Détection de contours des organes pelviens dans des images médicales par modèles de B-spline

A ce jour, en routine clinique, grâce aux technologies avancées d'imagerie par résonance magnétique (IRM), le diagnostic des troubles du système pelvien chez la femme dépend de l'analyse d'images IRM par les médecins avec un risque de subjectivités. La simulation éléments finis est un outil prometteur pour l'aide à la compréhension qui, entre autre basée sur l'IRM, peut réduire la subjectivité des analyses. Pour cela, nous introduisons une méthode permettant d'identifier semi-automatiquement les organes pelviens observables sur des images IRM. Ce travail permet de mettre en place des mesures objectives et quantitatives, qui aide à la modélisation géométrique du système pelvien et à l'analyse des mobilités pour les études plus approfondies. Un modèle paramétré de B-spline est utilisé comme descriptif de géométries dédiées. Ce modèle initial est recalé sur l'organe présenté dans l'image réelle par corrélation d'images virtuelles. Nous avons validé la détection (de la vessie, du vagin et du rectum) sur un jeu de données de 19 patientes, présentant des mobilités physiologiques ou pathologiques

Calibration and External Force Sensing for Soft Robots using an RGB-D Camera

International audienceBenefiting from the deformability of soft robots, calibration and force sensing for soft robots are possible using an external vision-based system, instead of embedded mechatronic force sensors. In this paper, we first propose a calibration method to calibrate both the sensor-robot coordinate system and the actuator inputs. This task is addressed through a sequential optimization problem for both variables. We also introduce an external force sensing system based on a real-time Finite Element (FE) model with the assumption of static configurations, and which consists of two steps: force location detection and force intensity computation. The algorithm that estimates force location relies on the segmentation of the point cloud acquired by an RGB-D camera. Then, the force intensities can be computed by solving an inverse quasi-static problem based on matching the FE model with the point cloud of the soft robot. As for validation, the proposed strategies for calibration and force sensing have been tested using a parallel soft robot driven by four cables

Fracture in Augmented Reality

International audienceWe propose in this study an image-guided mesh cutting method to handle real-time augmentation of paper tearing. This method relieson the combination of visually-based fracture tracking algorithm and a physics-based model that is dynamically superimposed on the image

Vascular neurosurgery simulation with bimanual haptic feedback

International audienceVirtual surgical simulators face many computational challenges: they need to provide biophysical accuracy, realistic feed-backs and high-rate responses. Better biophysical accuracy and more realistic feed-backs (be they visual, haptic.. .) induce more computational footprint. State-of-the-art approaches use high-performance hardware or find an acceptable trade-off between performance and accuracy to deliver interactive yet pedagogically relevant simulators. In this paper, we propose an interactive vascular neurosurgery simulator that provides bi-manual interaction with haptic feedback. The simulator is an original combination of states-of-the-art techniques that allows visual realism, bio-physical realism, complex interactions with the anatomical structures and the instruments and haptic feedback. Training exercises are also proposed to learn and to perform the different steps of intracranial aneurysm surgery (IAS). We assess the performance of our simulator with quantitative performance benchmarks and qualitative assessments of junior and senior clinicians

Surgery Training, Planning and Guidance Using the SOFA Framework

International audienceIn recent years, an active development of novel technologies dealing with medical training, planning and guidance has become an increasingly important area of interest in both research and health-care manufacturing. A combination of advanced physical models, realistic human-computer interaction and growing computational power is bringing new solutions in order to help both medical students and experts to achieve a higher degree of accuracy and reliability in surgical interventions. In this paper, we present three different examples of medical physically-based simulations implemented in a common software platform called SOFA. Each example represents a different application: training for cardiac electrophysiology, pre-operative planning of cryosurgery and per-operative guidance for laparoscopy. The goal of this presentation is to evaluate the realism, accuracy and efficiency of the simulations, as well as to demonstrate the potential and flexibility of the SOFA platform

