Navigations- und AR - Visualisierungssystem für den Einsatz bei minimalinvasiven, unfallchirurgischen Operationen (NARVIS)

The NARVIS Project has been successfully completed in 2007.

From the annual report of Bayerische Forschungsstiftung (BFS) (2007):

Ziel der Entwicklung des Navigations- und Visualsierungssystems NARVIS war, eine dreidimensionale In-situ-Visualisierung für die minimalinvasive Unfallchirurgie zu schaffen. Dabei soll ein Head-Mounted Display (HMD) dem Arzt präoperative Bilddaten im Arbeitsbereich darstellen. Im Gegensatz zu klassischen Mehrschirmlösungen erlaubt die Erweiterung (Augmentierung) der Sicht auf den Operationssitus dem Chirurgen, sich auf die Operation zu konzentrieren. Dazu bietet sie ihm neben erweiterten Ansichtsmöglichkeiten auch Zusatzinformationen und Navigationshilfen bei schwierigen Eingriffen. Im Projekt sollte geprüft werden, inwieweit sich die HMD-Visualisierungstechnologie für derartige Anwendungen eignet und in den klinischen Arbeitsablauf integrieren lässt.

Nach der Systemplanung durch Mediziner und Ingenieure wurde ein erster Prototyp gebaut, der bei einer Reihe von experimentellen Operationen erprobt und in Design, Handhabung und Funktionalität nach den Verbesserungsvorschlägen der Mediziner weiter optimiert wurde. Dabei stellte sich heraus, dass die derzeitige HMD-Technik aufgrund von Gewicht und mangels Tragekomfort nicht durchgehend während einer OP getragen werden kann. Genauere Workflow-Analysen halfen bei der Identifizierung von Arbeitsabschnitten, in denen NARVIS nützlich sein kann. Auch wenn sich die HMD-Technik für einen direkten klinischen Einsatz noch besser an die klinischen Anforderungen anpassen muss, kann NARVIS in der chirurgischen Ausbildung schon wertvolle Dienste leisten, etwa wenn es von einem auszubildenden Mediziner getragen wird, der die Operation vor Ort verfolgt. Das rege Interesse an NARVIS bei Konferenzen und Vorführungen legt nahe, dass der Ansatz weiterverfolgt werden sollte – von technischen Verbesserungen würde er unmittelbar profitieren.

NARVIS sketch

NARVIS Related Publications

Find here a list of selected publications that are related to the NARVIS Project.

NARVIS Related Projects

The following projects have been started based on the objectives of the NARVIS Project that has been successfully completed in 2007.

NARVIS - navigated augmented reality visualization system
Advanced visualization is getting increasingly important for the operation room of the future. The increasing number of available medical images must be presented to surgery team in new ways in order to support them rather than overloading with more information. In our project NARVIS we integrate an HMD-based (head mounted display) AR system into the operation room for 3D in situ visualization of computed tomography (CT) images. The final system aims at spinal surgery. The work is in close collaboration with our project partners “Klinikum für Unfallchirgie” at LMU, A.R.T. Weilheim, and Siemens Corporate Research in Princeton. The project is funded by Bayerische Forschungsstiftung.

Augmented Reality Magic Mirror using the Kinect
The Kinect allows tracking of users without additional markers. We develop a magic mirror that generated an overlay of a video image with volume visualization from a CT volume. Such a system could be used for education of anatomy.

ARAV Augmented Reality Aided Vertebroplasty
In today’s ORs more and more operations are performed employing minimally invasive procedures. Surgical instruments are inserted through a tiny cut on the patient’s skin, the port to the inside of the patient. In some cases endoscope cameras record video images of the operation site that are presented on a monitor. As a consequence of this technique, the surgeon’s field of view is divided into several work spaces, the monitor, the patient and information of medical imaging data presented on a third station. The missing direct view on the workspace complicates intuitive control of surgical tools. In contrast to open surgery the physician has to collect information from several fields of view at the same time and fuse information mentally to create a complete model of his working space, the operation site. The minimally invasive intervention vertebroplasty was determined as a suitable medical application to bring an Head Mounted Display (HMD) into the OR for augmentation of surgical instruments and medical imaging data. In-situ visualization with an HMD presents all available imaging data and navigational information in one field of view. The objective of vertebroplasty is the insertion of cement into weak and brittle vertebrae through a trocar for stabilization. In this case the view on the inside of the patient is not provided by an endoscope camera. However, since the operation is performed under a CT scanner, imaging data is permanently updated to check position of the trocar and amount of inserted cement. Imaging data is presented on a monitor and has to be mapped mentally by the surgeon on the real operation site.

