Jürgen Wahrburg

Position control of a surgical robot by a navigation system

In orthopaedic surgery, the development of computer based new technologies such as navigation systems and robotics will facilitate more precise, reproducible results of surgical interventions. There are already commercial systems available for clinical use which, however, still have some limitations and drawbacks. Most of them can only be applied in a very narrow application range and it is not possible to use them in less or minimal invasive surgery because they need large incisions for a rigid bone fixation to avoid patient movements. This paper presents a new modular surgical assistant system. The surgical robot, which is one part of the system, is position controlled by a navigation system to detect and compensate small patient movements automatically. By this approach optimal tool position can be maintained ail the time during the surgery without additional rigid bone or patient fixation. A modular tool system and an open modular software architecture facilitates an easy adjustment to support various surgical procedures especially in less invasive surgery.

A Navigated Mechatronic System with Haptic Features to Assist in Surgical Interventions

Objective: In orthopaedic surgery, the development of new computer-based technologies such as navigation systems and robotics will facilitate more precise, reproducible results in surgical interventions. There are already commercial systems available for clinical use, though these still have some limitations and drawbacks. This paper presents an alternative approach to a universal modular surgical assistant system for supporting less or minimally invasive surgery. Materials and Methods: The position of a mechatronic arm, which is part of the system, is controlled by a navigation system so that small patient movements are automatically detected and compensated for in real time. Thus, the optimal tool position can be constantly maintained without the need for rigid bone or patient fixation. Furthermore, a force control mode of the mechatronic assistant system, based on a force-torque sensor, not only increases safety during surgical interventions but also facilitates hand-driven direct positioning of the arm. Results: A prototype has been successfully tested in clinical applications at the Orthopädische Universitätsklinik Frankfurt. For the firsttime worldwide, implantation of the cup prosthesis in total hip replacement surgery has been carried out with the assistance of a mechatronic arm. According to measurements by the digitizing system, operating tool angle deviation remained below 0.5°, relative to the preoperative planning. Conclusion: The presented approach to a new kind of surgical mechatronic assistance system supports the surgeon as needed by optimal positioning of the surgical instruments. Due to its modular design, it is applicable to a wide range of tasks in surgical interventions, e.g., endoscope guidance, bone preparation, etc.

Virtual fixtures with autonomous error compensation for human–robot cooperative tasks

This paper presents a control strategy for surgical interventions, applied on a human–robot cooperative system, which facilitates the sharing of responsibilities between surgeon and robot. The controller utilizes virtual fixtures to constrain the movements of the end-effector into a predefined path or region. Possible deviation error can be compensated in two different ways: (a) manual compensation and (b) autonomous compensation. With manual compensation, the system defines both virtual fixtures and error compensation directions, but the surgeon must apply manual forces himself/herself in order to generate end-effector motion. With autonomous compensation, a clear distribution of responsibilities between surgeon and robotic system is present, meaning the surgeon has complete control of the end-effector along the preferred directions, while the robot autonomously compensates for any deviation along the non-preferred directions.

Concept of a novel laser probe for minimal invasive applications in neurosurgery

The design is described of a novel stereotactic probe for minimal invasive, laser-based treatment of deep seated brain lesions. The probe is coupled to a Nd:YLF laser system which generates laser pulses with a pulse width of only a few picoseconds. These pulses initiate a plasma-induced tissue ablation process that offers significant advantages in neurosurgical applications because it causes no unwanted thermal or mechanical side effects. Furthermore, the probe is connected to an irrigation and pressure control system which is needed to support the laser-based tissue destruction. All major components of the probe as well as its operation as a stereotactic device are illustrated. A nearly finalized prototype has a diameter of 5.5 mm and may be inserted into the skull up to a depth of 12 cm.

Control Concepts for Industrial Robots Equipped with Multiple and Redundant Sensors

Although in recent years the automation of industrial production was marked by a continual increase in the use of industrial robots, more complex types of problems such as assembly and machining have rarely been solved with the aid of robot until today. The reasons for this, apart from the more or less satisfying performance characteristics of available sensors, are above all the unsolved questions concerning the interface between the sensors and the robot control systems.

