Markus A. Schill

Intraocular surgery on a virtual eye

The EyeSi surgical simulation immerses the surgeon in an environment of real surgical instruments, virtual tissue deformations, and interactive 3D graphics.

EyeSi - A Simulator for Intra-ocular Surgery

We present a computer-based medical workstation for the simulation of a vitrectomy that allows training and rehearsal of eye surgeons. The surgeon manipulates two original instruments inside a cardanically suspended mechanical model of the eye. The instrument positions are tracked by CCD cameras and monitored by a PC which then renders the scenery using a computer graphical model of the eye and the instruments. Stereoscopic images are presented to the user through two small LCD displays that are mounted to the system and emulate the stereo microscope used in real operations. The simulator offers the training of intra-ocular navigation as well as first approaches to interaction with pathological tissues using mass-spring and 3D-ChainMail models. All operations (tracking, rendering, collision detection, tissue manipulation) are computed in real-time on a PC.

Collision detection and tissue modeling in a VR-simulator for eye surgery

This paper gives a survey of techniques for tissue interaction and discusses their application in the context of the intra-ocular training system EyeSi. As key interaction techniques collision detection and soft tissue modeling are identified. For collision detection in EyeSi, an enhanced image-based approach for collisions between deformable surfaces and rigid objects is presented. By exploiting the computing power of graphics processing units, it achieves higher performance than existing geometry-based approaches. Deformation vectors are computed and used for the biomechanical model. A mass-spring approach is shown to be powerful enough to bridge the gap between low computational demands and a convincing tissue behavior.

Virtuelle Realitäten für die augenchirurgische Ausbildung

ZusammenfassungVorgestellt wird ein computergestützter, medizinischer Simulator, der die Durchführung virtueller Augenoperationen ermöglicht. Der Operateur arbeitet dabei mit Originalinstrumenten an einem mechanischen Auge. Neben dem Training der Navigation im Auge wird aufgrund enthaltener biomechanischer Modelle die Interaktion mit pathologischen Strukturen im Auge ermöglicht. Der Simulatoraufbau umfasst ein Modell des Operationstisches, ein mechanisches Auge, 3 CCD-Kameras zur Positionsbestimmung, das am Ort des Mikroskops fixierte Stereodisplay und einen Computer. Die Bewegung der Instrumente und des mechanischen Auges werden von Kameras erfasst und an den Computer übermittelt. Die Kombination von 2 Kamerabildern erlaubt über stereoskopische Rückprojektion die Berechnung der Positionen im Raum. Aus den Positionsdaten berechnet ein PC die Reaktion des Gewebes und ein computergrafisches Modell der Szenerie. Statt des Stereomikroskops verwendet der Simulator 2 kleine LCD-Monitore, die durch Okulare betrachtet werden und stereoskopische Bilder liefern. Die Simulation läuft mit einer Wiederholrate von mindestens 20 Hz.AbstractWe present a computer-based medical training workstation for the simulation of intraocular eye surgery. The surgeon manipulates two original instruments inside a mechanical model of the eye. The instrument positions are tracked by CCD cameras and monitored by a PC which renders the scenery using a computer-graphic model of the eye and the instruments. The simulator incorporates a model of the operation table, a mechanical eye, three CCD cameras for the position tracking, the stereo display, and a computer. The three cameras are mounted under the operation table from where they can observe the interior of the mechanical eye. Using small markers the cameras recognize the instruments and the eye. Their position and orientation in space is determined by stereoscopic back projection. The simulation runs with more than 20 frames per second and provides a realistic impression of the surgery. It includes the cold light source which can be moved inside the eye and the shadow of the instruments on the retina which is important for navigational purposes.

Clinical Efficacy of Simulated Vitreoretinal Surgery to Prepare Surgeons for the Upcoming Intervention in the Operating Room

Purpose To evaluate the efficacy of the virtual reality training simulator Eyesi to prepare surgeons for performing pars plana vitrectomies and its potential to predict the surgeons’ performance. Methods In a preparation phase, four participating vitreoretinal surgeons performed repeated simulator training with predefined tasks. If a surgeon was assigned to perform a vitrectomy for the management of complex retinal detachment after a surgical break of at least 60 hours it was randomly decided whether a warmup training on the simulator was required (n = 9) or not (n = 12). Performance at the simulator was measured using the built-in scoring metrics. The surgical performance was determined by two blinded observers who analyzed the video-recorded interventions. One of them repeated the analysis to check for intra-observer consistency. The surgical performance of the interventions with and without simulator training was compared. In addition, for the surgeries with simulator training, the simulator performance was compared to the performance in the operating room. Results Comparing each surgeon’s performance with and without warmup trainingshowed a significant effect of warmup training onto the final outcome in the operating room. For the surgeries that were preceeded by the warmup procedure, the performance at the simulator was compared with the operating room performance. We found that there is a significant relation. The governing factor of low scores in the simulator were iatrogenic retinal holes, bleedings and lens damage. Surgeons who caused minor damage in the simulation also performed well in the operating room. Conclusions Despite the large variation of conditions, the effect of a warmup training as well as a relation between the performance at the simulator and in the operating room was found with statistical significance. Simulator training is able to serve as a warmup to increase the average performance.

Biomechanical simulation of the Falx cerebri using the finite element method

A method is introduced which uses a biomechanical model of the Falx cerebri (F.c.) to determine the pressure difference in the scull that is necessary for a shunting of the F.c. It therefore allows a correction of ICP measured in one hemisphere to the ICP in the other one.

A Handheld Robot for Orthopedic Surgery - ITD

This paper describes the specification and development of the handheld medical robot ITD for orthopedic surgery. The robot compensates unintended movements of the surgeon and the patient and thus stabilizes the relative position of a drilling tool to the bone. To do so a highly dynamic but lightweight robot is held in the surgeon’s hand and a special occlusion-robust tracking system provides fast and accurate position information. Additionally an inertial tracking system is implemented in the robot. To prove the system’s functionality, experiments with polystyrene foam have been carried out with the first prototype based on the hexapod kinematics. A second prototype provides higher dynamics, lower outlines and weight and is based on the Hexaglide kinematics. Both robots are still too large for routine surgical use but prove good potential for future developments.

A Modular Scalable Approach to Occlusion-Robust Low-Latency Optical Tracking

An advanced optical tracking system for computer assisted surgery (CAS) is presented. The system supports an arbitrary number of cameras that may be placed at suitable positions e.g. fixed cameras at the ceiling of the operating theater or movable cameras on the operating lamps. The modular scalable system architecture reduces occlusion problems and allows adaptation to tracking scenarios of different complexity. The camera modules each integrate hardware-based image processing to allow for low latency of 10ms required in demanding applications like robot control. As a first application tracking of a handheld robotic manipulator has been implemented.