Hans-Joachim Bender

Biomechanical Simulation of the Vitreous Humor in the Eye Using and Enhanced ChainMail Algorithm

The focus of this paper is the newly developed Enhanced ChainMail Algorithm that will be used for modeling the vitreous humor in the eye during surgical simulation. The simulator incorporates both visualization and biomechanical modeling of a vitrectomy, an intra-ocular surgical procedure for removing the vitreous humor. The Enhanced ChainMail algorithm extends the capabilities of an existing algorithm for modeling deformable tissue, 3D ChainMail, by enabling the modeling of inhomogeneous material. In this paper, we present the enhanced algorithm and demonstrate its capabilities in 2D.

Using Computer Simulation in Operating Room Management: Impacts on Process Engineering and Performance

Operating rooms are regarded as the most costly hospital facilities. Due to rising costs and decreasing reimbursements, it is necessary to optimize the efficiency of the operating room suite. In this context several strategies have been proposed that optimize patient throughput by redesigning perioperative processes. The successful deployment of effective practices for continuous process improvements in operating rooms can require that operating room management sets targets and monitors improvements throughout all phases of process engineering. Simulation can be used to study the effects of process improvements through novel facilities, technologies and/or strategies. In this paper, we propose a conceptual framework to use computer simulations in different stages of business process management (BPM) lifecycle for operating room management. Additionally, we conduct simulation studies in different stages of the BPM lifecycle. The results of our studies provide evidence that simulation can provide effective decision support to drive performance in operating rooms in several phases of the BPM lifecycle

Reconstruction of 3D Catheter Paths from 2D X-Ray Projections

The diagnosis and therapy of intensive care patients requires the usage of several catheters inside the patients chest. The information about the position and path of the catheters inside the patients body is important for the doctor, but is nowadays not part of the clinical routine. One possible source of this information are CT or NMR scans, which lead to an organizational overhead and additional stress for the intensive care patient. To minimize the overhead we implemented an algorithm to extract the 3D path of catheters in the body of the patient from two or more standard X-ray images. The approach is based on only few assumptions, runs completely in three dimensions, and uses the X- ray images only as a guideline for the path reconstruction process. It shows an inherently robust behaviour against misleading structures in the X-ray images, like loops and intersections. The algorithm has been tested with a selection of test images, including images from the clinical routine.

Amantadine Sulfate Reduces Experimental Sensitization and Pain in Chronic Back Pain Patients

We investigated if established psychophysical measures of enhanced experimental sensitization in chronic musculoskeletal pain can be reduced by adjuvant treatment with a N-methyl-d-aspartate receptor antagonist, amantadine sulfate, and whether a reduction in sensitization might be accompanied by a concurrent improvement in clinical pain. Sensitization was evaluated by an experimental tonic heat model of short-term sensitization with concurrent subjective and behavioral psychophysical scaling. Twenty-six patients with chronic back pain were included in the randomized, double-blind, placebo-controlled study and received daily dosages of either placebo or 100 mg of amantadine sulfate during a 1-wk treatment. Participants completed quantitative sensory testing of pain thresholds and experimental sensitization before and after treatment and clinical pain ratings before, during, and after treatment. Experimental sensitization and clinical pain were reduced in patients receiving verum. Initially, experimental sensitization was enhanced in patients, with early sensitization at nonpainful intensities of contact heat and enhanced sensitization at painful intensities, as shown previously. After 1 wk of treatment, experimental sensitization was reduced with amantadine sulfate but not with placebo. We conclude that adjuvant chronic pain treatment with N-methyl-d-aspartate receptor antagonists might be beneficial for chronic pain if enhanced sensitization is involved and that the quantitative sensory test of temporal summation may be used to verify this.

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.

Status quo and current trends of operating room management in Germany.

Purpose of review Ongoing healthcare reforms in Germany have required strenuous efforts to adapt hospital and operating room organizations to the needs of patients, new technological developments, and social and economic demands. This review addresses the major developments in German operating room management research and current practice. Recent findings The introduction of the diagnosis-related group system in 2003 has changed the incentive structure of German hospitals to redesign their operating room units. The role of operating room managers has been gradually changing in hospitals in response to the change in the reimbursement system. Operating room managers are today specifically qualified and increasingly externally hired staff. They are more and more empowered with authority to plan and control operating rooms as profit centers. For measuring performance, common perioperative performance indicators are still scarcely implemented in German hospitals. In 2008, a concerted time glossary was established to enable consistent monitoring of operating room performance with generally accepted process indicators. These key performance indicators are a consistent way to make a procedure or case – and also the effectiveness of the operating room management – more transparent. Summary In the presence of increasing financial pressure, a hospitals executives need to empower an independent operating room management function to achieve the hospitals economic goals. Operating room managers need to adopt evidence-based methods also from other scientific fields, for example management science and information technology, to further sustain operating room performance.

How work context affects operating room processes: using data mining and computer simulation to analyze facility and process design.

The complexity of the operating room (OR) requires that both structural (eg, department layout) and behavioral (eg, staff interactions) patterns of work be considered when developing quality improvement strategies. In our study, we investigated how these contextual factors influence outpatient OR processes and the quality of care delivered. The study setting was a German university-affiliated hospital performing approximately 6000 outpatient surgeries annually. During the 3-year-study period, the hospital significantly changed its outpatient OR facility layout from a decentralized (ie, ORs in adjacent areas of the building) to a centralized (ie, ORs in immediate vicinity of each other) design. To study the impact of the facility change on OR processes, we used a mixed methods approach, including process analysis, process modeling, and social network analysis of staff interactions. The change in facility layout was seen to influence OR processes in ways that could substantially affect patient outcomes. For example, we found a potential for more errors during handovers in the new centralized design due to greater interdependency between tasks and staff. Utilization of the mixed methods approach in our analysis, as compared with that of a single assessment method, enabled a deeper understanding of the OR work context and its influence on outpatient OR processes.

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.

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.