Laurence Meylheuc

Design, Development and Preliminary Assessment of Grasping Devices for Robotized Medical Applications

This paper presents the development of NGDs (needle grasping devices) capable of handling elongated objects such as surgical needles. After describing the main demands of medical needle-based procedures, a requirement list for a typical NGD is presented. Some solution principles for a grasping device are generated, combined and then classified to obtain a set of principle variant solutions. The design study of some of these variant solutions is then developed and a discussion on two device candidates constructed using either interconnected rigid bodies or compliant parts will be presented. The mechanical behavior of the compliant mechanism acting on a needle barrel is simulated with a FEM analysis including the model of non-linearities induced by large deformations and the contact between the needle and the grasping device. Functional prototypes of both NGDs have been constructed and a first experimental assessment of their service capability is finally exposed.Copyright

Combining Multi-Material Rapid Prototyping and Pseudo-Rigid Body Modeling for a new compliant mechanism

Multi-Material Rapid Prototyping (MM-RP) is a promising fabrication process for compliant mechanisms, for instance when compactness is a concern. The Pseudo-Rigid Body Model (PRBM) approach is well-known for the synthesis of compliant mechanisms. It is usually based on the use of compliant joints to provide the mechanism mobilities. In this paper, we propose the HSC joint as a new type of revolute compliant joint that is well adapted to MM-RP, and that offers interesting properties in terms of stiffness and range of motion. Based on the HSC joint, a new compliant mechanism, suitable for interventional MRI, is introduced with assessment of a first prototype that is entirely made out of a single polymer part. The interest is twofold. First, the device constitutes a promising solution in this medical context. Second, the impact of the use of MM-RP in combination with PRBM can be evaluated, and their use is discussed as a conclusion.

Design, development and preliminary assessment of a force sensor for robotized medical applications

This paper presents the design, development and the preliminary assessment of a force sensor designed for robotized medical applications. The requirements and constraints for the force sensor are derived from the targeted application of needle insertion in the context of interventional radiology. These constraints rule out the feasibility of commercially available force sensors necessitating the design of a novel force sensor. A discussion on the various force sensing principles utilized in medical robotics and the choice of a suitable sensible principle is done. Next, the solution principles are offered for the design of the flexural element. Starting from the rigid body equivalent, a compliant model of the flexural element is obtained. Simulation using FEM analysis is utilized to verify that the force sensor indeed satisfies the requirements and the constraints of the targeted application. Finally, the calibration and the experimental validation of the force sensor prototype is done using a realistic force profile showing actual force variation during needle insertion.

Design and Modeling of a Polymer Force Sensor

This paper presents the design, modeling, force correction strategies and experimental validation of a force sensor designed for robotized medical applications. The proposed sensor offers a new solution for force measurement in the presence of specific constraints such as medical imaging transparency, limited size, satisfactory rigidity and measurement performance. More specifically, the presented prototype has been purposely adapted to comply with the requirements of needle insertion applications, in the context of interventional radiology. A systematic viscoelastic model identification method is discussed for choosing the best time-dependent model for the force sensor. A novel compensation law is proposed based on the chosen model to correct for the viscoelastic effects of the utilized polymer material. The developed compensation law is inexpensive, stable to noise and can be applied in real-time to the sensor signal. A comparative assessment of the experimental results, obtained from quasi-static to dynamic experiments including harmonic analysis, shows the efficacy of the proposed compensation law, as compared to calibration with static gain and without compensation. The improvement in the sensor response results in decreased hysteresis levels and increased bandwidth, which are improved by more than a factor of 4.

Design and characterization of a novel needle insertion tool

Robotized assistance has been developing constantly in interventional radiology. The recent availability of several commercial systems for treatment planning and needle automatic positioning has even boosted this development. In this paper, we focus on the design of a device dedicated to needle manipulation, a function not included in the available systems. This device is a tool which could be adapted to existing robots, in order to enable them to grasp and insert needles. It is compact and mostly built from polymer parts to cope with the constraints of X-Ray imaging. Each subsystem of the device is separately presented and the system is assessed in order to characterize needle insertion, force measurement, and grasping capabilities.

Phase space identification method for modeling the viscosity of bone cement

A lot of studies have recently emphasized various parameters influencing the viscosity evolution of acrylic bone cement currently used in percutaneous vertebroplasty. Despite all these studies, only very few mathematical models have been proposed to describe the evolution of bone cement viscosity over time. These models are either unexploitable for viscosity control purpose or unable to simultaneously show the viscosity dependence over the most important parameters. In this paper, we propose a new mathematical model of bone cement viscosity obtained through developing a phase space identification method. This model is expressed as a differential equation involving the most important parameters that are temperature and shear rate. In addition to being more complete that the ones already proposed in the literature, it is also easily exploitable for control purpose.

Bone cement modeling for percutaneous vertebroplasty: Bone cement modeling for percutaneous vertebroplasty

Vertebroplasty procedures provide a significant benefit for patients suffering from vertebral fractures. In order to address current issues of vertebroplasty procedures, an injection device able to control the bone cement viscosity has been developed. In addition, this device allows to protect the practitioner by removing him/her from the X-rays area. In this context, a study is first proposed to quantify the bone cement viscosity during its polymerization reaction on a rotational rheometer. These experimental measurements have led to the identification of a complete behavior law that takes into account the simultaneous effects of shear rate, time, and temperature. Based on this preliminary study, this article finally aims to prove the ability of estimating the viscosity of the flowing bone cement on the developed injection system. A final set of experiments validates that the injection device dedicated to vertebroplasty procedures can control the flowing bone cement viscosity by acting on the temperature.

Design and control of a thermal device for bone cement injection

This paper presents an original robotized system that reduces potential bone cement leakage during vertebroplasty procedures while providing a longer injection time to radiologists. The system design meets the requirements of vertebroplasty procedures in terms of injection speed, consumables and medical environment. Our contribution relies on the design, dimensioning and control of a device regulating the injected cement temperature, that is one of the main factors affecting the evolution of the cement viscosity. To control the system, thermal exchanges are first modeled from the physical equations of heat and mass transfer. Then, a simple control method is presented and experimentally assessed to confirm the ability to influence the flowing cement temperature at the center of the stream within an acceptable time.

Robotically assisted injection of orthopedic cement: System design, control and modeling

This study deals with an original biomedical application requiring modeling and control. The general objective is to enable radiologists to inject orthopedic cement under fluoroscopic guidance while protecting themselves from X-rays and having a satisfactory control of the injection. The presented teleoperation system consists in a master and a slave device, designed to perform bilateral teleoperation. This system is controlled using a rate control strategy, so that the operator may manage to perform very slow injections with accuracy and safety. Experiments are performed, not only to confirm the adequacy of the system and the control of the task, but also to provide data in order to characterize the cement injection in realistic conditions. With the aim of controlling, later on, the bone cement viscosity, injection data are used to discuss cement model properties of a cement model.