UNIVERS: Learning UNIversal Voxel-wise Embedding via Randomized Synthesis for generalizable one-shot landmark localization

Derong Yu; Qingsong Zhao; Yanbing Yue; Yikai Li; Zhi Zhang; Guoyan Zheng

cs.CVOct 21, 2026

UNIVERS: Learning UNIversal Voxel-wise Embedding via Randomized Synthesis for generalizable one-shot landmark localization

Authors: Derong Yu, Qingsong Zhao, Yanbing Yue, Yikai Li, Zhi Zhang, Guoyan Zheng

Organizations: Institute of Medical Robotics, School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China. · Department of Cardiology, Shanghai General Hospital (originally named Shanghai First People’s Hospital), Shanghai Jiao Tong University School of Medicine, Shanghai 200080, China.

Abstract

One-shot landmark localization in volume scans with varying fields of view (FOVs) is challenging. While existing self-supervised learning methods have shown promising performance, they rely on contrastive learning built upon augmented views of the same image, which inherently limits their generalization in cross-modality scenarios. This motivates research on cross-modality embedding learning using paired multi-modality images. However, existing methods suffer from not only limited training data, but also the requirement of multi-stage iterative training. To address these limitations, we propose UNIVERS, an end-to-end trainable framework that learns UNIversal Voxel-wise Embedding via Randomized Synthesis. Our framework leverages diverse pseudo-data synthesized from organ shape templates, with randomization applied to semantic layout, visual appearance, FOV, and spatial pose. Coupled with cross-domain discriminative voxel-wise contrastive learning, this domain randomization strategy forces the network to disregard domain-specific biases and learn features that are robust against variations in imaging contrast, resolution, and spatial context. Consequently, the trained model enables one-shot landmark localization in multi-modality volume scans with arbitrary FOVs. In this study, the efficacy of the proposed method is demonstrated by applying it to the task of localizing the adrenal glands, which are paired, small, and irregular endocrine organs. In particular, comprehensive experiments are conducted on three challenging adrenal gland datasets. The experimental results demonstrate that UNIVERS consistently outperforms the state-of-the-art (SOTA) one-shot landmark localization approaches, with particularly prominent advantages in cross-modality scenarios. The source code is publicly available at https://github.com/Kendra9999/UNIVERS.

Figures & tables

Fig. 1: A schematic overview of UNIVERS. (a) We construct an image pair database and a patch quadruplet database from shape templates. (b) UNIVERS consists of a shared CNN encoder with a Domain-invariant Discriminative (DD) decoder and a Domain-invariant Semantic (DS) decoder. During training, patch quadruplets are randomly sampled to train the DD decoder via a Cross-domain Discriminative Voxel-wise Contrastive (CDVC) loss, while image pairs are randomly sampled to optimize the DS decoder via a Cross-domain Prototypical Semantic Contrastive (CPSC) loss. (c) During inference, UNIVERS can generate Domain-invariant Voxel-wise (DV) embeddings for multi-modality volumes with arbitrary FOVs. Embeddings are reduced to 3 dimensions via PCA and visualized as RGB images. RGA : Random Geometric Augmentation. Embed. : Embedding.

Fig. 2: Illustration of the coarse-to-fine adrenal gland localization framework built upon a single frozen UNIVERS network. Adrenal gland centers are shown as projections of 3D points along the frontal plane for visualization purposes only. Embeddings are reduced to 3 dimensions via PCA and visualized as RGB images. Embed.: Embedding.

Fig. 3: Visualization of the single support sample for all three one-shot settings. The left two columns respectively display transverse and frontal slices passing through the GT right adrenal gland center points (red circles), while the right two columns show corresponding slices for the left adrenal gland center points (green circles).

Fig. 4: Visual comparison of intra-dataset one-shot adrenal gland localization. The left two columns respectively display transverse and frontal slices passing through the GT or predicted right adrenal gland center points (red circles), while the right two columns show corresponding slices for the left adrenal gland center points (green circles).