Komponenten und Architektur eines navigierten Assistenzroboters für chirurgische Anwendungen (Components and Architecture of a Navigated Robot System for Surgical Applications)

Abstract Der Beitrag beschreibt ein universelles Chirurgieassistenzsystem, das durch die Kombination von Navigation und Robotik gekennzeichnet ist und eine neue, in hohem Maße interaktive Arbeitsweise der Roboter-Komponente realisiert. Damit wird es möglich, die spezifischen Vorteile beider Systemkomponenten auszunutzen: Das Navigationssystem dient zur genauen und schnellen Registrierung der Patientenanatomie mit Hilfe eines elektro-optischen 3D-Digitalisiersystems, während der Roboterarm als mechatronische Ergänzung der Navigation zur Führung und Positionierung der chirurgischen Instrumente eingesetzt wird und Probleme durch Abrutschen oder Zittern vermeidet. Außerdem ist es möglich, den Roboterarm bei kleinen Patientenbewegungen on-line nachzuführen, sodass die räumliche Zuordnung zwischen Patientenstruktur und chirurgischem Werkzeug stets erhalten bleibt. In diesem Beitrag wird vor allem die erzielbare statische Systemgenauigkeit diskutiert.

Untersuchung optischer 3D Messsysteme zum Einsatz in der computerassistierten Chirurgie

Zusammenfassung Optische 3D Messsysteme bilden wesentliche Komponenten, um in der computerassistierten Chirurgie die räumliche Lage chirurgischer Instrumente im Bezug auf den Patienten fortlaufend zu erfassen. In diesem Beitrag wird ein auf diese Anwendung zugeschnittener Versuchsaufbau vorgestellt, der die Untersuchung der Genauigkeit optischer, markerbasierter 3D Lokalisiersysteme ermöglicht. Zur berührungslosen Erfassung der Patientenanatomie wird außerdem ein robotergeführter Laserscanner beschrieben, bei dem durch Auswertung der Kamera-Rohdaten des Lokalisiersystems die Laserlinie detektiert wird. Abstract Optical 3D measurement systems are essential components for applications in computer assisted surgery to permanently acquire the spatial position of surgical instruments with regard to the patients anatomy. This paper presents an experimental setup which is tailored to this application. It evaluates the accuracy of marker-based optical 3D localization systems. In addition a robot-guided laser scanner for touchless registration of the patients anatomy is described where the laser line can be detected by analysing the camera raw data of the localization system.

Design of smart tools to support pre- and intra-operative use of surgical navigation systems

Abstract In this paper we present novel solutions to support the application of computer assisted surgical interventions in which optical surgical navigation systems based on stereo cameras are used. The objective is to improve both the pre-operative setup and the intra-operative use of the navigation system. Following a short introduction describing the potential for improvements of existing navigation systems new approaches and the components to implement them are described. The pre-operative alignment of the stereo camera is made easier by attaching a small graphic display to its tripod which can show how much of the operating area is covered by the measurement volume of the camera. The intra-operative application is improved by a mechanism for motorized camera motions in order to follow the position of surgical instruments. Furthermore a small display can be attached to a surgical instrument which clearly indicates to the surgeon how to guide the instrument in order to stay on the planned trajectory.

Methods to determine the scaling factor in X-ray images for exact preoperative planning in hip surgery

Abstract This article presents common methods for calculating the scaling factor in X-ray images and reveals their basic technical difficulties, accuracy and error sources. Further, the causes for magnification of patient anatomy in X-ray images are described. Preoperative planning by means of X-ray images, its difficulties, reliability and limitations are also illustrated. Additionally, a new approach is introduced which is based on a stereo camera system used to identify the magnification especially in anterior-posterior pelvis images for hip application, considering the geometry of X-ray apparatus while minimizing errors by foreclosing the well-known central issues of all the conventional methods for the most part.

Feasibility Study on Online Guiding of Industrial Robot by Experimentally Created Force/Torque Map for Peg-in-Hole Assembling

The experiment carried in this paper aims to study the feasibility of controlling an industrial robot to carry Peg-in-Hole assembling task using what called a Force/Torque Map. This type of control is based on real-time F/T sensor data during contact between the peg and the hole. The F/T Map presents the data acquired during previous attempts of the assembly task.