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This paper presents a new structured light approach dedicated to 3D mapping of underwater galleries in karst aquifers. This kind of method is based on the projection of a light pattern onto the scene captured by a camera. Our originality comes from the projected pattern used, since unlike literature methods, our light projector is a simple conical diving light. With a light cone, the recovered pattern in the image is a closed 2D curve we extract with a light contour detection method we have developed. A specific calibration method has also been created to estimate the cone geometry with respect to the camera. Therefore, we get a calibrated projector-camera pair, we can use to find matches between projected and recovered patterns. Our last contribution is the recovery of 3D data by triangulation using the camera cone relationship and the extracted closed 2D curve. The experimental results that will be presented in this article show the feasibility of the method.

International audience; Objective: The noninvasive measurement of venous wall deformation induced by changes in transmural pressure could allow for the assessment of viscoelasticity and differentiating normal from diseased veins.Methods: In 57 patients with limbs in the C1s (telangiectasia or reticular veins and symptoms), C3 (edema), or C5 (healed venous ulcer) CEAP (clinical, etiologic, anatomic, pathophysiologic) category of chronic venous disease and 54 matched healthy controls, we measured the changes in the cross-sectional area of the small saphenous vein and a deep calf vein in the supine and standing positions and under compression with an ultrasound probe using ultrasonography.Results: The small saphenous vein, but not the deep calf vein, cross-sectional area was smaller in the limbs of the controls than in the limbs with C3 or C5 disease but was not different from that in C1s limbs. When changing from the supine to the standing position, a greater force was required to collapse the leg veins. Their cross-sectional area increased in most subjects but decreased in 31.5% of them as for the small saphenous veins and 40.5% for the deep calf vein. The small saphenous vein area vs compression force function followed a hysteresis loop, demonstrating viscoelastic features. Its area, which represents the viscosity component, was greater (P < .001) in the pooled C3 and C5 limbs (median, 2.40 N⋅mm2; lower quartile [Q1] to upper quartile [Q3], 1.65-3.88 N⋅mm2) than in the controls (median, 1.24 N⋅mm2; Q1-Q3, 0.64-2.14 N⋅mm2) and C1s limbs (median, 1.15 N⋅mm2; Q1-Q3, 0.71-2.97 N⋅mm2). The area increased (P < .0001) in the standing position in all groups.Conclusions: Postural changes in the cross-sectional area of the leg veins were highly diverse among patients with chronic venous disease and among healthy subjects and appear unsuitable for pathophysiologic characterization. In contrast, small saphenous vein viscoelasticity increased consistently in the standing position and the viscosity was greater in limbs with C3 and C5 CEAP disease than in controls.

OBJECTIVE To determine the effects of graduated and progressive elastic compression stockings (ECS) on postural diameter changes and viscoelasticity of leg veins in healthy controls and in limbs with chronic venous disease (CVD). METHODS In 57 patients whose legs presented with C1s, C3, or C5 CEAP classes of chronic venous disease and were treated primarily with compression, and 54 healthy controls matched for age and body mass index, we recorded interface pressures (IFP) at 9 reference leg levels. Cross-sectional areas of the small saphenous vein (SSV) and a deep calf vein (DCV) were measured with B-mode ultrasound with patients supine and standing, recording the force (PF) applied on the ultrasound probe to collapse each vein with progressive ECS, and with and without graduated 15 to 20 mm Hg and 20 to 36 mm Hg elastic stockings. We chose these veins because they were free of detectable lesion and could be investigated at the same level (mid-height of the calf), and their compression by the ultrasound probe was not hampered by bone structures. RESULTS IFP decreased from ankle to knee with graduated 15 to 20 and 20 to 36 mm Hg, but increased with progressive ECS, and were 8.4 to 13.8 mm Hg lower for C1s than for control or C3 and C5 limbs. Without ECS, the SSV median [lower-upper quartile] cross-sectional area was 4.9 mm2 [3.6-7.1 mm2] and 7.1 mm2 [3.0-9.9 mm2] in C3 and C5 limbs versus 2.9 mm2 [1.8-5.2 mm2] and 3.8 mm2 [2.1-5.4 mm2] in controls (P < .01), respectively, while supine and standing. It remained greater in C3 and C5 than in C1s and control limbs wearing any ESC. Wearing compression, especially with progressive ECS, decreased the SSV and DCV cross-sectional area only with patients supine, thus decreasing postural changes, which remained highly diverse between individuals. The SSV cross-sectional area versus PF function traced a hysteresis loop of which the area, related to viscosity, was greater in C3 and C5 limbs than controls, even with graduated 15 to 20 or 20 to 36 mm Hg ECS. Progressive ECS decreased vein viscosity in the supine position, whereas 20 to 36 mm Hg and progressive ECS increased distensibility in the standing position. CONCLUSIONS ECS decrease the cross-sectional area of SSV and DCV with patients supine, but not upright. C1s limbs show distinctive features, especially regarding IFP. Graduated 20 to 36 mm Hg and progressive stockings lower viscosity and increase distensibility of the SSV.

