REVIEW 4 major objections 6 minor 42 references
Novel Extraction of Discriminative Fine-Grained Feature to Improve Retinal Vessel Segmentation
T0 review · 4 major / 6 minor · reviewed 2026-08-15 · deepseek-v4-flash
Pith's one-line read The paper claims that AttUKAN, a U-shaped Kolmogorov-Arnold network with attention-gated skip connections and a label-guided pixel-wise contrastive loss, extracts more discriminative encoder features and reports the highest F1 and MIoU…
desk verdict A workmanlike combination of known components with broad but unverified ablations; the MIoU formula as printed contradicts every reported table. 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 machinery is two additions to a U-shaped Kolmogorov-Arnold Network (KAN). First, Attention Gates in the skip connections compute a gating coefficient from the encoder feature and a higher-level gating signal, multiply the feature map elementwise, and suppress irrelevant activations before concatenation with the decoder. Second, the Label-guided Pixel-wise Contrastive Loss (LPCL) samples pixel-level feature vectors from the bottleneck feature map; pairs of pixels with the same ground-truth class are positives and different-class pairs are negatives, and a contrastive objective pulls same-class vectors together and pushes different-class vectors apart in representation space. The KAN blocks themselves replace linear layers with learnable nonlinear activation functions, giving the encoder more nonlinear modeling capacity.
What would settle it
Retrain AttUKAN and the 11 baselines under one fixed public protocol (same splits, same preprocessing, several random seeds) on DRIVE, STARE, and CHASE_DB1, then compare each method's F1 mean and standard deviation; if AttUKAN's lead over the second-best method is smaller than the seed-to-seed spread, the reported advantage would fall within training noise.
Extended reading notes
Core claim
The central claim is that feature-level supervision is the missing ingredient in retinal vessel segmentation. Existing models train primarily by comparing decoder output with ground-truth labels, but AttUKAN applies a contrastive loss directly to the bottleneck feature map, using the label to define positive pairs (same class) and negative pairs (different classes). Attention gates in skip connections suppress irrelevant activations so finer vessel structure is retained. The paper reports F1 scores of 82.50%, 81.14%, 81.34%, 80.21%, and 80.09% and MIoU scores of 70.24%, 68.64%, 68.59%, 67.21%, and 66.94% across the five datasets, each the highest among the 11 baselines, and ablation studies attribute the gains to both the attention gates and LPCL.
Load-bearing premise
The comparison assumes every one of the 12 methods is trained and evaluated under identical splits, preprocessing, and hyperparameter settings, and that the reported single-run differences of about 0.1 to 1.0 F1 points reflect real model differences rather than training noise.
Editorial extensions
If this is right
- If AttUKAN's results hold, feature-level contrastive supervision at the bottleneck is an effective complement to decoder-level losses for retinal vessel segmentation.
- The ablations show LPCL also improves several existing U-Net style baselines when added to them, suggesting the loss transfers beyond the proposed architecture.
- Attention-gated skip connections on a KAN backbone may generalize to other fine-structure segmentation tasks where thin structures dominate.
- The reported gains on high-resolution datasets (HRF and the private set) indicate the approach works outside the small-patch regime.
- The reported F1 and MIoU numbers, if reproducible, establish new quantitative baselines for these five datasets.
Reading between the lines
- Because LPCL is applied only at the bottleneck, one could test whether applying it at multiple decoder levels further improves small vessel tips; the paper does not explore this.
- The method uses label-guided pixel pairs rather than heavy augmentation or large contrastive batches, which may make it easier to adopt when training data are scarce.
- A direct probe of feature-map cluster purity (vessel vs background) could test whether LPCL's mechanism is indeed better feature separability and whether it correlates with F1 gain.
- When the private dataset is released, external groups can check whether the advantage persists under an independent evaluation protocol.