Method	${\rm SDR}_{\rm 10}$	${\rm SDR}_{\rm 20}$	${\rm MED}$	$p$ -value
Method	(%) $\uparrow$	(%) $\uparrow$	(mm) $\downarrow$	$p$ -value
Reference Baselines
Lower Bound	55.80	75.45	31.63 $\pm$ 65.29	-
Upper Bound	98.66	99.55	3.04 $\pm$ 13.26	-
One-shot Methods
Affine [ 32 ]	4.91	36.16	35.37 $\pm$ 31.19	$<$ 0.001

TABLE I: Quantitative comparison of intra-dataset one-shot adrenal gland localization. Bold indicates the best results, and underline indicates the second-best results.

\uparrow

indicates higher is better,

\downarrow

indicates lower is better.

Fig. 5: Visual comparison of cross-dataset intra-modality one-shot adrenal gland localization. The left two columns respectively display transverse and frontal slices passing through the GT or predicted right adrenal gland center points (red circles), while the right two columns show those slices for the left adrenal gland center points (green circles).

Method	${\rm SDR}_{\rm 10}$	${\rm SDR}_{\rm 20}$	${\rm MED}$	$p$ -value
Method	(%) $\uparrow$	(%) $\uparrow$	(mm) $\downarrow$	$p$ -value
Reference Baselines
Lower Bound	0.00	0.00	351.56 $\pm$ 106.53	-
Upper Bound	96.59	98.86	3.70 $\pm$ 3.36	-
One-shot Methods
Affine [ 32 ]	9.85	43.18	26.46 $\pm$ 20.89	$<$ 0.001

TABLE II: Quantitative comparison of cross-dataset intra-modality one-shot adrenal gland localization. Bold indicates the best results, and underline indicates the second-best results.

\uparrow

indicates higher is better,

\downarrow

indicates lower is better.

Fig. 6: Visual comparison of cross-dataset cross-modality one-shot adrenal gland localization. The left two columns respectively display transverse and frontal slices passing through the GT or predicted right adrenal gland center points (red circles), while the right two columns show those slices for the left adrenal gland center points (green circles).

Method	${\rm SDR}_{\rm 10}$	${\rm SDR}_{\rm 20}$	${\rm MED}$	$p$ -value
Method	(%) $\uparrow$	(%) $\uparrow$	(mm) $\downarrow$	$p$ -value
Reference Baselines
Lower Bound	0.00	0.22	120.70 $\pm$ 46.76	-
Upper Bound	88.96	97.19	5.56 $\pm$ 6.05	-
One-shot Methods
Affine [ 32 ]	3.46	26.84	30.30 $\pm$ 15.48	$<$ 0.001

TABLE III: Quantitative comparison of cross-dataset cross-modality one-shot adrenal gland localization. Bold indicates the best results, and underline indicates the second-best results.

\uparrow

indicates higher is better,

\downarrow

indicates lower is better.

Model Configuration	Intra-dataset		Cross-dataset Intra-modality		Cross-dataset Cross-modality
Model Configuration	${\rm SDR}_{\rm 10}$ (%) $\uparrow$	${\rm MED}$ (mm) $\downarrow$	${\rm SDR}_{\rm 10}$ (%) $\uparrow$	${\rm MED}$ (mm) $\downarrow$	${\rm SDR}_{\rm 10}$ (%) $\uparrow$	${\rm MED}$ (mm) $\downarrow$
Full Model (Ours)	87.50	6.16 $\pm$ 3.73	78.03	7.46 $\pm$ 4.50	64.72	9.65 $\pm$ 7.61
(a) Ablation on the Pseudo-patch Quadruplet Generation Strategy
Cropping-only	76.34	8.20 $\pm$ 7.43	61.74	11.35 $\pm$ 11.20	58.44	12.34 $\pm$ 11.88
Geometric-augmentation-only	83.48	7.38 $\pm$ 8.17	61.74	12.15 $\pm$ 15.12	54.98	11.03 $\pm$ 8.44
Cropping-and-geometric-augmentation	85.71	6.64 $\pm$ 5.59	68.56	9.70 $\pm$ 9.68	55.84	11.41 $\pm$ 9.12

TABLE IV: Quantitative results of the ablation study on all three one-shot settings. Bold indicates the best results.

\uparrow

indicates higher is better,

\downarrow

indicates lower is better. ”w/o”: without.

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Abstract

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