z. Hong, Y. Yue, Y. Chen, L. Cong, H. Lin, Y. Luo, M. H. Wang, W. Wang, J. Xu, X. Yang, et al., Out-of-distribution detection in med- ical image analysis: A survey, arXiv preprint arXiv:2404.18279 (2024)
arXiv 2024
-
[8]
K. Zou, Z. Chen, X. Yuan, X. Shen, M. Wang, H. Fu, A review of uncertainty estimation and its application in medical imaging, Meta- Radiology 1 (1) (2023) 100003
work page 2023
Show all 32 references
-
[9]
P. K. Han, Uncertainty in Medicine: A Framework for Tolerance, 1st Edition, Oxford University PressNew York, 2021.doi:10.1093/oso/ 9780190270582.001.0001
2021 doi
-
[10]
Lambert, F
B. Lambert, F. Forbes, S. Doyle, A. Tucholka, M. Dojat, Improving uncertainty-based out-of-distribution detection for medical image seg- mentation (2022).arXiv:2211.05421. URLhttps://arxiv.org/abs/2211.05421
2022 arXiv
-
[11]
Ovadia, E
Y. Ovadia, E. Fertig, J. Ren, Z. Nado, D. Sculley, S. Nowozin, J. Dillon, B. Lakshminarayanan, J. Snoek, Can you trust your model’s uncer- tainty? evaluating predictive uncertainty under dataset shift, Advances in neural information processing systems 32 (2019)
2019
-
[12]
A. Wang, T. T. Doan, C. Reddy, P.-N. Jone, Artificial intelligence in fetal and pediatric echocardiography, Children 12 (1) (2024) 14
2024
-
[13]
González, K
C. González, K. Gotkowski, M. Fuchs, A. Bucher, A. Dadras, R. Fis- chbach, I. J. Kaltenborn, A. Mukhopadhyay, Distance-based detection of out-of-distribution silent failures for covid-19 lung lesion segmentation, Medical image analysis 82 (2022) 102596
2022
-
[14]
Lekadir, A
K. Lekadir, A. F. Frangi, A. R. Porras, B. Glocker, C. Cintas, C. P. Langlotz, E. Weicken, F. W. Asselbergs, F. Prior, G. S. Collins, et al., Future-ai: international consensus guideline for trustworthy and deploy- able artificial intelligence in healthcare, bmj 388 (2025)
2025
-
[15]
Slavutsky, D
Y. Slavutsky, D. M. Blei, Quantifying uncertainty in the presence of distribution shifts, arXiv preprint arXiv:2506.18283 (2025). 23
2025
-
[16]
C. F. Baumgartner, K. C. Tezcan, K. Chaitanya, A. M. Hötker, U. J. Muehlematter, K. Schawkat, A. S. Becker, O. Donati, E. Konukoglu, PHiSeg: Capturing uncertainty in medical image segmentation, in: D. Shen, T. Liu, T. M. Peters, L. H. Staib, C. Essert, S. Zhou, P.-T. Yap, A. K...
2019
-
[17]
Lambert, F
B. Lambert, F. Forbes, S. Doyle, H. Dehaene, M. Dojat, Trustworthy clinical ai solutions: a unified review of uncertainty quantification in deep learning models for medical image analysis, Artificial Intelligence in Medicine 150 (2024) 102830
2024
-
[18]
Gonzalez, A
C. Gonzalez, A. Mukhopadhyay, Self-supervised out-of-distribution de- tection for cardiac cmr segmentation, in: Medical Imaging with Deep Learning, PMLR, 2021, pp. 205–218
2021
-
[19]
Mossina, C
L. Mossina, C. Friedrich, Conformal prediction for image segmentation using morphological prediction sets, in: J. C. Gee, D. C. Alexander, J. Hong, J. E. Iglesias, C. H. Sudre, A. Venkataraman, P. Golland, J. H. Kim, J. Park (Eds.), Medical Image Computing and Computer Assiste...
2025
-
[20]
Krueger, E
D. Krueger, E. Caballero, J.-H. Jacobsen, A. Zhang, J. Binas, D. Zhang, R. Le Priol, A. Courville, Out-of-distribution generalization via risk extrapolation (rex), in: International conference on machine learning, PMLR, 2021, pp. 5815–5826
2021
-
[21]
Tran, C.-H
S.-T. Tran, C.-H. Cheng, T.-T. Nguyen, M.-H. Le, D.-G. Liu, Tmd-unet: Triple-unet with multi-scale input features and dense skip connection for medical image segmentation, in: Healthcare, Vol. 9, MDPI, 2021, p. 54
2021
-
[22]
Ouyang, B
D. Ouyang, B. He, A. Ghorbani, N. Yuan, J. Ebinger, C. P. Langlotz, P. A. Heidenreich, R. A. Harrington, D. H. Liang, E. A. Ashley, et al., Video-based ai for beat-to-beat assessment of cardiac function, Nature 580 (7802) (2020) 252–256. 24
2020
-
[23]
C. D. Reddy, L. Lopez, D. Ouyang, J. Y. Zou, B. He, Video-based deep learning for automated assessment of left ventricular ejection fraction in pediatric patients, Journal of the American Society of Echocardiography 36 (5) (2023) 482–489
2023
-
[24]
Bradski, The OpenCV Library, Dr
G. Bradski, The OpenCV Library, Dr. Dobb’s Journal of Software Tools (2000)
2000
-
[25]
Grossgasteiger, M
M. Grossgasteiger, M. D. Hien, B. Graser, H. Rauch, J. Motsch, M. Gon- dan, C. Rosendal, Image quality influences the assessment of left ven- tricular function: an intraoperative comparison of five 2-dimensional echocardiographic methods with real-time 3-dimensional echocardio...
2014
-
[26]
Ronneberger, P
O. Ronneberger, P. Fischer, T. Brox, U-net: Convolutional networks for biomedical image segmentation, in: N. Navab, J. Hornegger, W. M. Wells, A. F. Frangi (Eds.), Medical Image Computing and Computer- Assisted Intervention – MICCAI 2015, Vol. 9351, Springer International Publ...
2015
-
[27]
J. M. Zubler, L. D. Wiggins, M. M. Macias, T. M. Whitaker, J. S. Shaw, J. K. Squires, J. A. Pajek, R. B. Wolf, K. S. Slaughter, A. S. Broughton, et al., Evidence-informed milestones for developmental surveillance tools, Pediatrics 149 (3) (2022) e2021052138
2022
-
[28]
C. Guo, G. Pleiss, Y. Sun, K. Q. Weinberger, On calibration of mod- ern neural networks, in: International conference on machine learning, PMLR, 2017, pp. 1321–1330
2017
-
[29]
T. Akan, S. Alp, M. S. Bhuiyan, T. Helmy, A. W. Orr, M. M. R. Bhuiyan, S. A. Conrad, J. A. Vanchiere, C. G. Kevil, M. A. N. Bhuiyan, Viviechoformer: deep video regressor predicting ejection fraction, Jour- nal of imaging informatics in medicine 38 (4) (2025) 2041–2052
2025
-
[30]
H. J. Shin, N.-H. Son, M. J. Kim, E.-K. Kim, Diagnostic performance of artificial intelligence approved for adults for the interpretation of pe- diatric chest radiographs, Scientific reports 12 (1) (2022) 10215. 25
2022
- [31]
- [32]
Reviewed August 12, 2026 · model on record in the stance chip above.
Discussion (0). Continue with ORCID to comment.