Signed reviews
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper proposes AttUKAN, a U-shaped Kolmogorov-Arnold Network with Attention Gates placed on skip connections, and a Label-guided Pixel-wise Contrastive Loss (LPCL) to improve retinal vessel segmentation. The method is evaluated on DRIVE, STARE, CHASE_DB1, HRF, and a private dataset, with F1 and MIoU reported as the primary metrics. The authors claim state-of-the-art results against 11 baseline networks across all five datasets, and support the claim with ablation studies on the network components, loss terms, the LPCL weighting coefficient, the feature level used for LPCL, and the transferability of LPCL to other architectures.
Significance. If the results are validated, the paper offers a practical and portable improvement: attention-gated KAN blocks plus a supervised contrastive loss that also improves several existing U-shaped networks. The study is unusually broad in its evaluation, covering five datasets and multiple ablations, and the transfer experiment of LPCL across architectures is a genuine strength. However, the central quantitative claim is currently undermined by an internally inconsistent metric definition, a complete absence of statistical uncertainty, and an unclear statement of the spatial resolution at which LPCL operates. The reported F1 gains over the best baselines are small (0.07 to 0.54 percentage points), so without error bars or significance testing the 'highest compared to 11 networks' claim is not yet demonstrated. The paper ships no code and gives no experimental logs, further limiting verification.
major comments (4)
- [Section 4.2, Eq. (20)] The definition of MIoU is internally inconsistent with all reported results. Equation (19) defines F1 = 2TP/(2TP+FP+FN) and Eq. (20) defines MIoU = 2TP/(TP+FP+FN). Since 2TP+FP+FN > TP+FP+FN for any non-degenerate confusion matrix, Eq. (20) forces MIoU > F1 in every row, yet every entry of Tables 2–7 shows the opposite. For example, DRIVE AttUKAN reports F1=82.50% and MIoU=70.24%; combining Eqs. (19) and (20) algebraically gives MIoU = 2F1/(2−F1) = 140.4% for F1=82.50%, not 70.24%. The reported MIoU values are numerically consistent with the standard foreground IoU, TP/(TP+FP+FN): for F1=82.50%, IoU=82.50/(200−82.50)=70.21%, matching 70.24% up to rounding. The formula must be corrected (most plausibly to TP/(TP+FP+FN)) or the reported MIoU values cannot be reproduced. Because the abstract and Section 4.4 base the SOTA claim jointly on F1 and MIoU, this is a load-bearing defect.
- [Section 4.4, Tables 2–6] No variance, error bars, or statistical significance tests are reported. The F1 advantages over the best baseline are 0.22 points on DRIVE, 0.15 on STARE, 0.54 on CHASE_DB1, 0.07 on HRF, and 0.11 on the private dataset, while the component ablations in Table 8 improve F1 by 0.10 to 0.75 points. With a single run and no reported seeds, these differences could easily fall within training noise. Please provide mean and standard deviation over at least three random seeds, or an equivalent paired statistical test, for the main comparisons and the ablations, so the claimed superiority can be distinguished from stochastic variation.
- [Section 3.4 and Section 4.3] LPCL is computed on the 5th-level bottleneck feature of size S×S. With the stated patch size of 64×64 and the 32× downsampling at the bottleneck shown in Figure 2, S=2, so only four spatial positions per image are available as anchors. This is at odds with the description of a 'pixel-wise' contrastive loss for fine-grained representations. The paper does not specify how the ground-truth label is mapped to the 2×2 feature grid, nor how the positive set Ω+_i is constructed across the S×S positions and across the two random augmentations. Please clarify the actual feature resolution, the label downsampling procedure, and the positive-pair construction; if S=2, justify how such a coarse spatial loss provides fine-grained supervision.
- [Section 4.4, baseline comparisons] The paper asserts that 'all experiments across different methods utilize the same dataset settings and partitions,' but it does not state whether the baseline results in Tables 2–6 are re-implemented by the authors or cited from the original papers, and no code is provided. The STARE/CHASE_DB1 split (first 10/14 images for training) is nonstandard, and the private dataset is not publicly available. Without experimental logs or code, the reader cannot verify that the small F1/MIoU gains are not artifacts of differing preprocessing, split, or training protocols. Please specify the provenance of each baseline number and release code or detailed configuration files for all experiments.
minor comments (6)
- [Table 11] The 3rd-level-feature row for STARE reports MIoU=88.25% and AUC=88.25%, values that are mathematically incompatible with F1=81.04% under either MIoU definition and that deviate sharply from the other rows; these appear to be data-entry errors and should be corrected.
