Jörg Raczkowsky

A safe robot system for craniofacial surgery

The ultimate ambition of a robotic system in surgical theater has to be the safety of the involved humans: patient, physicians, nurses. In order to provide that claim the criteria of ergonomics, redundancy, short reaction time, and accuracy must be met. In contrast to many other surgical robotic applications we are studying complex bone cut trajectories which require several distinct orientations of the robot tool and milling cutter, respectively. Exact bone cuts are especially needed for bone repositionings placed at the human skull in craniofacial surgery. Therefore, the system has to be flexible enough to keep the capability of changing the patients position during the intra-operative phase. This paper introduces the overall concept and realization of the system.

Synthesis of CAD/CAM, robotics and biomaterial implant fabrication: single-step reconstruction in computer aided frontotemporal bone resection

The preoperative manufacturing of individual skull implants, developed by an interdisciplinary research group at Ruhr-University Bochum, is based on the use of titanium as the most common material for implants at present. Using the existing technology for materials that can be milled or moulded, customized implants may be manufactured as well. The goal of the study was to examine biodegradable materials and to evaluate the practicability of intraoperative instrument navigation and robotics. Data acquisition of an adult sheeps head was performed with helical computer tomography (CT). The data were transferred onto a computer aided design/computer aided manufacturing system (CAD/CAM system), and two complex defects in the frontotemporal skull were designed. Standard individual titanium implants were milled for both of the defects. Additionally, for one of the defects a resection template, as well as a mould for the biodegradable poly(D,L-lactide) (PDLLA) implant, were fabricated by the CAD/CAM system. A surgeon carried out the first bone resection (#1) for the prefabricated titanium implant using the resection template and an oscillating saw. The robot system Stäubli RX90CR, modified for clinical use, carried out the other resection (#2). Both titanium implants and the PDLLA implant were inserted in their respective defects to compare the precision of their fit. A critical comparison of both implant materials and both resection types shows that fabrication of a PDLLA implant and robot resection are already possible. At present, the titanium implant and resection using a template are more convincing due to the higher precision and practicability.

Development and First Patient Trial of a Surgical Robot for Complex Trajectory Milling

Objective: Todays surgical robots normally perform “simple” trajectories, e.g., assisting as tool-holding devices in neurosurgery, or milling linear paths for cavities in total hip replacement. From a clinical point of view, it is still a complex undertaking to implement robots in the operating room. Until now, robot systems have not been used in patient trials to mill “complex” trajectories, which involve many positional and orientation changes and are often necessary in cranio-maxillofacial (CMF) surgery. This paper presents the RobaCKa surgical robot system, which allows more precise execution of surgical interventions and milling of “complex” trajectories. Materials and Methods: The main components of the RobaCKa system are a (former) CASPAR robot system, a POLARIS system, and a force-torque sensor. Results: In the first patient trial (April 2003) the planned trajectory was executed with an error of 0.66 ± 0.2 mm. Conclusions: The use of former industrial robots for surgical applications is possible but complex. The advantages are improved precision and quality and the possibility of documentation. The use of such systems is normally limited to research institutions or large clinics, because it is hardly possible to implement the necessary technical and logistic efforts in routine surgical work.

Operation planning of robot supported surgical interventions

Presents a new operation planning system which enables a surgeon to plan and perform complex robot-supported surgical interventions. The system has been evaluated in the Clinic for Cranio-Maxillo-Facial Surgery at the University of Heidelberg. In contrast to commercial systems, our goal was that the system should consider the complete surgical intervention and not just a single procedure of it. A second goal was that the system should enable the management of complex operations, independent of which way the intervention is intra-operatively performed (without technical support, with passive navigation support or with active support by robots). Our system supports the surgeon during pre-operative planning as well as during the intra-operative execution phase. Therefore, we developed a model of the course of operation by which the management of surgical interventions is made possible. The focus of this paper is on this course model. First, we introduce instruction graphs and describe the structure of each activity, observing its attributes and their context. Additionally, various surgical scopes are presented which enable the surgeon to select one view among different ones in the individual operation procedures, in accordance with medical and technical knowledge as well as in accordance with different degrees of abstraction. Finally, we demonstrate the realisation of the introduced course model in our operation planning system and present first results in clinical practice.

Ein Robotersystem für craniomaxillofaciale chirurgische Eingriffe.