Motion Control of Cable-Driven Continuum Catheter Robot through Contacts

International audienceCatheter-based intervention plays an important role in minimally invasive surgery. For the closed-loop control of catheter robot through contacts, the loss of contact sensing along the entire catheter might result in task failure. To deal with this problem, we propose a decoupled motion control strategy which allows to control insertion and bending independently. We model the catheter robot and the contacts using the Finite Element Method. Then, we combine the simulated system and the real system for the closed-loop motion control. The control inputs are computed by solving a quadratic programming (QP) problem with a linear complementarity problem (LCP). A simplified method is proposed to solve this optimization problem by converting it into a standard QP problem. Using the proposed strategy, not only the control inputs but also the contact forces along the entire catheter can be computed without using force sensors. Finally, we validate the proposed methods using both simulation and experiments on a cable-driven continuum catheter robot for the real-time motion control through contacts

Impact of Soft Tissue Heterogeneity on Augmented Reality for Liver Surgery

International audienceThis paper presents a method for real-time augmented reality of internal liver structures during minimally invasive hepatic surgery. Vessels and tumors computed from pre-operative CT scans can be overlaid onto the laparoscopic view for surgery guidance. Compared to current methods, our method is able to locate the in-depth positions of the tumors based on partial three-dimensional liver tissue motion using a real-time biomechanical model. This model permits to properly handle the motion of internal structures even in the case of anisotropic or heterogeneous tissues, as it is the case for the liver and many anatomical structures. Experimentations conducted on phantom liver permits to measure the accuracy of the augmentation while real-time augmentation on in vivo human liver during real surgery shows the benefits of such an approach for minimally invasive surgery

Software toolkit for modeling, simulation and control of soft robots

International audienceThe technological differences between traditional robotics and soft robotics have an impact on all of the modeling tools generally in use, including direct kinematics and inverse models, Jacobians, and dynamics. Due to the lack of precise modeling and control methods for soft robots, the promising concepts of using such design for complex applications (medicine, assistance, domestic robotics...) cannot be practically implemented. This paper presents a first unified software framework dedicated to modeling, simulation and control of soft robots. The framework relies on continuum mechanics for modeling the robotic parts and boundary conditions like actuators or contacts using a unified representation based on Lagrange multipliers. It enables the digital robot to be simulated in its environment using a direct model. The model can also be inverted online using an optimization-based method which allows to control the physical robots in the task space. To demonstrate the effectiveness of the approach, we present various soft robots scenarios including ones where the robot is interacting with its environment. The software has been built on top of SOFA, an open-source framework for deformable online simulation and is available at https://project.inria.fr/softrobot

Fracture in Augmented Reality

International audienceWe propose in this study an image-guided mesh cutting method to handle real-time augmentation of paper tearing. This method relieson the combination of visually-based fracture tracking algorithm and a physics-based model that is dynamically superimposed on the image

Monocular 3D Reconstruction and Augmentation of Elastic Surfaces with Self-occlusion Handling

International audienceThis paper focuses on the 3D shape recovery and augmented reality on elastic objects with self-occlusions handling, using only single view images. Shape recovery from a monocular video sequence is an underconstrained problem and many approaches have been proposed to enforce constraints and resolve the ambiguities. State-of-the art solutions enforce smoothness or geometric constraints, consider specific deformation properties such as inextensibility or resort to shading constraints. However, few of them can handle properly large elastic deformations. We propose in this paper a real-time method that uses a mechanical model and able to handle highly elastic objects. The problem is formulated as an energy minimization problem accounting for a non-linear elastic model constrained by external image points acquired from a monocular camera. This method prevents us from formulating restrictive assumptions and specific constraint terms in the minimization. In addition, we propose to handle self-occluded regions thanks to the ability of mechanical models to provide appropriate predictions of the shape. Our method is compared to existing techniques with experiments conducted on computer-generated and real data that show the effectiveness of recovering and augmenting 3D elastic objects. Additionally, experiments in the context of minimally invasive liver surgery are also provided and results on deformations with the presence of self-occlusions are exposed