- [Eq. (11)] The LPCL loss is not fully specified: the outer factor appears to be printed as '2N' but is likely intended to be '1/(2N)', and the construction of Ω+_i relative to the two augmentations X~2i and X~2i−1 is not defined explicitly.
- [Section 3.4] The sentence 'For every two input images, we can form S² pixel-level contrastive pairs' does not match the loss formula, which sums over anchors s and positives j; the relationship between the number of pairs and the anchor/positive sets should be clarified.
- [Figures 2 and 3] The two versions of Figure 3 use inconsistent loss labels ('Dice + BCE Loss' versus 'Dice + Jaccard + BCE Loss'), and Figure 3(c) contains a subscript typo in the activation notation (ReLu(σ1) versus ReLU(σ2)).
- [Section 4.2, Eq. (15)] The Hausdorff distance formula has an unbalanced parenthesis in the quantile expressions, making the definition ambiguous.
- [Section 4.1, private dataset] The private dataset is a core part of the five-dataset SOTA claim but is not publicly available; please add a supplementary data sheet or an explicit availability statement describing the acquisition, annotation, and ethical approval details.
Circularity Check
No circularity: AttUKAN and LPCL are trained end-to-end and evaluated on test data; the MIoU formula inconsistency is an internal metric-definition bug, not a circular reduction.
full rationale
The paper's central claims are empirical evaluations of a trained segmentation network. The architecture (Attention Gates plus tokenized KAN blocks) and the Label-guided Pixel-wise Contrastive Loss are defined in Section 3 from external building blocks (KAN, UNet, additive attention) and are optimized end-to-end on labeled fundus images; there is no fitted constant that is subsequently renamed as a prediction. The loss weights lambda_1..lambda_3 are taken from prior work and lambda_4 is chosen by ablation (Tables 8-10); this is standard hyperparameter selection, and although per-dataset selection from an ablation sweep is a possible overfitting risk, it does not make the reported F1/MIoU numbers equivalent to the loss definition by construction. The references to KAN [16] and UKAN [17] are independent prior work, not self-citations, and no uniqueness theorem is invoked. The only notable defect is formal: Eq. (20) defines MIoU = 2TP/(TP+FP+FN), which would always exceed F1 = 2TP/(2TP+FP+FN), while all tables report F1 > MIoU; the reported values match the standard IoU definition. This is an internal metric inconsistency that undermines reproducibility of the MIoU claim, but it is not a circular derivation: the tabulated numbers remain measurements, not consequences of the definition. Therefore no circularity is found.
Assumptions & free parameters
free parameters (3)
- lambda_4 (LPCL weight) =
0.3 for DRIVE/STARE/CHASE_DB1; 0.5 for HRF/private (Table 10)
- lambda_1, lambda_2, lambda_3 loss weights =
0.8, 0.2, 1.0
- patch size, batch size, learning rate, epochs =
64x64, 25, 0.003, 100
assumptions (3)
- domain assumption STARE and CHASE_DB1 are split first-10/first-14 for training per DUNet [7]; HRF 30/15; private 90/25.
- domain assumption The 11 baseline methods were re-implemented or run with the same preprocessing pipeline.
- domain assumption Augmented views for LPCL (tilde X_2i and tilde X_2i-1) both share the same ground truth label map.
