REVIEW 5 major objections 6 minor 22 references
UNetVL: Enhancing 3D Medical Image Segmentation with Chebyshev KAN Powered Vision-LSTM
T0 review · 5 major / 6 minor · reviewed 2026-08-10 · deepseek-v4-flash
Pith's one-line read The paper claims that UNETVL, a U-Net with a Vision-LSTM encoder and Chebyshev-KAN projections, raises mean Dice by 7.3% on cardiac MRI and 15.6% on abdominal CT versus UNETR, reaching the top compared mean on AMOS.
desk verdict A sensible incremental architecture paper whose headline gains over UNETR are not apples-to-apples, and whose AMOS 'SOTA' gap is within noise; worth refereeing but needs protocol fixes. 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 load-bearing objects are the ViL block pair and the Chebyshev KAN layer. A ViL block alternates forward and backward mLSTM layers, whose matrix-valued memory cell lets the encoder accumulate long-range spatial context over patch tokens with linear cost in sequence length. The Chebyshev KAN layer replaces the MLP in the ViL up and down projections: Chebyshev polynomials $T_0(x)=1$, $T_1(x)=x$, and $T_m(x)=2xT_{m-1}(x)-T_{m-2}(x)$ are combined with a learnable coefficient tensor $C$ of shape $K \times O \times (d+1)$ by Einstein summation to produce the projected feature map. Together they give the encoder long-range memory and the projection paths higher nonlinear capacity.
What would settle it
Train the UNETR baseline and UNETVL with identical data splits, preprocessing, augmentation, batch size, optimizer, and epoch counts, then compare per-fold mean Dice with standard deviations. If the reported 7.3% (ACDC) and 15.6% (AMOS) gaps shrink to roughly 2% or less, the claimed advantage is a protocol artifact rather than an architectural effect.
Extended reading notes
Core claim
On its own terms, the paper's discovery is that a U-Net built from Vision-LSTM encoder blocks, with Chebyshev-KAN projections in place of MLP projections, segments 3D medical volumes more accurately than the ViT-based UNETR it modifies: mean Dice rises from 85.34% to 91.59% on ACDC and from 76.59% to 88.57% on AMOS 2022 post-challenge Task 2, the highest mean among compared methods on the latter. The authors attribute this to bidirectional mLSTM memory capturing long-range spatial context with lower computational cost than self-attention, and to Chebyshev polynomials giving the projection layers stronger nonlinear approximation. They position the model as an efficiency-accuracy alternative to both convolutional and transformer encoders, with the network architecture as the only variable in an otherwise standardized pipeline.
Load-bearing premise
The load-bearing assumption is that the published UNETR and other comparison scores were obtained under the same preprocessing, training, and evaluation protocol as UNETVL, so the reported Dice gains reflect the architecture rather than the pipeline.
Editorial extensions
If this is right
- A ViL-based encoder gives a transformer-free way to model long-range spatial dependencies in 3D volumes with linear rather than quadratic complexity.
- Chebyshev KAN projections can be swapped into ViL up and down projection layers with a one-line change, raising Dice in the reported settings.
- On the AMOS 2022 post-challenge Task 2 dataset, the architecture reaches the highest mean Dice among compared methods, supporting abdominal multi-organ segmentation.
- The ablations show that raising the latent dimension $K$ improves accuracy at higher parameter counts, giving an explicit accuracy-cost trade-off for deployment.
Reading between the lines
- Because several comparison-table baselines were taken from a prior study rather than rerun here, the 7.3% and 15.6% gains should be read as provisional until a same-protocol head-to-head confirms them.
- The Chebyshev-versus-MLP advantage was isolated in a lightweight segmentation model on ACDC; whether it transfers to other organs, modalities, or full UNETVL scales is untested.
- ViL's linear complexity suggests the encoder could be pushed to larger patch counts or higher input resolutions than the tested settings.
- The qualitative over-segmentation reduction could be made quantitative with surface Dice or Hausdorff distance, which would strengthen the clinical claim.
Signed reviews
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper proposes UNETVL, a 3D medical image segmentation architecture that replaces the ViT encoder of UNETR with Vision-LSTM (ViL) blocks and injects Chebyshev KAN layers into the up- and down-projection paths. The method is implemented inside the nnU-Net framework and evaluated on the ACDC and AMOS 2022 post-challenge Task 2 datasets. The authors report mean Dice scores of 91.59 on ACDC and 88.57 on AMOS, claim improvements of 7.3% and 15.6% over UNETR, and state that the AMOS result is the highest among the compared methods. Ablation studies on the ACDC dataset are used to justify the Chebyshev KAN choice and the latent dimension.