Virtual Mirror: Interaction Paradigm for Augmented Reality Applications
Augmented Reality offers a higher degree of freedom for the programmer than classical visualization of volume data on a screen. The existing paradigms for interaction with 3D objects are not satisfactory for particular applications since the majority of them rotate and move the object of interest. The classic manipulation of virtual objects cannot be used while keeping real and virtual spaces in alignment within an AR environment. This project introduces a simple and efficient interaction paradigm allowing the users to interact with 3D objects and visualize them from arbitrary viewpoints without disturbing the in-situ visualization, or requiring the user to change the viewpoint. We present a virtual, tangible mirror as a new paradigm for interaction with 3D models. The concept borrows its visualization paradigm in some sense from methodology used by dentists to examine the oral cavity without constantly changing their own viewpoint or moving the patients head. The virtual mirror improves the understanding of complex structures, enables completely new concepts to support navigational aid for different tasks and provides the user with intuitive views on physically restricted areas.

Improving Depth Perception and Perception of Layout for In-Situ Visualization in Medical Augmented Reality
In-situ visualization in medical augmented reality (AR) using for instance a video see-through head mounted display (HMD) and an optical tracking system enables the stereoscopic view on visualized CT data registered with the real anatomy of a patient. Data can aligned with the required accuracy and the surgeons do not have to analyze data on an external monitor or images attached to the wall somewhere in the operating room. Thanks to a medical AR system like mentioned before, surgeons get a direct view onto and also ”into” the patient. Mental registration of medical imagery with the operation site is not necessary anymore. In addition surgical instruments can be augmented inside the human body. Bringing medical imagery and surgical instruments in the same field of action provides the most intuitive way to understand the patient’s anatomy within the region of interest and allows for the development of completely new generations of surgical navigation systems.
Unfortunately, this method of presenting medical data suffers from a serious lack. Virtual imagery, such as a volume rendered spinal column, can only be displayed superimposed on real objects. If virtual entities of the scene are expected behind real ones, like the virtual spinal column beneath the real skin surface, this problem implicates incorrect perception of the viewed objects respective their distance to the observer. The strong visual depth cue interposition is responsible for misleading depth perception. This project aims at the development and evaluation of methods to improve depth perception for in-situ visualization in medical AR. Its intention is to provide an extended view onto the human body that allows an intuitive localization of visualized bones and tissue.

Augmented Reality Supported Patient Education and Consultation
The project Augmented Reality Supported Patient Education and Consultation (Augmented Reality unterstützte Operationsaufklärung) aims at developing Augmented Reality (AR) supported communication tools for patient education. The development of the targeted systems involves disciplines reaching from image registration, human computer interaction and in-situ visualization to instructional design and perceptual psychology. As a primary clinical application, we determined breast reconstruction in plastic surgery.

MeTaTop A Multi Sensory Table Top System for Medical Procedures
A tabletop system in medical environments can be used for interactive and collaborative analysis of patient data but also as a multimedia user interface within sterile space. For preoperative planning physicians in charge with a particular patient meet to discuss the medical case and plan further steps for therapy. For this reason, they could collaboratively view and browse through all kind of available medical imaging data with the tabletop system. Alternatively such a system could be a central interaction device for all kind of equippment within the OR requiring user input, however, can not be operated by the sterile surgeon. We believe that the projection of all kind of user and information interfaces on a sterile glass plane would facilitate the clinical workflow.
This project is strongly related to the Tangible Interaction Surface for Collaboration between Humans project.

3D user interfaces for medical interventions
This work group aims at practical user interfaces for 3D imaging data in surgery and medical interventions. The usual monitor based visualization and mouse based interaction with 3D data will not present acceptable solutions. Here we study the use of head mounted displays and advanced interaction techniques as alternative solutions. Different issues such as depth perception in augmented reality environment and optimal data representation for a smooth and efficient integration into the surgical workflow are the focus of our research activities. Furthermore appropriate ways of interaction within the surgical environment are investigated.

Laparoscope Augmentation for Minimally Invasive Liver Resection
In recent years, an increasing number of liver tumor indications were treated by minimally invasive laparoscopic resection. Besides the restricted view, a major issue in laparoscopic liver resection is the precise localization of the vessels to be divided. To navigate the surgeon to these vessels, pre-operative imaging data can hardly be used due to intra-operative organ deformations caused by appliance of carbon dioxide pneumoperitoneum and respiratory motion.