The aim of this study was to analyze the temporal relationships between pressure, flow, and Korotkoff sounds, providing clues for their comprehensive interpretation.When measuring blood pressure in a group of 23 volunteers, we used duplex Doppler ultrasonography to assess, under the arm-cuff, the brachial artery flow, diameter changes, and local pulse wave velocity (PWV), while recording Korotkoff sounds 10 cm downstream together with cuff pressure and ECG.The systolic (SBP) and diastolic (DBP) blood pressures were 118.8±17.7 and 65.4±10.4 mmHg, respectively (n=23). The brachial artery lumen started opening when cuff pressure decreased below the SBP and opened for an increasing length of time until cuff pressure reached the DBP, and then remained open but pulsatile. A high-energy low-frequency Doppler signal, starting a few milliseconds before flow, appeared and disappeared together with Korotkoff sounds at the SBP and DBP, respectively. Its median duration was 42.7 versus 41.1 ms for Korotkoff sounds (P=0.54; n=17). There was a 2.20±1.54 ms/mmHg decrement in the time delay between the ECG R-wave and the Korotkoff sounds during cuff deflation (n=18). The PWV was 10±4.48 m/s at null cuff pressure and showed a 0.62% decrement per mmHg when cuff pressure increased (n=13).Korotkoff sounds are associated with a high-energy low-frequency Doppler signal of identical duration, typically resulting from wall vibrations, followed by flow turbulence. Local arterial PWV decreases when cuff pressure increases. Exploiting these changes may help improve SBP assessment, which remains a challenge for oscillometric techniques.

International audience; This work presents the 3D reconstruction of the archeology objects in underwater environment. The videos and images are obtained from a calibrated camera system. The features of interest between image pairs are selected by the FAST detector and FLANN descriptor. Subsequently, the RANSAC method is applied to reject outlier points. The putative inliers are matched by triangulation to produce sparse point clouds in 3D space, using a pinhole camera model and Euclidean distance estimation. The 3D model textrue is achieved through a commond 3D Delaunay triangulation procedure. Moreover, evaluation of the quality of the underwater 3D reconstruction model to find its accuracy is done by measurement, comparing it with a 3D industrial scan model as well as a real object.

International audience; The objective of this paper is to develop 3D underwater reconstruction of archeology object, which is based on a mono-camera. The underwater images are obtained from a calibrated camera system. We first solve the problem of image processing by applying the well-known filter, therefore to improve quality of underwater images. The features of interest between image pairs are selected by well-known methods: a FAST detector and FLANN descriptor. Subsequently, the RANSAC method is applied to reject outlier points. The putative inliers are matched by triangulation to produce sparse point clouds in 3D space, using a pinhole camera model and Euclidean distance estimation.

International audience; Ultrasound examination is the first line procedure for the diagnosis and follow-up of cardiovascular diseases. Instrumenting an ultrasound probe with a force sensor may improve the non-invasive measurement of arterial biomechanical parameters (diameter, pulsatility, intima-media thickness and flow-dependent dilation) by measuring and controlling the force exerted by the sonographer. We present here the results obtained with this approach coupled with image processing for the measurement of arterial diameter changes during the cardiac cycle and dynamic tests. The analysis of artery force feedback provided non-invasively an estimation of blood pressure waveform.

