M. de Mathelin

Needle insertions modeling: Identifiability and limitations

Abstract Soft tissues modeling is a very present preoccupation in different scientific fields, from computer simulation to biomechanics or medical robotics. In this article, we consider the interaction of a needle with living tissues, which is a particularly complex modeling problem since it is characterized by inhomogeneity and nonlinearity properties. We propose a robust method to online estimate forces involved in typical percutaneous interventions. The ability to obtain physically consistent models during in vivo insertions is also discussed.

Segmentation and guidance of multiple rigid objects for intra-operative endoscopic vision

This paper presents an endoscopic vision framework for model-based 3D guidance of surgical instruments used in robotized laparoscopic surgery. In order to develop such a system, a variety of challenging segmentation, tracking and reconstruction problems must be solved. With this minimally invasive surgical technique, every single instrument has to pass through an insertion point in the abdominal wall and is mounted on the end-effector of a surgical robot which can be controlled by automatic visual feedback. The motion of any laparoscopic instrument is then constrained and the goal of the automated task is to safety bring instruments at desired locations while avoiding undesirable contact with internal organs. For this eye-to-hands configuration with a stationary camera, most control strategies require the knowledge of the out-of-field of view insertion points location and we demonstrate it can be achieved in vivo thanks to a sequence of (instrument) motions without markers and without the need of an external measurement device. In so doing, we firstly present a real-time region-based color segmentation which integrates this motion constraint to initiate the search for region seeds. Secondly, a novel pose algorithm for the wide class of cylindrical-shaped instruments is developed which can handle partial occlusions as it is often the case in the abdominal cavity. The foreseen application is a good training ground to evaluate the robustness of segmentation algorithms and positioning techniques since main difficulties came from the scene understanding and its dynamical variations. Experiments in the lab and in real surgical conditions have been conducted. The experimental validation is demonstrated through the 3D positioning of instruments axes (4 DOFs) which must lead to motionless insertion points disturbed by the breathing motion.

Physiological motion rejection in flexible endoscopy using visual servoing

Flexible endoscopes are used in many surgical procedures and diagnostic exams, like in gastroscopy or coloscopy. They have also been used recently for new surgical procedures using natural orifices called NOTES. While these procedures are very promising for the patients, they are quite awkward for the surgeons. The flexible endoscope allows the access to operating areas which are not easily reachable, with small or no incisions; but the manipulation of the system is complex. In order to help the practicians during NOTES or classical interventions with flexible endoscopes, we propose to motorize the system so as to partially robotize the movements. This paper presents the problems in the use of the flexible endoscope and explains how the system can be used to stabilize the endoscope on an area of interest despite physiological motions and therefore to improve the manipulation of the system.

Nonlinear modeling of low cost force sensors

In this paper, nonlinear modeling of low cost force sensors is considered for force control applications in robotic or biomechanical applications. Commercial force sensors are often expensive, with a limited use in severe conditions such as the presence of a strong magnetic field. On the contrary, thin film piezoresistive sensors such as the Tekscan Flexiforce and the Interlink FSR sensors are of low cost and can be considered in such an environment. Only a few information is however available on their dynamic properties. We therefore provide an experimental study of their dynamic behavior, showing nonlinear properties. Identification is then achieved, and a compensation model is proposed. A force control experiment is finally presented to evaluate the compensation scheme.

Needle insertions modelling: Identifiability and limitations

Abstract Soft tissues modeling is a very present preoccupation in different scientific fields, from computer simulation to biomechanics or medical robotics. In this article, we consider the interaction of a needle with living tissues, which is a particularly complex modeling problem since it is characterized by inhomogeneity and nonlinearity properties. We propose a robust method to online estimate the interaction between living tissues and a surgical needle. The ability to obtain physically consistent models during in vivo insertions is discussed.

A robotized positioning platform guided by computed tomography : practical issues and evaluation

Medical robotics is a field where dedicated mechanisms have an increasing importance. The strong operating room constraints, both medical and practical, lead to heavily customized solutions. In this paper, we consider the practical problems that must be solved to build a robotic system dedicated to medical interventions under CT-scan guidance. This compact robotic assistant is placed on the patient what raises new generic robotic design problems. Practical solutions together with the evaluation of a prototype are presented in this paper

Physiological motion rejection in flexible endoscopy using visual servoing and repetitive control : Improvements on non-periodic reference tracking and non-periodic disturbance rejection

Flexible endoscopes are used in many surgical procedures and diagnostic exams, like in gastroscopy or coloscopy. They have also been used recently for new surgical procedures using natural orifices called NOTES. While these procedures are very promising for the patients, they are quite awkward for the surgeons. The flexible endoscope allows the access to operating areas which are not easily reachable, with small or no incisions; but the manipulation of the system is complex. In order to help the practicians during NOTES or classical interventions with flexible endoscopes, we propose to motorize the system so as to partially robotize the movements. This paper presents the problems in the use of the flexible endoscope and explains how the system can be used to stabilize the endoscope on an area of interest despite physiological motions and therefore to improve the manipulation of the system.

User adapted control of force feedback teleoperators: Evaluation and robustness analysis

This paper addresses the influence of human operators on telemanipulators bilateral control. A method to deal with the user variability is proposed, based on the auto-tuning of the force controller at the master side. First, the approach is evaluated experimentally with a group of users in the context of nonlinear interactions with soft tissues, showing very good tracking performances, for both force and position. Second, a robustness analysis is presented that allows to prove the stability of the system for large variations of the behavior of both the environment and the user. This analysis is based on an original uncertain model of the user.

Two-Degrees-of-Freedom Gain Scheduled Control for Quasi-Periodic Disturbance Rejection: Application in the Unwinding of an Eccentric Roll

Abstract This paper presents the design of a gain-scheduled H ∞ controller with two-degrees-of-freedom. The aim is to obtain on the one hand good reference tracking properties and on the other hand to properly reject sinusoidal disturbance in order to suppress vibrations. The frequency of this disturbance is constant or time-varying and unknown but measurable. The proposed approach is based on a time-varying frequency weighting function giving an extended linear parameter varying (LPV) model that is used to design a stabilizing LPV gain-scheduled H ∞ controller. The method is applied to a second order model with output perturbations. This approach is also used to compensate the web tension disturbances caused by the eccentricity of the unwinding roll in a web transport system.

Design of a Magnetic Resonance Imaging-Compatible Cable-Driven Manipulator With New Instrumentation and Synthesis Methods

This paper deals with the design of a cable-driven manipulator (CDM) with instrumented structure for magnetic resonance imaging (MRI)-guided interventions. The strong magnetic field and the limited space inside the scanner constitute two severe design constraints. To handle them, a new synthesis approach for CDM is proposed in order to optimize the device compactness. This approach is based on the use of the zonotope properties to optimize the robot geometry, and the interval analysis tools for its validation. Remote actuation with Bowden cables is considered for MRI-compatibility. High friction along the line transmissions can then be expected which leads to a new instrumentation for cable tension evaluation. A prototype is manufactured and assessed. The principle of the instrumentation is validated as well as the user requirements in terms of workspace and ability to resist to external forces applied by the physician.