Author name cluster

Nicolas Padoy

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7 papers

2 author rows

AAAI Conference 2026 Conference Paper

Where It Moves, It Matters: Referring Surgical Instrument Segmentation via Motion

Meng Wei
Kun Yuan
Shi Li
Yue Zhou
Long Bai
Nassir Navab
Hongliang Ren
Hong Joo Lee

Enabling intuitive, language-driven interaction with surgical scenes is a critical step toward intelligent operating rooms and autonomous surgical robotic assistance. However, the task of referring segmentation, localizing surgical instruments based on natural language descriptions, remains underexplored in surgical videos, with existing approaches struggling to generalize due to reliance on static visual cues and predefined instrument names. In this work, we introduce SurgRef, a novel motion-guided framework that grounds free-form language expressions in instrument motion, capturing how tools move and interact across time, rather than what they look like. This allows models to understand and segment instruments even under occlusion, ambiguity, or unfamiliar terminology. To train and evaluate SurgRef, we present Ref-IMotion, a diverse, multi-institutional video dataset with dense spatiotemporal masks and rich motion-centric expressions. SurgRef achieves state-of-the-art accuracy and generalization across surgical procedures, setting a new benchmark for robust, language-driven surgical video segmentation.

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AAAI Conference 2025 Conference Paper

Medical Multimodal Model Stealing Attacks via Adversarial Domain Alignment

Yaling Shen
Zhixiong Zhuang
Kun Yuan
Maria-Irina Nicolae
Nassir Navab
Nicolas Padoy
Mario Fritz

Medical multimodal large language models (MLLMs) are becoming an instrumental part of healthcare systems, assisting medical personnel with decision making and results analysis. Models for radiology report generation are able to interpret medical imagery, thus reducing the workload of radiologists. As medical data is scarce and protected by privacy regulations, medical MLLMs represent valuable intellectual property. However, these assets are potentially vulnerable to model stealing, where attackers aim to replicate their functionality via black-box access. So far, model stealing for the medical domain has focused on image classification; however, existing attacks are not effective against MLLMs. In this paper, we introduce Adversarial Domain Alignment (ADA-Steal), the first stealing attack against medical MLLMs. ADA-Steal relies on natural images, which are public and widely available, as opposed to their medical counterparts. We show that data augmentation with adversarial noise is sufficient to overcome the data distribution gap between natural images and the domain-specific distribution of the victim MLLM. Experiments on the IU X-RAY and MIMIC-CXR radiology datasets demonstrate that Adversarial Domain Alignment enables attackers to steal the medical MLLM without any access to medical data.

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NeurIPS Conference 2024 Conference Paper

Procedure-Aware Surgical Video-language Pretraining with Hierarchical Knowledge Augmentation

Kun Yuan
Vinkle Srivastav
Nassir Navab
Nicolas Padoy

Surgical video-language pretraining (VLP) faces unique challenges due to the knowledge domain gap and the scarcity of multi-modal data. This study aims to bridge the gap by addressing issues regarding textual information loss in surgical lecture videos and the spatial-temporal challenges of surgical VLP. To tackle these issues, we propose a hierarchical knowledge augmentation approach and a novel Procedure-Encoded Surgical Knowledge-Augmented Video-Language Pretraining (PeskaVLP) framework. The proposed knowledge augmentation approach uses large language models (LLM) to refine and enrich surgical concepts, thus providing comprehensive language supervision and reducing the risk of overfitting. The PeskaVLP framework combines language supervision with visual self-supervision, constructing hard negative samples and employing a Dynamic Time Warping (DTW) based loss function to effectively comprehend the cross-modal procedural alignment. Extensive experiments on multiple public surgical scene understanding and cross-modal retrieval datasets show that our proposed method significantly improves zero-shot transferring performance and offers a generalist visual repre- sentation for further advancements in surgical scene understanding. The source code will be available at https: //github. com/CAMMA-public/PeskaVLP.