International audience; BackgroundMeasurement of limb volume is helpful for the evaluation and follow-up of edema, especially in patients with chronic venous insufficiency (CVI) or lymphedema. Water displacement (WD) is the reference method for limb volumetry but is not really suitable for clinical routine. Indirect volumetry based on circumference measurements as well as the more expansive but automatic optoelectronic techniques do not allow detailed measurement at the extremity of the limb. Methods We used a self-positioning laser scanner with dynamic referencing for acquisition and real-time three-dimensional (3D) reconstruction of the lower limb volume in 30 patients with CVI, 30 patients with lymphedema, and 30 healthy controls. Two independent observers performed either one or two laser scans, whose results were tested for intra- and interobserver reproducibility and compared with WD volumetry by Lin's concordance correlation coefficient and Bland and Altman graphic analysis. Results Automatic volume calculation from 3D laser scanning data failed in one patient with major lymphedema. Lin's concordance correlation coefficient was 0.99 and 0.98, respectively, for intraobserver no. 1 and no. 2, 0.98 for interobserver reproducibility, and 0.98 and 0.96, respectively, for observer no. 1 and observer no. 2 vs WD comparison. The 3D laser scanning yielded 1.99% precision. Accuracy was 3.12% for observer no. 1 and 2.71% for observer no. 2, laser scanning values being 90 mL higher than WD, which could be attributed to the different posture during measurement. Conclusions Three-dimensional laser scanning is accurate and reproducible, and appears suitable for the evaluation of limb volume in patients with CVI or lymphedema.

We present a new approach for the evaluation of the biomechanical properties of lower limb veins based on the simultaneous measurements of the vein cross-sectional area with B-mode ultrasound imaging and of the force exerted on the skin by the ultrasound probe. Ongoing clinical trials allowed us to identify a behavioral model of lower limb veins without and with compression stockings.

We have shown that it's possible to realize a stereoscopic sensor with poor cameras. We developed image processing that is robust and allows us to quickly obtain results for the matching algorithm. We computed an important number of features on each segment, and with these features, we built 16-component vector used in the classification step. After an exhaustive study, we decided to combine two methods, Bayesian and neural, to construct an efficient classifier. The tests for indoor images had better than 90% good matching. With segment couples, it is possible to compute the 3D coordinates of the objects. Therefore, the mobile robot is able to localize and move about in the environment.

A laser range finder mounted on a site and azimuth turret is used as a 3D range camera. It forms, associated with a video camera, an original stereovision system. The internal structure of both images are the same but the resolution of 3D image stays low. By ignoring the acquiring speed of measures, spatial resolution is limited by the accuracy of deviation device and the laser footprint. The fact that the impact of the beam is not a point introduces spatial integration.To correct the average at depth discontinuities due to the beam footprint, a neural-network-based solution is reported.The use of such a multisensor system requires its calibration. As camera calibration is a well-known problem, the paper focuses on models and calibration methods of the range finder. Experimental results illustrate the quality of the calibration step in terms of accuracy and stability.The footprint correction is evaluated for both 1D and 2D range finder scannings.

International audience; The underwater cartography has made great progress in the last decade. In this paper, we discuss of the 3D underwater cartography problem and propose a multimodal fusion approach. The work presented in this paper is about the analyze and 3D reconstruction of archeological objects. Using an uncalibrated single camera, we propose to describe a method to firstly, calibrate this camera integrating variation of the water optical refractive index to the distortion model. And secondly, robust and stable features have been extracted. A comparison of two methods of detecting and matching points is presented. Finally, we estimate the movement between different images and compare two methods.

International audience; This article presents a new method for estimating the pose of para-catadioptric vision systems. It is based on the estimation of vanishing points associated with vertical edges of the environment. However, unlike classical approaches no feature (line, circle) extraction and/or identification is needed. A sampled domain of possible vanishing points is tested and histograms are build to characterize the soundness of these points. A specificity index allows to find the more relevant histogram and the pose of the sensor. This method has been tested on simulated and real images giving very promising results (maximum angular error of 0.18 degree).

National audience; Dans cet article, nous nous intéressons au suivi d'un organe en mouvement, un coeur battant en imagerie endoscopique et à l'évaluation de ses mouvements dans l'image et dans l'espace. La tâche est complexe, car le coeur est un objet déformable et la nature de sa surface (réflexivité, forte homogénéité de certaines zones) pose plusieurs problèmes en terme de suivi. De plus l'aspect médical suppose de trouver une méthode à la fois ro-buste et précise. Nous proposons de faire un compromis entre les méthodes de pattern matching (précises) et le suivi de charactéristiques liées à la textures (plus ro-buste) afin d'obtenir des performances intéressantes. Mots clefs Suivi visuel, coeur battant, imagerie médicale, robo-tique médicale, texture, ESM.