Therefore, we propose to use an optically tracked mobile C-arm providing cone-beam computed tomography imaging capability intra-operatively. After patient positioning, port placement, and carbon dioxide insufflation, the liver vessels are contrasted and a 3D volume is reconstructed during patient exhalation. Without any further need for patient registration, the volume can be directly augmented on the live laparoscope video. This augmentation provides the surgeon with essential aid in the localization of veins, arteries, and bile ducts to be divided or sealed.

Current research focuses on the intra-operative use and tracking of mobile C-arms as well as laparoscopic ultrasound, augmented visualization on the laparoscope's view, and methods to synchronize respiratory motion.

2012
	L. Wang, P. Fallavollita, R. Zou, X. Chen, S. Weidert, N. Navab Closed-form inverse kinematics for interventional C-arm X-ray imaging with six degrees of freedom: modeling and application IEEE Transactions on Medical Imaging (to appear). (bib)
2011
	M. Wieczorek, A. Aichert, P. Fallavollita, O. Kutter, A. Ahmadi, L. Wang, N. Navab Interactive 3D visualization of a single-view X-Ray image Proceedings of Medical Image Computing and Computer-Assisted Intervention (MICCAI 2011), Toronto, Canada, September 2011. (bib)
	S. Weidert, L. Wang, P. Thaller, J. Landes, A. Brand, N. Navab, E. Euler X-ray Stitching for Intra-operative Mechanical Axis Determination of the Lower Extremity the 11th Annual Meeting of the International Society for Computer Assisted Orthopaedic Surgery, London, UK, June 15-19 2011 (bib)
	L. Wang, R. Zou, S. Weidert, J. Landes, E. Euler, D. Burschka, N. Navab Closed-form inverse kinematics for intra-operative mobile C-arm positioning with six degrees of freedom SPIE Medical Imaging, Lake Buena Vista (Orlando), Florida, USA, February 2011 (bib)
2010
	C. Bichlmeier Immersive, Interactive and Contextual In-Situ Visualization for Medical Applications Dissertation an der Fakultät für Informatik, Technische Universität München, 2010 ( online version available here) (bib)
	L. Wang, M. Springer, H. Heibel, N. Navab Floyd-Warshall All-Pair Shortest Path for Accurate Multi-Marker Calibration The 9th IEEE and ACM International Symposium on Mixed and Augmented Reality, Seoul, Korea, Oct. 13 - 16, 2010. (bib)
	T. Blum, M. Wieczorek, A. Aichert, R. Tibrewal, N. Navab The effect of out-of-focus blur on visual discomfort when using stereo displays The 9th IEEE and ACM International Symposium on Mixed and Augmented Reality, Seoul, Korea, Oct. 13 - 16, 2010. The original publication is available online at ieee.org. (bib)
	C. Bichlmeier, E. Euler, T. Blum, N. Navab Evaluation of the Virtual Mirror as a Navigational Aid for Augmented Reality Driven Minimally Invasive Procedures The 9th IEEE and ACM International Symposium on Mixed and Augmented Reality, Seoul, Korea, Oct. 13 - 16, 2010. The original publication is available online at ieee.org. (bib)
	L. Wang, R. Zou, S. Weidert, J. Landes, E. Euler, D. Burschka, N. Navab Modeling Kinematics of Mobile C-arm and Operating Table as an Integrated Six Degrees of Freedom Imaging System The 5th International Workshop on Medical Imaging and Augmented Reality, MIAR 2010, Beijing, China, September 19-20, 2010 (bib)
	A. Ahmadi, F. Pisana, E. DeMomi ^?, N. Navab, G. Ferrigno User friendly graphical user interface for workflow management during navigated robotic-assisted keyhole neurosurgery Computer Assisted Radiology (CARS), 24th International Congress and Exhibition, Geneva, CH, June 2010 (bib)
	L. Wang, J. Traub, S. Weidert, S.M. Heining, E. Euler, N. Navab Parallax-Free Intra-Operative X-ray Image Stitching the MICCAI 2009 special issue of the Journal Medical Image Analysis (bib)