Cite this review
Pith. "Pith review of Novel Extraction of Discriminative Fine-Grained Feature to Improve Retinal Vessel Segmentation." pith.science (2026). https://pith.science/paper/NLLBUCNZ
@misc{pith2026250503896,
author = {Pith},
title = {Pith review of: Novel Extraction of Discriminative Fine-Grained Feature to Improve Retinal Vessel Segmentation},
year = {2026},
howpublished = {\url{https://pith.science/paper/NLLBUCNZ}},
note = {Machine review of arXiv:2505.03896}
}
read the original abstract
Retinal vessel segmentation is a vital early detection method for several severe ocular diseases. Despite significant progress in retinal vessel segmentation with the advancement of Neural Networks, there are still challenges to overcome. Specifically, retinal vessel segmentation aims to predict the class label for every pixel within a fundus image, with a primary focus on intra-image discrimination, making it vital for models to extract more discriminative features. Nevertheless, existing methods primarily focus on minimizing the difference between the output from the decoder and the label, but ignore fully using feature-level fine-grained representations from the encoder. To address these issues, we propose a novel Attention U-shaped Kolmogorov-Arnold Network named AttUKAN along with a novel Label-guided Pixel-wise Contrastive Loss for retinal vessel segmentation. Specifically, we implement Attention Gates into Kolmogorov-Arnold Networks to enhance model sensitivity by suppressing irrelevant feature activations and model interpretability by non-linear modeling of KAN blocks. Additionally, we also design a novel Label-guided Pixel-wise Contrastive Loss to supervise our proposed AttUKAN to extract more discriminative features by distinguishing between foreground vessel-pixel pairs and background pairs. Experiments are conducted across four public datasets including DRIVE, STARE, CHASE_DB1, HRF and our private dataset. AttUKAN achieves F1 scores of 82.50%, 81.14%, 81.34%, 80.21% and 80.09%, along with MIoU scores of 70.24%, 68.64%, 68.59%, 67.21% and 66.94% in the above datasets, which are the highest compared to 11 networks for retinal vessel segmentation. Quantitative and qualitative results show that our AttUKAN achieves state-of-the-art performance and outperforms existing retinal vessel segmentation methods. Our code will be available at https://github.com/stevezs315/AttUKAN.
Reference graph
Works this paper leans on
-
[1]
Thomas J Smart, Christopher J Richards, Rhythm Bhat- nagar, Carlos Pavesio, Rupesh Agrawal, Philip H Jones, in Optical trapping and optical micromanipulation XII, SPIE,2015, pp. 342–348
work page 2015
-
[2]
Jie Ding, Khin Lay Wai, Kevin McGeechan, M Kam- ran Ikram, Ryo Kawasaki, Jing Xie, Ronald Klein, Bar- baraBKKlein,MaryFrancesCotch,JieJinWang,etal., Journal of hypertension2014, 32 (2), 207–215
-
[3]
Tong Na, Jianyang Xie, Yitian Zhao, Yifan Zhao, Yue Liu, Yongtian Wang, Jiang Liu,Medical physics2018, 45 (7), 3132–3146
-
[4]
Zhe Han, Yilong Yin, Xianjing Meng, Gongping Yang, XiaoweiYan,in 2014IEEEInternationalConferenceon Data Mining Workshop, IEEE,2014, pp. 960–967
work page 2014
- [5]
-
[6]