National audience; Le suivi des maladies cardiovasculaires est principalement effectué en imagerie échographique. L'instrumentation d'une sonde doit permettre de coupler la mesure des paramètres image (diamètre, épaisseur de la paroi...) avec une information sur la pression artérielle tout en contrôlant l'effort exercé par le praticien par une mesure non invasive. Nous présentons les premiers résultats permettant de réaliser cette mesure conjointe grâce a un capteur d'effort placé sur une sonde et à des traitements fiables pour le calcul du diamètre de l'artère.

International audience; In robot-assisted beating heart surgery, motion of the heart surface might be virtually stabilized to let the surgeon work as in on-pump cardiac surgery. Virtual stabilization means to compensate physically the relative motion between the instrument tool tip and the region of interest on the heart surface, and to offer surgeon a stable visual display of the scene. To this end, motion of the heart must be estimated. This article focusses on motion estimation of the heart surface. Two approaches are considered in the paper. The first one is based on landmark tracking allowing 3D pose estimation. The second is based on texture tracking. Classical computer vision methods, as well as a new texture-based tracking scheme has been applied to track the heart motion, and, when possible, reconstruct 3D distance to the heart surface. Experimental results obtained on in vivo images show the estimated motion of heart surface points.

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International audience; In robotic assisted beating heart surgery, motion of the heart surface might be virtually stabilized to let the surgeon work as in on-pump cardiac surgery. Virtual stabilization means to compensate physically the relative motion between instrument tool tip and point of interest on the heart surface, and to offer surgeon a stable visual display of the scene. In this way, motion of the heart must be estimated. This article focus on motion estimation of heart surface. Classical computer vision method has been applied to reconstruct 3D pose of interest point. Experimental results obtained on in vivo images show the estimated motion of heart surface points.

Our problem is a diagnostic task. Due to environment degraded conditions, direct measurements are not possible. Due to the rapidity of the machine, human intervention is not possible in case of position fault. So, an oriented vision solution is proposed. The problem must be solved for high velocity industrial tooling machines. Degraded conditions: vibrations, water and chip of metal projections, dazzling..., are present all the time. Image analysis in constraint environment depends on constraint importance. Before tooling, the vision system has to answer: “is it the right piece at the right place?” Complementary methods presented in this paper are proposed in an adaptive way to solve this diagnostic problem. This detection is made by comparing an acquired camera image of the piece to be tooled with an image of reference. Some image processing methods are performed and combined in order to extract 2D features. Some of these 2D features are evaluated and used as parameters in a diagnostic process. After a data analysis, image parameters are reduced. First, we present an overview of image processing methods generally used to solve that kind of problem and their limitations in our particular degraded case. In order to obtain automatic and robust classification, two methods are implemented. The first one is based on Bayes technique that provides a good classification in case of fault presence. The second method is based on neural networks and provides good results in case of images without faults. These two methods give a global rate of good classification greater than 90%, for 720 images acquired from an industrial site. Keywords: diagnostic task, 2D vision, video camera, image matching, bayes classifier, neural classifier Global Journal of Pure and Applied Sciences Vol. 12(2) 2006: 229-238

