Shearlet-based vs. Photometric-based Visual Servoing for Robot-assisted Medical Applications

International audience— This paper deals with the development of a vision-based controller for robot-assisted medical applications. It concerns the use of shearlet coefficients in case of ultrasounds (US) images as visual signal inputs and the design of the associated interaction matrix. The proposed controller was validated in both simulation and on an experimental test bench which consists of a robotic arm holding an US probe in contact with a realistic abdominal phantom. Also, the proposed control scheme was compared to the photometry-based visual servoing approach in order to evaluate its efficiency in different conditions of use (nominal and unfavorable conditions)

Mixed-mode oscillations in a multiple time scale phantom bursting system

In this work we study mixed mode oscillations in a model of secretion of GnRH (Gonadotropin Releasing Hormone). The model is a phantom burster consisting of two feedforward coupled FitzHugh-Nagumo systems, with three time scales. The forcing system (Regulator) evolves on the slowest scale and acts by moving the slow nullcline of the forced system (Secretor). There are three modes of dynamics: pulsatility (transient relaxation oscillation), surge (quasi steady state) and small oscillations related to the passage of the slow nullcline through a fold point of the fast nullcline. We derive a variety of reductions, taking advantage of the mentioned features of the system. We obtain two results; one on the local dynamics near the fold in the parameter regime corresponding to the presence of small oscillations and the other on the global dynamics, more specifically on the existence of an attracting limit cycle. Our local result is a rigorous characterization of small canards and sectors of rotation in the case of folded node with an additional time scale, a feature allowing for a clear geometric argument. The global result gives the existence of an attracting unique limit cycle, which, in some parameter regimes, remains attracting and unique even during passages through a canard explosion.Comment: 38 pages, 16 figure

LLM-based Interaction for Content Generation: A Case Study on the Perception of Employees in an IT department

In the past years, AI has seen many advances in the field of NLP. This has led to the emergence of LLMs, such as the now famous GPT-3.5, which revolutionise the way humans can access or generate content. Current studies on LLM-based generative tools are mainly interested in the performance of such tools in generating relevant content (code, text or image). However, ethical concerns related to the design and use of generative tools seem to be growing, impacting the public acceptability for specific tasks. This paper presents a questionnaire survey to identify the intention to use generative tools by employees of an IT company in the context of their work. This survey is based on empirical models measuring intention to use (TAM by Davis, 1989, and UTAUT2 by Venkatesh and al., 2008). Our results indicate a rather average acceptability of generative tools, although the more useful the tool is perceived to be, the higher the intention to use seems to be. Furthermore, our analyses suggest that the frequency of use of generative tools is likely to be a key factor in understanding how employees perceive these tools in the context of their work. Following on from this work, we plan to investigate the nature of the requests that may be made to these tools by specific audiences.Comment: 14 pages (bibliography inclued), 6 figures, preprint submitted to Work-In-Progress session of ACM IMX'23 Interactive Media Experienc

A Network Model of the Periodic Synchronization Process in the Dynamics of Calcium Concentration in GnRH Neurons

International audienceMathematical neuroendocrinology is a branch of mathematical neurosciences that is specifically interested in endocrine neurons, which have the uncommon ability of secreting neurohormones into the blood. One of the most striking features of neuroendocrine networks is their ability to exhibit very slow rhythms of neurosecretion, on the order of one or several hours. A prototypical instance is that of the pulsatile secretion pattern of GnRH (gonadotropin releasing hormone), the master hormone controlling the reproductive function, whose origin remains a puzzle issue since its discovery in the seventies. In this paper, we investigate the question of GnRH neuron synchronization on a mesoscopic scale, and study how synchronized events in calcium dynamics can arise from the average electric activity of individual neurons. We use as reference seminal experiments performed on embryonic GnRH neurons from rhesus monkeys, where calcium imaging series were recorded simultaneously in tens of neurons, and which have clearly shown the occurrence of synchronized calcium peaks associated with GnRH pulses, superposed on asynchronous, yet oscillatory individual background dynamics. We design a network model by coupling 3D individual dynamics of FitzHugh-Nagumo type. Using phase-plane analysis, we constrain the model behavior so that it meets qualitative and quantitative specifications derived from the experiments, including the precise control of the frequency of the synchronization episodes. In particular, we show how the time scales of the model can be tuned to fit the individual and synchronized time scales of the experiments. Finally, we illustrate the ability of the model to reproduce additional experimental observations, such as partial recruitment of cells within the synchronization process or the occurrence of doublets of synchronization