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ICRA Conference 2019 Conference Paper

Self-Supervised Surgical Tool Segmentation using Kinematic Information

Cristian da Costa Rocha
Nicolas Padoy
Benoit Rosa

Surgical tool segmentation in endoscopic images is the first step towards pose estimation and (sub-)task automation in challenging minimally invasive surgical operations. While many approaches in the literature have shown great results using modern machine learning methods such as convolutional neural networks, the main bottleneck lies in the acquisition of a large number of manually-annotated images for efficient learning. This is especially true in surgical context, where patient-to-patient differences impede the overall generalizability. In order to cope with this lack of annotated data, we propose a self-supervised approach in a robot-assisted context. To our knowledge, the proposed approach is the first to make use of the kinematic model of the robot in order to generate training labels. The core contribution of the paper is to propose an optimization method to obtain good labels for training despite an unknown hand-eye calibration and an imprecise kinematic model. The labels can subsequently be used for fine-tuning a fully-convolutional neural network for pixel-wise classification. As a result, the tool can be segmented in the endoscopic images without needing a single manually-annotated image. Experimental results on phantom and in vivo datasets obtained using a flexible robotized endoscopy system are very promising.

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ICRA Conference 2017 Conference Paper

Pose optimization of a C-arm imaging device to reduce intraoperative radiation exposure of staff and patient during interventional procedures

Nicolas Loy Rodas
Julien Bert
Dimitris Visvikis
Michel de Mathelin
Nicolas Padoy

Minimally-invasive (MI) procedures are becoming more popular and frequent due to their benefits such as reduced patient trauma and hospitalization time. However, several common types of MI interventions are performed under X-ray guidance, which exposes both patients and staff to harmful ionizing radiation. Radiation exposure has therefore become a major concern for the medical community. Yet, few efforts to actively reduce it by exploiting the robotic capabilities of the devices present in the surgical suite have been performed. The propagation of radiation highly depends on the X-ray source positioning. Hence, we propose an approach to optimize the imaging device's pose in order to reduce the exposure to radiation of both patient and staff, while preserving the visibility of the targeted anatomical structure in the acquired image. Our method is based on the optimization of a cost function, which takes the current context and device parameters into account to compute the overall radiation exposure. It relies on GPU-accelerated Monte Carlo methods to simulate radiation propagation and performs the optimization in quasi real-time. When evaluated on a set of standard imaging configurations, our approach is able to recommend a device's pose in a few seconds, for which the delivered dose is reduced. Such an approach can contribute to lower the probability of appearance and severity of long-term negative effects due to radiation exposure and improve overall radiation safety.

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IROS Conference 2011 Conference Paper

3D thread tracking for robotic assistance in tele-surgery

Nicolas Padoy
Gregory D. Hager

Remote tele-manipulation tasks can be both long and exhausting. The operative workload can however be reduced through contextual systems, in which routine or dexterous actions are performed automatically. In this paper, we investigate this idea in tele-surgery by proposing automatic scissors, namely the possibility for a surgeon to invoke a third robotic arm to come and automatically cut the thread that he/she is holding. In particular, we address the problem of tracking deformable 3-dimensional (3D) curvilinear objects from stereo images. We propose an approach based on discrete Markov random field (MRF) optimization to track, in 3D, a thread modeled by a non-uniform rational B-spline (NURBS). We evaluate its accuracy off-line on synthetic and real data and illustrate its use for an automatic scissors command within an assistance system based on the da Vinci tele-surgical robot.

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ICRA Conference 2011 Conference Paper

Human-Machine Collaborative surgery using learned models

Nicolas Padoy
Gregory D. Hager

In the future of surgery, tele-operated robotic assistants will offer the possibility of performing certain commonly occurring tasks autonomously. Using a natural division of tasks into subtasks, we propose a novel surgical Human-Machine Collaborative (HMC) system in which portions of a surgical task are performed autonomously under complete surgeon's control, and other portions manually. Our system automatically identifies the completion of a manual subtask, seamlessly executes the next automated task, and then returns control back to the surgeon. Our approach is based on learning from demonstration. It uses Hidden Markov Models for the recognition of task completion and temporal curve averaging for learning the executed motions. We demonstrate our approach using a da Vinci tele-surgical robot. We show on two illustrative tasks where such human-machine collaboration is intuitive that automated control improves the usage of the master manipulator workspace. Because such a system does not limit the traditional use of the robot, but merely enhances its capabilities while leaving full control to the surgeon, it provides a safe and acceptable solution for surgical performance enhancement.

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