Olaf Ronneberger, Philipp Fischer, Thomas Brox, in Medical image computing and computer-assisted intervention–MICCAI 2015: 18th international confer- ence, Munich, Germany, October 5-9, 2015, proceed- ings, part III 18, Springer,2015, pp. 234–241. 14 Shuang ZengET AL
work page 2015
-
[7]
Qiangguo Jin, Zhaopeng Meng, Tuan D Pham, Qi Chen, LeyiWei,RanSu, Knowledge-BasedSystems 2019,178, 149–162
work page 2019
-
[8]
Yaolei Qi, Yuting He, Xiaoming Qi, Yuan Zhang, Guanyu Yang, inProceedings of the IEEE/CVF Interna- tional Conference on Computer Vision, 2023, pp. 6070– 6079
work page 2023
Show all 42 references
-
[9]
3656–3665
Liangzhi Li, Manisha Verma, Yuta Nakashima, Hajime Nagahara, Ryo Kawasaki, in Proceedings of the IEEE/CVF winter conference on applications of computer vision, 2020, pp. 3656–3665
2020
-
[10]
1237– 1241
KunWang,XiaohongZhang,ShengHuang,QiuliWang, FeiyuChen,in 2020IEEE17thInternationalSymposium on Biomedical Imaging (ISBI), IEEE,2020, pp. 1237– 1241
2020
-
[11]
Reza Azad, Maryam Asadi-Aghbolaghi, Mahmood Fathy, Sergio Escalera, inProceedings of the IEEE/CVF international conference on computer vision workshops, 2019, pp. 0–0
2019
-
[12]
Ozan Oktay, Jo Schlemper, Loic Le Folgoc, Matthew Lee,MattiasHeinrich,KazunariMisawa,KensakuMori, Steven McDonagh, Nils Y Hammerla, Bernhard Kainz, et al.,arXiv preprint arXiv:1804.039992018
-
[13]
Zongwei Zhou, Md Mahfuzur Rahman Siddiquee, Nima Tajbakhsh, Jianming Liang, inDeep Learning in Medi- calImageAnalysisandMultimodalLearningforClinical Decision Support: 4th International Workshop, DLMIA 2018, and 8th International Workshop, ML-CDS 2018, Held in Conjunction with...
2018
-
[14]
3819–3827
Yutong Liu, Haijiang Zhu, Mengting Liu, Huaiyuan Yu, ZihanChen,JieGao,in ProceedingsoftheAAAIConfer- ence on Artificial Intelligence, 2024, pp. 3819–3827
2024
-
[15]
Ziyang Wang, Jian-Qing Zheng, Yichi Zhang, Ge Cui, Lei Li,arXiv preprint arXiv:2402.050792024
-
[16]
Ziming Liu, Yixuan Wang, Sachin Vaidya, Fabian Ruehle, James Halverson, Marin Soljačić, Thomas Y Hou, Max Tegmark,arXiv preprint arXiv:2404.19756 2024
2024 arXiv
-
[17]
Chenxin Li, Xinyu Liu, Wuyang Li, Cheng Wang, Hengyu Liu, Yixuan Yuan, arXiv preprint arXiv:2406.029182024
-
[18]
1597–1607
Ting Chen, Simon Kornblith, Mohammad Norouzi, GeoffreyHinton,in Internationalconferenceonmachine learning, PMLR,2020, pp. 1597–1607
2020
-
[19]
9729–9738
Kaiming He, Haoqi Fan, Yuxin Wu, Saining Xie, Ross Girshick, in Proceedings of the IEEE/CVF conference on computer vision and pattern recognition, 2020, pp. 9729–9738
2020
-
[20]
1166–1170
Nagendra Pratap Singh, Rajesh Kumar, Rajeev Srivas- tava, inInternational Conference on Computing, Com- munication & Automation, IEEE,2015, pp. 1166–1170
2015
-
[21]
Frederic Zana, J-C Klein,IEEE transactions on image processing2001, 10 (7), 1010–1019
-
[22]
Wendeson S Oliveira, Joyce Vitor Teixeira, Tsang Ing Ren, George DC Cavalcanti, Jan Sijbers,PloS one2016, 11 (2), e0149943
-
[23]
Huazhu Fu, Yanwu Xu, Stephen Lin, Damon Wing Kee Wong, Jiang Liu, in Medical Image Comput- ing and Computer-Assisted Intervention–MICCAI 2016: 19th International Conference, Athens, Greece, October 17-21,2016,Proceedings,PartII19 ,Springer, 2016,pp. 132–139