Commande d'un robot de télé-échographie par asservissement visuel

Les robots légers utilisés pour la télé-échographie robotisée permettent, à l'expert médical, d'orienter à distance une sonde ultrasonore 2D. L'analyse en temps réel de l'image ultrasonore du patient, reçue via un lien de communication, permet à l'expert de définir un diagnostic. Les validations cliniques du concept de télé-échographie robotisée montrent qu'il est ainsi possible de pallier le manque d'experts en ultrasonographie sur des sites médicalement isolés. Le robot porte-sonde est positionné et maintenu sur le corps du patient par un assistant à partir des informations communiquées par le spécialiste via visioconférence. Cependant, la faible masse du robot, le fait qu'il soit maintenu par un assistant sur le corps du patient et les mouvements physiologiques du patient provoquent des perturbations dans la position de la sonde et engendrent ainsi des pertes des sections d'intérêt des organes étudiés. Les travaux de cette thèse ont consisté à développer une approche par asservissement visuel basé sur les moments d'image ultrasonore 2D. Le calcul des moments 2D étant basé sur les points du contour de la section d'intérêt, un algorithme de traitement d'images efficace est nécessaire pour détecter et suivre le contour d'intérêt en mouvement. Pour cela, une méthode de contour actif paramétrique basée sur les descripteurs de Fourier est présentée. Les lois de commandes correspondant à trois tâches autonomes autorisant la recherche et le maintien de visibilité d'un organe lors de l'acte médical télé-opéré sont implémentées et validées sur la plateforme robotique du projet ANR Prosit.The light weight robots used for robotized tele-echography allow the medical expert to remotely operate a 2D-ultrasound probe. The real-time analysis of the patient's ultrasound images, received via a standard communication link, provides the expert with relevant information to define a diagnosis. The clinical validations of the robotized tele-echography concept show that it is possible to overcome the lack of sonographers in medically isolated sites. The robot probe-holder is usually positioned and held on the patient's body by a paramedical staff based on information provided by the specialist via videoconferencing. However, the small mass of the robot, the fact that it is held by an assistant on the patient's body and the patient's physiological movements cause disturbances in the position of the probe ; this thus can generate a loss of the region of interest of the organ being under investigation during the teleoperated medical act. This thesis work focuses on the development of a visual servoing approach based on 2D ultrasound image moments. 2D moments calculation is based on the contour points of the image section of interest, therefore an image-processing algorithm is needed to effectively detect and follow the contour of interest in motion. For this reason, a parametric active contour method based on Fourier descriptors is presented. The control laws, corresponding to three independent autonomous tasks to search and maintain the visibility of an organ within a given ultrasound plane during the tele-operated medical act are implemented and validated on robotic platform project ANR Prosit.RENNES1-Bibl. électronique (352382106) / SudocSudocFranceF

Confidence-Driven Control of an Ultrasound Probe: Target-Specific Acoustic Window Optimization

International audienceWe propose a control framework to optimize the quality of robotic ultrasound imaging while tracking an anatomical target. We use a multitask approach to control the in-plane motion of a convex probe mounted on the end-effector of a robotic arm, based not only on the position of the target in the image, but also on features extracted from an ultrasound confidence map. The resulting control law therefore guarantees a good image quality, while keeping the target aligned with the central ultrasound scan-line. Potential applications of the proposed approach are, for example, teleoperated ultrasound examination, motion compensation for ultrasound-guided interventions , or automatic ultrasound acquisition. We demonstrate our approach with experiments on an ultrasound examination training phantom in motion

Vision-based assistance for wheelchair navigation along corridors

International audienceIn case of motor impairments, steering a wheelchair can become a hazardous task. Typically, along corridors, joystick jerks induced by uncontrolled motions are source of wall collisions. This paper describes a vision based assistance solution for safe indoor semi-autonomous navigation purposes. To this aim, the control process is based on a visual servoing process designed for wall avoidance purposes. As the patient manually drives the wheelchair, a virtual guide is defined to progressively activate an automatic trajectory cor- rection. The proposed solution does not require any knowledge of the environment. Experiments have been conducted over corridors that present different configurations and illumination conditions. Results demonstrate the ability of the system to smoothly and adaptively assist people during their motions

Analytical insights on theta-gamma coupled neural oscillators

International audienceIn this paper we study the dynamics of a quadratic integrate-and-fire neuron, spiking in the gamma (30-100 Hz) range, coupled to a delta/theta frequency (1-8 Hz) neural oscillator. Using analytical and semi-analytical methods we were able to derive characteristic spiking times for the system in two distinct regimes (depending on parameter values): one regime where the gamma neuron is intrinsically oscillating in the absence of theta input, and a second one in which gamma spiking is directly gated by theta input, i.e. windows of gamma activity alternate with silence periods depending on the underlying theta phase. In the former case we transform the equations such that the system becomes analogous to the Mathieu differential equation. By solving this equation we can compute numerically the time to the first gamma spike and then use singular perturbation theory to find successive spike times. On the other hand in the excitable condition we make direct use of singular perturbation theory to obtain an approximation of the time to first gamma spike, and then extend the result to calculate ensuing gamma spikes in a recursive fashion. We thereby give explicit formulas for the onset and offset of gamma spike burst during a theta cycle, and provide an estimation of the total number of spikes per theta cycle both for excitable and oscillator regimes

Indirect Positioning of a 3D Point on a Soft Object Using RGB-D Visual Servoing and a Mass-Spring Model

This work was supported by the GentleMAN (299757) and the BIFROST (313870) projects funded by The Research Council of Norway.International audienceIn this paper, we present a complete pipeline for positioning a feature point of a soft object to a desired 3D position, by acting on a different manipulation point using a robotic manipulator. For that purpose, the analytic relation between the feature point displacement and the robot motion is derived using a coarse mass-spring model (MSM), while taking into consideration the propagation delay introduced by a MSM. From this modeling step, a novel closed-loop controller is designed for performing the positioning task. To get rid of the model approximations, the object is tracked in realtime using a RGB-D sensor, thus allowing to correct on-line any drift between the object and its model. Our model-based and vision-based controller is validated in real experiments for two different soft objects and the results show promising performance in terms of accuracy, efficiency and robustness