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ABSTRACT: Having introduced NeuroSim, the prototype of a neurosurgical training simulator at MMVR18, we present our first medical training module. NeuroSim is based on virtual reality and uses real-time algorithms for simulating tissue. It provides a native interface by using a real surgical microscope and original instruments. Having implemented some abstract tasks to train basic skills like hand-eye coordination or the handling of the microscope last year, we now present a medical module where an aneurysm has to be clipped. NeuroSim has been developed in cooperation with the neurosurgical clinic of the University of Heidelberg and VRmagic GmbH in Mannheim.
Studies in health technology and informatics 01/2012; 173:42-7.
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IEEE Transactions on Reliability. 01/2011; 60:351-362.
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ABSTRACT: We present NeuroSim, the prototype of a training simulator for open surgical interventions on the human brain. The simulator is based on virtual reality and uses real-time simulation algorithms to interact with models generated from MRT- or CT-datasets. NeuroSim provides a native interface by using a real surgical microscope and original instruments tracked by a combination of inertial measurement units and optical tracking. Conclusively an immersive environment is generated. In a first step the navigation in an open surgery setup as well as the hand-eye coordination through a microscope can be trained. Due to its modular design further training modules and extensions can be integrated. NeuroSim has been developed in cooperation with the neurosurgical clinic of the University of Heidelberg and the VRmagic GmbH in Mannheim.
Studies in health technology and informatics 01/2011; 163:51-6.
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ABSTRACT: We present a training simulator for indirect ophthalmoscopy. An optical tracking system is used to reconstruct the position of a lens mockup and a model of the patient's face. Refraction and illumination are computed in real-time and displayed on a head-mounted display using augmented reality. A case database completes the training system which allows to practise the examination and to study clinical patterns.
Studies in health technology and informatics 02/2009; 142:295-300.
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ABSTRACT: Endoscopy simulators get more and more common for the training of physicians. It is important to make simulation as realistic as possible by providing optical, acoustical and haptical feedback. The haptic display of our simulator EndoSim allows applying active forces to all degrees of freedom and moving to defined positions. This positioning is used for our automatic guiding system. If the user asks for help, an algorithm calculates how to get over the next barrier, factoring forces and distances. The system is able to decide if it is wise to choose a longer way in order to reduce the force. The user gets either an optical help shown by signs or is guided directly by the automatically moved endoscope. This guiding system is a new possibility for teaching physicians to increase their examination capabilities.
Studies in health technology and informatics 02/2007; 125:385-7.
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ABSTRACT: Real-time tracking of non-rigid objects for use in interfaces of VR-simulators is presented. Markers are attached to the objects and observed by several cameras with integrated image-processing hardware which extracts relevant marker data (centroid, area & color) in real-time. Data from the different cameras is then matched in the host PC to reconstruct the 3D positions. We present two approaches to this special matching problem because standard image feature based algorithms are not feasible for marker-based tracking. A model of the deformation is extracted from the reconstructed 3D point cloud and the simulation model is updated accordingly. Experiments with a prototype of a deformable eye interface for the ophthalmosurgical simulator EYESI show that latency, robustness and accuracy of the deformation tracking are adequate for application in VR simulators. The approach is extensible to other types of simulators where deformable tissue has to be tracked.
Studies in health technology and informatics 01/2007; 125:232-4.
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Biomedical Simulation, Third International Symposium, ISBMS 2006, Zurich, Switzerland, July 10-11, 2006, Proceedings; 01/2006
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ABSTRACT: This paper solves the problem to assign optimal sample sizes to Viola’s stochastic matching [1] and determines the best stochastic
gradient optimizer to this sort of problems. It can be used for applications like X-ray based minimal invasive interventions
or the control of patient motion during radiation therapy. The preprocessing for optimally estimating the parameters lies
between 0.5-4.5 seconds and is only necessary once for a typical set of images to be matched. Matching itself is performed
within 300-1300 milliseconds on an Athlon 800 MHz processor.
09/2004: pages 887-894;
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ABSTRACT: The paper describes three new tissue deformation algorithms. We present a Mass-spring simulation with a quasi-static modification
of the Euler integration to increase the stability of the simulation. A directed length correction for springs and an algorithm
called Dragnet are suggested to enhance propagation of large local displacements through the Mass-spring mesh. The new algorithms
are compared with methods already in use. The combination of Dragnet and the quasi-static Mass-spring modification is used
for the interactive real-time simulation of an ophthalmological procedure, the removal of the Internal Limiting Membrane (ILM).