The device consists of a camera which gives the HO an indirect view of a scene (real world); proprioceptive and exteroceptive sensors allowing the recreating of the 3D geometric database of an environment (virtual world). The virtual world is projected onto a video display terminal (VDT). Computer-generated and video images are superimposed. The man-machine interface functions deal mainly with on line building of graphic aids to improve perception, updating the geometric database of the robotic site, and video control of the robot. The superimposition of the real and virtual worlds is carried out through a calibration of the multisensor system. First, the sensing system and several methods used for modeling an environment\'s geometric database in telerobotics have been presented. The operator models unknown objects (of cylindrical or polyhedral pattern) using a video camera(VC) image and a range finder(RF). When the quality of images is poor, the range finder, which is mounted on a site and azimuth rotation turret, brings an indispensable complement by measures of depth. The improvement offered by the cooperation VC/RF has been shown for small depths (below 1.6m). In some particular cases we propose to achieve the fusion of multisensor redundant data, in order to reduce the uncertainty. Then the updating of environment's 3D geometric database in telerobotics by single camera view is presented. It concerns the pose determination of known objects using 2D clues obtained through video images. A two step algorithm is implemented and assessed. The first step is available in case of object large motion, it is a geometric algorithm, which doesn\'t use redundant data; .it provides a first estimate of the pose. The second step is available in case of object small motion. A linear approach is carried out to determine the pose. It allows the use of redundant data. so it improves the accuracy achieved after the first step. KEY WORDS: Teleoperation, Telerobotics, Range finder; Video camera; Sensor modeling; 3D database updating, Image matching. Global Journal of Pure and Applied Sciences Vol.11(1) 2005:153-163

In order to permit the localization and the navigation of a mobile robot within an interior environment, we have built a stereoscopic sensor and implemented all the algorithms which allow to obtain 3D coordinates of real objects from data images. Sensor uses two mini cameras with vertical disposition. Processing on the images leads us to have segments on the two images. To match segments, we have to answer at the question: “Is there two segments, in a pair from top and bottom images segments, are two views of the same part of the real world of the robot ?”. For choosing the best matching algorithm, we compare three approaches: epipolar , Bayesian and neuronal techniques. In the epipolar method, we use only geometrical features. Two images of a single scene/object are related by the epipolar geometry, which can be describe by a 3x3 singular matrix called the fundamental matrix. It captures all geometric information contained in two images, and its determination is very important in many applications such as scene modeling and navigation of a mobile robot. With the two others, we associate to each segment, a set of 16 parameters which includes geometrical, gray level, textural and neighborhood features. For the comparison of these approaches, we have built a database of over 2500 segments. Results about this work are presented in our paper. Results with the two techniques from the data classification, are very good. In order to increase the quality of the segments matching, it is possible to find a combination rule for these two approaches. But, even if for the epipolar method 22% segments are not recognized, we think it is interesting to introduce it with the aim to obtain better results in some difficult configurations, by example when gray levels and textures are not very different in the scene, and also in order to initialize the classification algorithm. KEY WORDS: . Global Jnl Pure & Applied Sciences Vol.10(2) 2004: 335-341

According to the problem to be dealt with, the use of data acquisition system requires the knowledge of several models. In the case of the laser range-finder mounted on a site and azimuth turret, the geometrical model defines the co-ordinate transformation between measurement and reference frames. The paper shows the interest of a global calibration in comparison with a more classical approach which divides the problem into an internal model and external one. During the acquisition process another model called 'physical model' may be useful. It takes into account the fact the laser beam impact is not at a point and introduces a spatial integration. The so-called footprint effect limits the lateral resolution of the range finder at depth discontinuities. In order to correct that effect, an inverse physical model, based on neural networks, is proposed. The improvement of the footprint correction is then evaluated for a 2D and 3D scanning.

International audience; Among the issues raised by Computer Vision, the tracking of one or several regions of interest is a major consideration. Achieving accuracy and robustness is critical in Visual Servoing and more generally in vision-based applications because of the sensibility of the algorithms. To address those issues in the specific case of MIS heart surgery, we developed a texture-based approach that provide good results on experimental beating heart images. Our approach consists in integrating textural characterization of the region of interest to reinforce the tracking procedure based on classical approaches such as correlation. We show that an appropriate combination of image descriptors can improve the efficiency of the tracking, especially on low-contrasted medical images.

Performing motion tracking in real-time is an old and recurrent problem in Computer Vision. It has been addressed through a large set of approaches [17], [9], [1], but achieving a high level of robustness is still a challenge, especially with low definition input. In the considered application, tracking the heart motion in endoscopic beating heart sequences, the sensitivity of existing algorithms to visual artifacts and variations in illumination is an issue that calls for improvements. In the prospect of developing a motion compensation architecture for robotically assisted beating heart surgery, we address the problem of visual information retrieval by proposing a new Composite Tracking Algorithm using both template matching and texture analysis. As we will show in this paper, the use of texture characterization of the heart surface improves the overall precision and robustness, in comparison with other prior approaches.

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