Significance. If the reported results hold under uniform evaluation, the paper would present a strong and practical 3D segmentation backbone, with the code release and the nnU-Net-based implementation being concrete strengths. However, the central quantitative claims are currently not established because the UNETR baseline is taken from an external study with a different protocol, and the AMOS state-of-the-art claim rests on a 0.55-point margin without any uncertainty quantification. The architecture itself is plausible, and the within-pipeline comparisons against SwinUNETR and other modern baselines are informative, but the headline deltas and the SOTA designation need more rigorous support before the paper can be accepted.
major comments (5)
- [Section 3, Implementation Details; Table 1] The claim that the nnU-Net framework 'ensures a fair comparison ... with the network architecture as the sole variable' is not true for the UNETR baseline. Table 1's caption states that all results except UNETR and SAM3D come from the nnU-Net revisited study, while UNETVL is trained using nnU-Net preprocessing, augmentation, oversampling, and 5-fold evaluation. The UNETR Dice scores (85.34 on ACDC, 76.59 on AMOS) are legacy numbers from the original UNETR paper, which used a different protocol. Consequently, the 7.3% and 15.6% improvements advertised in the abstract are cross-protocol comparisons and may be artifacts of preprocessing or training differences rather than architectural superiority. The authors should rerun UNETR inside the nnU-Net pipeline, or explicitly state that the UNETR comparison is not apples-to-apples and remove the quantitative improvement claims from the abstract.
- [Section 4, Table 1] The claim that UNETVL 'achieves the highest mean Dice score on the AMOS 2022 post-challenge Task 2 dataset' is not statistically supported. The margin over CoTr is only 0.55 percentage points (88.57 vs. 88.02), yet no per-fold results, standard deviations, confidence intervals, or significance tests are reported anywhere in the paper. With 5-fold cross-validation, a difference of this size can easily arise from fold-to-fold variability. The authors should report per-fold scores and some measure of uncertainty before making a SOTA claim.
- [Section 4, Table 2] The ablation table is presented without clarifying that it uses a different evaluation protocol than the final results: the caption says 'test on ACDC cross validation fold 1 after 100 epochs', whereas Table 1 reports 5-fold cross-validation results. As a result, the reader cannot directly compare the ablation numbers (e.g., 89.79 for w/ KAN, K=384 in Table 2) with the main result (91.59 in Table 1), and the conclusion that 'increasing the latent dimension results in better segmentation' is only supported on a single fold after 100 epochs. The authors should either run the full ablation over all 5 folds and the full training schedule, or explicitly state that the ablation is preliminary and only indicative.
- [Section 4, Choice of Univariate Functions for KAN] The selection of Chebyshev polynomials as the univariate function in the KAN layer is made using 5-fold cross-validation on the ACDC dataset, and the final UNETVL model is then evaluated on the same ACDC benchmark. This creates a selection bias: the function choice is tuned to ACDC and the reported ACDC performance of the full model is not an unbiased estimate. Moreover, the difference between Chebyshev (86.12) and MLP (85.88) in Table 3 is only 0.24 percentage points, and no error bars are provided. The paper's claim that Chebyshev 'consistently demonstrated superior performance' is therefore not firmly established. The authors should report the variance of these estimates, evaluate the function choice on a held-out dataset (e.g., AMOS), or temper the claim.
- [Throughout; Sections 3 and 4] No error bars, standard deviations, or statistical significance tests are provided for any of the main segmentation results. Given that the paper's central claims include a 7.3% improvement on ACDC and a 0.55-point SOTA margin on AMOS, the absence of uncertainty quantification is a load-bearing omission. The authors should report per-fold Dice scores and at least the standard deviation across folds for all methods they compare, especially for their own model.
minor comments (6)
- [Section 2.3, Eq. (1)] The tensor T is defined as having shape R^{N x K x (degree+1)}, and the summation is written over i and j, but the index j is not explicitly defined in the text as the polynomial-degree index; please add a sentence for clarity.
- [Section 2.2] The description of the mLSTM block would benefit from equations or a precise pointer to the xLSTM paper; as written, the memory-cell mechanism is described only verbally, which makes the architecture hard to reproduce from the paper alone.
- [Figure 1] The right panel of Figure 1 is low-contrast and the labels 'Even', 'False', 'Flip', and the KAN projection annotations are difficult to read; please enlarge the figure or split it into separate panels.
- [Table 3] There is a formatting issue: the caption appears as 'Table 3 .' and the table body is not well spaced; also, the rows for MLP, B-Spline, Gaussian RBF, and Chebyshev should be visually separated.
- [Section 5, Discussion] The statement that UNETVL 'significantly mitigates over-segmentation' is not quantified; Figure 2 shows qualitative examples, but a quantitative measure such as boundary F1, surface Dice, or a per-structure over-segmentation metric would support the claim.
- [Throughout] The paper uses both 'Kolmogorov–Arnold Networks (KAN)' and 'Kolmogorov-Arnold Network' inconsistently; please unify the terminology and check singular/plural usage.
