Joerg Raczkowsky

Ex vivo accuracy evaluation for robot assisted laser bone ablation

Cutting bony tissue using short‐pulsed laser ablation enables contact‐free processing in arbitrary shapes and with considerably smaller incision widths compared with mechanical tools. This precise method necessitates assistance by robotic surgery.

Sensor-aided Milling with a Surgical Robot System

In this paper sources of errors are pointed out that occur using a robot system in order to cut bones. It is shown that the deflection of the robot tool must not be neglected if an accuracy in the range of one millimeter (from planning to execution) is required, since the tool deflection is up to 1.5 millimeters depending on the affecting torques. Therefore, special focus is set on methods which cope with this problem. A calibration approach considering the deflection of the robot tool is presented. After this calibration, it is possible to consider the tool deflection during the registration procedure (ball-in-cone strategy) as well as during the intervention. Furthermore, a discrete feed control algorithm is outlined.

End-effector calibration and registration procedure for robot assisted laser material processing: Tailored to the particular needs of short pulsed CO 2 laser bone ablation

Material processing using a laser has become a widely used method for industrial procedures (e.g. laser welding or cutting). Furthermore the medical laser has become an integral part of dermatology, neurosurgery, ENT, esthetic, plastic and general surgery. Recent publications have shown, that the short pulsed CO2 laser is suitable to ablate bony and cartilage tissue and proposes fundamentally new operative techniques in medicine. The obtainable precision in cutting (in the hundred micrometers range) with a laser system can only be reached using means of computer and robot assisted surgery. We established the first robot assisted laser bone ablation setup, comprising a prototype CO2 laser system and a six degree of freedom robot. The laser beam is guided through a passive articulated mirror arm to the robots end-effector. The endeffector is composed of a two mirror galvanometric scan head, which deflects the pulsed laser beam onto the tissue. In this paper we present an end-effector calibration and registration method to determine the parameters which are critical in obtaining precise and accurate cutting results.

High precision cochleostomy by use of a pulsed CO2 laser - an experimental approach.

Abstract A precise cochleostomy is a crucial step in cochlear implantation, particularly if residual hearing is to be preserved. A contactless ablation of the promontory bone by a pulsed CO2 laser system seems to be a promising approach. The bone is removed by a scan head controlled laser beam in sequential scan cycles with a pulse rate of 50–100 μs. Digital picture analysis and pattern detection are used to identify the membranous lining of the cochlea. We achieved a bone ablation in a micrometer range per scan cycle with the laser. A perforation of the promontory bone could be detected by automatic pattern detection. The enhancement of automatic pattern detection can lead to a minimally invasive, function-preserving laser cochleostomy. Copyright

Application of contract-based verification techniques for hybrid automata to surgical robotic systems

Surgical robotic systems have to deliver a high quality of safety, since they deal with human lives. Their safety specifications must ensure the absence of risks for the patient and the operating room staff. To respect the modular nature of a surgical system, we propose a contract based verification approach for safety. We introduce a case study based on a typical surgical robotic operation scenario and model its components by using hybrid automata. We exploit the theory of parallel composition of contracts to verify properties on each component and prove that the property of the overall system can be obtained by composition.

Mixed Reality Neurosurgical Microscope for Training and Intra-operative Purposes

In recent years, neurosurgery has been deeply influenced by new technologies. It requires fine techniques targeted to obtain treatments minimally invasive though often traumatic. The precision of the surgical gesture is related both to experience of the surgeon and accuracy of the available technological instruments. Computer Aided Surgery (CAS) can offer several benefits for the patients safety. From a technological point of view we observe the use of the Virtual Reality (VR) for the surgeons training and Augmented Reality (AR) for the intra-operative aid for treatments. This paper presents a prototype for a mixed reality system for neurosurgical interventions embedded on a real surgical microscope for pre- and intra- operative purposes. Its main purposes are: the realistic simulation (visual and haptic) of the spatula palpation of low-grade glioma and also the stereoscopic visualization in AR of relevant 3D data for safe surgical movements in the image guided interventions.

Evaluation of a computer aided planning and surgical robot system for craniofacial surgery

Craniofacial surgery requires skillful and experienced surgeons. Due to the vicinity to vital parts and the great impact of bone repositionings at the complex anatomic structures of the skull, the interventions have to be conducted with high precision. Therefore, we have developed two systems: KasOp, an operation planning system on the basis of 3D-patient-models and RobaCKa, a surgical robot system. After several tests using dummies and animal experiments, which prove the overall system to be safe and accurate, a first test has been conducted on a human test subject.

Low-distortion perturbative solutions in a camera calibration model including high-distortion radial effects.

PurposeAn endoscope fisheye lens camera calibration model was extended using intuitive vector parameters to describe lens distortion with a fourth degree radial polynomial.MethodAn existing algorithm was expanded to the wider domain of applicability of the high endoscopic distorted lenses. By completely decoupling the computation of the camera distortion center obtained using general properties of distortion lines, even strong radial distortion effects can be perturbatively included into a pure perspective first guess zero-distortion solution.ResultsA perturbative and iterative solution used to model small amounts of lens distortion can be maintained in case of strong distortion lenses, such as the endoscope fisheye, with satisfactory results.ConclusionWe demonstrated that using an educated guess for the initial solution based on the final location of the lens distortion center, the intuitive vector-based model’s full solution can be iteratively obtained starting from a purely perspective distortion-free first guess solution.

Methods for end-effector coupling in robot assisted interventions

Robot assisted interventions often require coupling and decoupling of the robot to/from a specific tool. By using manual gripper changing systems these operations are facilitated, but the robot has to approach to and move away from the coupling position. Industrial applications are mostly based on movements which are teached-in, since the working environment is perfectly described (i.e. working cell). Especially in robot assisted surgery we are facing non fixed tools to which the robot has to be coupled (e.g. a holding device attached to a mobilised bone) and restricted working areas with special safety requirements. In this paper we present an automatic end-effector registration method and a semiautomatic coupling procedure exemplarily for robot assisted orthognathic surgery. By using means of an optical localisation system and force- /torque sensing, the coupling procedure is controlled by a multi- sensor data fusion approach. The developed methods can be adapted to any robot assisted intervention.

Pre-programmed robotic osteotomies for fibula free flap mandible reconstruction: A preclinical investigation

Bony free flap reconstruction of the facial skeleton remains a challenging area of reconstructive surgery. Despite technological advances that have aided planning and execution of these procedures, surgical inaccuracy is not insignificant. One source of error that has not been wholly addressed is that attributable to a human operator. In this study, we investigate the feasibility and accuracy of performing osteotomies robotically in pre‐programmed fashion for fibula free flap mandible reconstruction as a method to reduce inaccuracies related to human error. A mandibular defect and corresponding free fibula flap reconstruction requiring six osteotomies were designed on a CAD platform. A methodology was developed to translate this virtual surgical plan data to a robot (KUKA, Augsburgs, Germany), which then executed osteotomies on three‐dimensional (3D) printed fibula flaps with the aid of dynamic stereotactic navigation. Using high‐resolution computed tomography, the osteotomized segments were compared to the virtually planned segments in order to measure linear and angular accuracy. A total of 18 robotic osteotomies were performed on three 3D printed fibulas. Compared to the virtual preoperative plan, the average linear variation of the osteotomized segments was 1.3 ± 0.4 mm, and the average angular variation was 4.2 ± 1.7°. This preclinical study demonstrates the feasibility of pre‐programmed robotic osteotomies for free fibula flap mandible reconstruction. Preliminarily, this method exhibits high degrees of linear and angular accuracy, and may be of utility in the development of techniques to further improve surgical accuracy.