2016
-
[24]
Yanfei Guo, Yanjun Peng,BMC medical imaging2020, 20, 1–22
-
[25]
Seung Yeon Shin, Soochahn Lee, Il Dong Yun, Kyoung Mu Lee, Medical image analysis 2019, 58, 101556
2019
-
[26]
Yinda Chen, Haoyuan Shi, Xiaoyu Liu, Te Shi, Ruob- ing Zhang, Dong Liu, Zhiwei Xiong, Feng Wu,arXiv preprint arXiv:2405.168472024
-
[27]
AlexeyDosovitskiy,LucasBeyer,AlexanderKolesnikov, Dirk Weissenborn, Xiaohua Zhai, Thomas Unterthiner, Mostafa Dehghani, Matthias Minderer, Georg Heigold, Sylvain Gelly, et al.,arXiv preprint arXiv:2010.11929 2020
2010 arXiv
-
[28]
Jinming Cao, Yangyan Li, Mingchao Sun, Ying Chen, Dani Lischinski, Daniel Cohen-Or, Baoquan Chen, Changhe Tu, IEEE Transactions on Image Processing 2022, 31, 3726–3736
2022
-
[29]
Jimmy Lei Ba, Jamie Ryan Kiros, Geoffrey E Hinton, arXiv preprint arXiv:1607.064502016
-
[30]
Dzmitry Bahdanau, Kyunghyun Cho, Yoshua Bengio, arXiv preprint arXiv:1409.04732014
-
[31]
Joes Staal, Michael D Abràmoff, Meindert Niemeijer, Max A Viergever, Bram Van Ginneken,IEEE transac- tions on medical imaging2004, 23 (4), 501–509
-
[32]
Shuang ZengET AL 15
ADHoover,ValentinaKouznetsova,MichaelGoldbaum, IEEE Transactions on Medical imaging2000, 19 (3), 203–210. Shuang ZengET AL 15
-
[33]
ChristopherGOwen,AlicjaRRudnicka,RobertMullen, SarahABarman,DorothyMonekosso,PeterHWhincup, JeffreyNg,CarlPaterson, Investigativeophthalmology& visual science2009, 50 (5), 2004–2010
2004
-
[34]
Jan Odstrcilik, Radim Kolar, Attila Budai, Joachim Hornegger, Jiri Jan, Jiri Gazarek, Tomas Kubena, Pavel Cernosek, Ondrej Svoboda, Elli Angelopoulou, IET Image Processing2013, 7 (4), 373–383
-
[35]
Manuel Emilio Gegúndez-Arias, Arturo Aquino, José Manuel Bravo, Diego Marín,IEEE transactions on medical imaging2011, 31 (2), 231–239
-
[36]
Bo Wang, Shuang Qiu, Huiguang He, in Medical Image Computing and Computer Assisted Intervention– MICCAI 2019: 22nd International Conference, Shen- zhen, China, October 13–17, 2019, Proceedings, Part I 22, Springer,2019, pp. 84–92
2019
-
[37]
6077–6086
Peter Anderson, Xiaodong He, Chris Buehler, Damien Teney,MarkJohnson,StephenGould,LeiZhang,in Pro- ceedingsoftheIEEEconferenceoncomputervisionand pattern recognition, 2018, pp. 6077–6086
2018
-
[38]
Saumya Jetley, Nicholas A Lord, Namhoon Lee, Philip HS Torr,arXiv preprint arXiv:1804.023912018
-
[39]
7132–7141
Jie Hu, Li Shen, Gang Sun, inProceedings of the IEEE conference on computer vision and pattern recognition, 2018, pp. 7132–7141
2018
-
[40]
Sanghyun Woo, Jongchan Park, Joon-Young Lee, In So Kweon, inProceedings of the European conference on computer vision (ECCV), 2018, pp. 3–19
2018
-
[41]
João VB Soares, Jorge JG Leandro, Roberto M Cesar, HerbertFJelinek,MichaelJCree, IEEETransactionson medical Imaging2006, 25 (9), 1214–1222
-
[42]
Stephen M Pizer, E Philip Amburn, John D Austin, Robert Cromartie, Ari Geselowitz, Trey Greer, Bart ter Haar Romeny, John B Zimmerman, Karel Zuiderveld, Computer vision, graphics, and image processing1987, 39 (3), 355–368. 16 Shuang ZengET AL RollingUNetUNet UNet++ UKAN DSCNet...
Reviewed August 15, 2026 · model on record in the stance chip above.
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