Circularity Check
No significant circularity: the architecture's claims are empirical and its components are cited from external work, not derived from the target result.
full rationale
UNETVL is an empirical architecture paper. The ViL encoder and Chebyshev KAN layers are adopted from external prior work (references [3,4,5,9]) and are not derived from the ACDC or AMOS Dice scores. The reported Dice values are measured outcomes, not quantities solved for from the definition of the model. Table 1's UNETR baseline is imported from the original UNETR study rather than re-run inside the nnU-Net pipeline, and the Chebyshev activation is selected via ACDC cross-validation before final ACDC reporting; both are protocol and selection concerns that could affect the validity of the comparison, but neither makes a prediction equivalent to its input by construction. There are no load-bearing self-citations, no fitted parameter renamed as a prediction, and no uniqueness theorem imported from the authors. Under the hard rules, such concerns belong to correctness risk, not circularity, so the circularity score is 0.
Assumptions & free parameters
free parameters (3)
- Embedding dimension K =
384
- Chebyshev polynomial degree =
Not reported
- Number of ViL block pairs per stage =
Not reported
assumptions (3)
- domain assumption Vision-LSTM as described by Alkin et al. (2024) provides a valid and effective backbone when adapted to 3D patch tokens.
- domain assumption The nnU-Net framework's preprocessing, augmentation, and training schedule are appropriate for all compared architectures.
- ad hoc to paper Chebyshev polynomial basis functions can represent the needed feature transformations at least as well as MLPs.
Cite this review
Pith. "Pith review of UNetVL: Enhancing 3D Medical Image Segmentation with Chebyshev KAN Powered Vision-LSTM." pith.science (2026). https://pith.science/paper/MVJM4L32
@misc{pith2026250107017,
author = {Pith},
title = {Pith review of: UNetVL: Enhancing 3D Medical Image Segmentation with Chebyshev KAN Powered Vision-LSTM},
year = {2026},
howpublished = {\url{https://pith.science/paper/MVJM4L32}},
note = {Machine review of arXiv:2501.07017}
}
read the original abstract
3D medical image segmentation has progressed considerably due to Convolutional Neural Networks (CNNs) and Vision Transformers (ViTs), yet these methods struggle to balance long-range dependency acquisition with computational efficiency. To address this challenge, we propose UNETVL (U-Net Vision-LSTM), a novel architecture that leverages recent advancements in temporal information processing. UNETVL incorporates Vision-LSTM (ViL) for improved scalability and memory functions, alongside an efficient Chebyshev Kolmogorov-Arnold Networks (KAN) to handle complex and long-range dependency patterns more effectively. We validated our method on the ACDC and AMOS2022 (post challenge Task 2) benchmark datasets, showing a significant improvement in mean Dice score compared to recent state-of-the-art approaches, especially over its predecessor, UNETR, with increases of 7.3% on ACDC and 15.6% on AMOS, respectively. Extensive ablation studies were conducted to demonstrate the impact of each component in UNETVL, providing a comprehensive understanding of its architecture. Our code is available at https://github.com/tgrex6/UNETVL, facilitating further research and applications in this domain.
Figures
Reference graph
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INTRODUCTION The incorporation of artificial intelligence (AI) into medi- cal image process has profoundly revolutionized patient care, providing a more efficient and accessible approach to im- proving diagnostic precision and prognostic outcomes. Accu- rate segmentation, in particular, acts as a fundamental step in biomedical image analysis, delineating ...
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Architecture Overview We present the overall architecture of our UNETVL model in Fig
METHODOLOGY 2.1. Architecture Overview We present the overall architecture of our UNETVL model in Fig. 1. Building upon the UNETR structure [1], UNETVL employs an encoder-decoder network that efficiently captures both local features and long-range contexts. The model pro- cesses a 3D oversampled instance with resolution (H, W, D) and C input channels, app...
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EXPERIMENTS Datasets. We evaluate the effectiveness of our approach on two public 3D segmentation benchmarks, both involving mul- tiple structures or multiple organs: the Automated Cardiac Linear Projection 1 2 3 4 5 6 7 8 9 Embedded Patches + ViL Block Pairs Stage 2 ViL Block Pairs Stage 1 ViL Block Pairs Stage 3 ViL Block Pairs Stage 4 UNETR Decoder Lay...
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RESULTS Evaluation on ACDC and AMOS. As shown in Table 1, when comparing the performance of the ViL architecture with Chebyshev KAN to the UNETR baseline, a signifi- cant improvement is observed. On the ACDC dataset, the Dice score improves by approximately 7.3% (from 85.34% in UNETR to 91.59% in UNETVL with KAN). Similarly, for the AMOS dataset, the Dice...
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DISCUSSION AND CONCLUSION The proposed UNETVL architecture, enhanced by Cheby- shev KAN, demonstrates competitive performance in 3D medical image segmentation tasks. While the Dice score may not be the absolute highest, the model significantly mitigates over-segmentation, capturing finer anatomical de- Model Configuration #Params (M) Mean Dice Score (%) w...
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COMPLIANCE WITH ETHICAL STANDARDS This research study was conducted retrospectively using hu- man subject data made available in open access by Bernard et al. [6] and Ji et al. [7]. Ethical approval was not required as confirmed by the license attached with the open access data
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Reviewed August 10, 2026 · model on record in the stance chip above.
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