Zusammenfassung. In industriellen Anwendungen bewähren sich Roboter durch ihre hohe Präzision und Wiederholgenauigkeit. Ihr Einsatz in neuen Gebieten, wie z.B. in der Chirurgie unterliegt aber anderen Randbedingungen. Die Datenakquisition und Planung jedes Eingriffs muß individuell für einen Patienten ausgeführt werden. Die präoperative Planung einer Operation auf den komplexen Freiformflächen des Patienten ist nur mit der Unterstützung eines rechnerbasierten Planungssystems durchführbar. Durch eine integrierte intraoperative Instrumentennavigation wird sichergestellt, daß die geplanten Vorgänge auch geometrisch richtig ausgeführt werden. Eine prototypische Roboterarbeitszelle dient zur Evaluierung der untersuchten Methoden und entwickelten Subsysteme. Die vorgestellten Arbeiten finden im Rahmen des Sonderforschungsbereiches 414: “Rechner- und sensorgestützte Chirurgie” statt, der eine enge interdisziplinäre Zusammenarbeit zwischen Ingenieuren, Medizinern und Naturwissenschaftlern ermöglicht.Abstract. In industrial applications robots prove successful due to their high precision and their repetition accuracy. However, when used in new fields, e. g. in surgery, other conditions apply. The acquisition of data and the planning of each operation must be carried out individually for a patient. The preoperative planning of an operation on the complex free forming surfaces of a patient can only be realised with the support of a computer based planning system. An integrated intraoperative instrument navigation ensures that the planned proceedings are performed geometrically correct. A prototypical robot cell evaluates the examined methods and developed subsystems. The presented studies are carried out within the framework of the Sonderforschungsbereich 414 “Computer and sensor supported surgery” which allows a close interdisciplinary cooperation between engineers, doctors and scientists.

System Design of a Hand-Held Mobile Robot for Craniotomy

This contribution reports the development and initial testing of a Mobile Robot System for Surgical Craniotomy, the Craniostar. A kinematic system based on a unicycle robot is analysed to provide local positioning through two spiked wheels gripping directly onto a patients skull. A control system based on a shared control system between both the Surgeon and Robot is employed in a hand-held design that is tested initially on plastic phantom and swine skulls. Results indicate that the system has substantially lower risk than present robotically assisted craniotomies, and despite being a hand-held mobile robot, the Craniostar is still capable of sub-millimetre accuracy in tracking along a trajectory and thus achieving an accurate transfer of pre-surgical plan to the operating room procedure, without the large impact of current medical robots based on modified industrial robots.

Planning and simulation of microsurgical laser bone ablation.

PurposeLaser ablation of hard tissue is not completely understood until now and not modeled for computer-assisted microsurgery. A precise planning and simulation is an essential step toward the usage of microsurgical laser bone ablation in the operating room.MethodsPlanning the volume for laser bone ablation is based on geometrical definitions. Shape and volume of the removed bone by single laser pulses were measured with a confocal microscope for modeling the microsurgical ablation. To remove the planned volume and to achieve smooth surfaces, a simulation of the laser pulse distribution is developed.ResultsThe confocal measurements show a clear dependency from laser energy and resulting depth. Two-dimensional Gaussian functions are fitting in these craters. Exemplarily three ablation layers were planned, simulated, executed and verified.ConclusionsTo model laser bone ablation in microsurgery the volume and shape of each laser pulse should be known and considered in the process of ablation planning and simulation.

Multi kinect people detection for intuitive and safe human robot cooperation in the operating room

Microsoft Kinect cameras are widely used in robotics. The cameras can be mounted either to the robot itself (in case of mobile robotics) or can be placed where they have a good view on robots and/or humans. The use of cameras in the surgical operating room adds additional complexity in placing the cameras and adds the necessity of coping with a highly uncontrolled environment with occlusions and unknown objects. In this paper we present an approach that accurately detects humans using multiple Kinect cameras. Experiments were performed to show that our approach is robust to interference, noise and occlusions. It provides a good detection and identification rate of the user which is crucial for safe human robot cooperation.

A supervision system for the intuitive usage of a telemanipulated surgical robotic setup

This paper introduces the OP:Sense system that is able to track objects and humans and. To reach this goal a complete surgical robotic system is built up that can be used for telemanipulation as well as for autonomous tasks, e.g. cutting or needle-insertion. Two KUKA lightweight robots that feature seven DOF and allow variable stiffness and damping due to an integrated impedance controller are used as actuators. The system includes two haptic input devices for providing haptic feedback in telemanipulation mode as well as including virtual fixtures to guide the surgeon even during telemanipulation mode. The supervision system consists of a marker-based optical tracking system, Photonic Mixer Device cameras (PMD) and rgb-d cameras (Microsoft Kinect). A simulation environment is constantly updated with the model of the environment, the model of the robots and tracked objects, the occupied space as well as tracked models of humans.

Visual servoing of a laser ablation based cochleostomy

The aim of this study is a defined, visually based and camera controlled bone removal by a navigated CO2 laser on the promontory of the inner ear. A precise and minimally traumatic opening procedure of the cochlea for the implantation of a cochlear implant electrode (so-called cochleostomy) is intended. Harming the membrane linings of the inner ear can result in damage of remaining organ functions (e.g. complete deafness or vertigo). A precise tissue removal by a laser-based bone ablation system is investigated. Inside the borehole the pulsed laser beam is guided automatically over the bone by using a two mirror galvanometric scanner. The ablation process is controlled by visual servoing. For the detection of the boundary layers of the inner ear the ablation area is monitored by a color camera. The acquired pictures are analyzed by image processing. The results of this analysis are used to control the process of laser ablation. This publication describes the complete system including image processing algorithms and the concept for the resulting distribution of single laser pulses. The system has been tested on human cochleae in ex-vivo studies. Further developments could lead to safe intraoperative openings of the cochlea by a robot based surgical laser instrument.