06/2004: pages 153-160;
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Medical Simulation: International Symposium, ISMS 2004, Cambridge, MA, USA, June 17-18, 2004. Proceedings; 01/2004
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ABSTRACT: The paper discusses rigid registration of a 3D volume to 2D projections based on Mutual-Information similarity measures. The
experiments we conducted are similar to those of Zoellei. However, in order to obtain a stopping criterion we use the Resilient
Backpropagation as optimizer. Performing the registration on artificial images we obtain a speedup of approx. a factor of
10. We applied the matching approach to calibrate C-arm positions and found lateral movements of the detector of 0.5-1 mm
in a given set of projections.
11/2003: pages 161-170;
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Biomedical Image Registration, Second International Workshop, WBIR 2003, Philadelphia, PA, USA, June 23-24, 2003, Revised Papers; 01/2003
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Proceedings of the Seventh International Conference on Digital Image Computing: Techniques and Applications, DICTA 2003, 10-12 December 2003, Macquarie University, Sydney, Australia; 01/2003
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Journal of Visualization and Computer Animation. 01/2003; 14:61-72.
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ABSTRACT: We describe a fast ab initio method for modeling local segments in protein structures. The algorithm is based on a divide and conquer approach and uses a database of precalculated look-up tables, which represent a large set of possible conformations for loop segments of variable length. The target loop is recursively decomposed until the resulting conformations are small enough to be compiled analytically. The algorithm, which is not restricted to any specific loop length, generates a ranked set of loop conformations in 20-180 s on a desktop PC. The prediction quality is evaluated in terms of global RMSD. Depending on loop length the top prediction varies between 1.06 A RMSD for three-residue loops and 3.72 A RMSD for eight-residue loops. Due to its speed the method may also be useful to generate alternative starting conformations for complex simulations.
Protein engineering 05/2002; 15(4):279-86.
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ABSTRACT: The object of this study was to investigate the feasibility of generating a bone surface from data provided by an ultrasound examination and to match this surface with the previous computed tomography (CT) scan.
From a CT data set of a training model of the pelvis, a three-dimensional surface was extracted by global thresholding-based segmentation. The same model was placed in a water basin, and ultrasound images were taken with a guided ultrasound transducer. The three-dimensional surface was generated from the ultrasound data set, and the two surfaces were matched in a semiautomatic mode.
With special segmentation methods, a surface could be extracted automatically from the CT and the ultrasound data set. From these segmented ultrasound slices, a volume data set of the model was generated. After approximate initial matching, the local matching process was completed automatically.
One of the limitations in computer-assisted surgery is the complicated matching process. Using special algorithms, a surface was extracted from the data set of an ultrasound examination and matched in a semiautomatic mode with the surface of a CT data set, facilitating the matching process.
Military medicine 03/2002; 167(2):151-4. · 0.92 Impact Factor
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Commun. ACM. 01/2002; 45:45-49.
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Proceedings of the IASTED International Conference on Visualization, Imaging and Image Processing (VIIP 2001), Marbella, Spain, September 3-5, 2001; 01/2001
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ABSTRACT: The aim of this project is to develop a new approach for the
correction of bone deformities using a computer-aided surgery tool. We
use measurement-based planning of corrections on CT data and an
ultrasound-based navigation system for the real-time support of surgical
operations. We implement a single-cut, close-and-open wedge osteotomy
correction of complex 3D deformities. In the discussed method, virtual
reality and image processing techniques allow planning and supporting of
the operation on a personal computer. The designed software prototype
significantly simplifies the process of osteotomy planning and allows
surgeon training and assistance. The program reduces the total time of
the operation planning and increases the accuracy of the correction
significantly
14th IEEE Symposium on Computer-Based Medical Systems (CBMS 2001), 26-27 July 2001, Bethesda, MD, USA; 01/2001
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Medical Image Computing and Computer-Assisted Intervention - MICCAI'99, Second International Conference, Cambridge, UK, September 19-22, 1999, Proceedings; 01/1999