	L. Wang, J. Landes, S. Weidert, T. Blum, A. von der Heide, E. Euler, N. Navab First Animal Cadaver Study for Interlocking of Intramedullary Nails under Camera Augmented Mobile C-arm A Surgical Workflow Based Preclinical Evaluation the 1st International Conference on Information Processing in Computer-Assisted Interventions (IPCAI), Switzerland, June 23 2010. The original publication is available online at www.springerlink.com. (bib)
	S. Weidert, L. Wang, J. Landes, A. von der Heide, N. Navab, E. Euler First Surgical Procedures under Camera-Augmented Mobile C-arm (CamC ^?) guidance The 3rd Hamlyn Symposium for Medical Robotics ,London, UK, May 25 2010 (bib)
	A. Plate, A. Ahmadi, T. Klein, N. Navab, J. Weiße, J. Mehrkens, K. Bötzel Towards a More Objective Visualization of the Midbrain and its Surroundings Using 3D Transcranial Ultrasound 54. Jahrestagung der Deutschen Gesellschaft für Klinische Neurophysiologie und Funktionelle Bildgebung (DGKN), Halle, GER, March 2010 (bib)
	P. Wucherer, C. Bichlmeier, M. Eder, L. Kovacs, N. Navab Multimodal Medical Consultation for Improved Patient Education Proceedings of Bildverarbeitung fuer die Medizin (BVM 2010), Aachen, Germany, March 2010 (bib)
	M. Wieczorek, A. Aichert, O. Kutter, C. Bichlmeier, J. Landes, S.M. Heining, E. Euler, N. Navab GPU-accelerated Rendering for Medical Augmented Reality in Minimally-Invasive Procedures Proceedings of Bildverarbeitung fuer die Medizin (BVM 2010), Aachen, Germany, March 14-16 2010 (bib)
	P. Dressel, L. Wang, O. Kutter, J. Traub, S.M. Heining, N. Navab Intraoperative positioning of mobile C-arms using artificial fluoroscopy SPIE Medical Imaging, San Diego, California, USA, February 2010 (bib)
2009
	C. Bichlmeier, S.M. Heining, L. Omary, P. Stefan, B. Ockert, E. Euler, N. Navab MeTaTop: A Multi-Sensory and Multi-User Interface for Collaborative Analysis of Medical Imaging Data Interactive Demo (ITS 2009), Banff, Canada, November 2009 (bib)
	C. Bichlmeier, S. Holdstock, S.M. Heining, S. Weidert, E. Euler, O. Kutter, N. Navab Contextual In-Situ Visualization for Port Placement in Keyhole Surgery: Evaluation of Three Target Applications by Two Surgeons and Eighteen Medical Trainees The 8th IEEE and ACM International Symposium on Mixed and Augmented Reality, Orlando, US, Oct. 19 - 22, 2009. (bib)
	C. Bichlmeier, M. Kipot, S. Holdstock, S.M. Heining, E. Euler, N. Navab A Practical Approach for Intraoperative Contextual In-Situ Visualization International Workshop on Augmented environments for Medical Imaging including Augmented Reality in Computer-aided Surgery (AMI-ARCS 2009), London, UK, September 2009 (bib)
	C. Bichlmeier, S.M. Heining, M. Feuerstein, N. Navab The Virtual Mirror: A New Interaction Paradigm for Augmented Reality Environments IEEE Trans. Med. Imag., vol. 28, no. 9, pp. 1498-1510, September 2009 (bib)
	L. Wang, J. Traub, S. Weidert, S.M. Heining, E. Euler, N. Navab Parallax-free Long Bone X-ray Image Stitching Medical Image Computing and Computer-Assisted Intervention (MICCAI), London, UK, September 20-24 2009 (bib)
	A. Ahmadi, T. Klein, N. Navab Advanced Planning and Ultrasound Guidance for Keyhole Neurosurgery in ROBOCAST Russian Bavarian Conference (RBC), Munich, GER, July 2009 (bib)
	A. Ahmadi, T. Klein, N. Navab, R. Roth, R.R. Shamir, L. Joskowicz, E. DeMomi ^?, G. Ferrigno, L. Antiga, R.I. Foroni Advanced Planning and Intra-operative Validation for Robot-Assisted Keyhole Neurosurgery In ROBOCAST International Conference on Advanced Robotics (ICAR), Munich, GER, June 2009 (bib)
	B. Ockert, C. Bichlmeier, S.M. Heining, O. Kutter, N. Navab, E. Euler Development of an Augmented Reality (AR) training environment for orthopedic surgery procedures Proceedings of The 9th Computer Assisted Orthopaedic Surgery (CAOS 2009), Boston, USA, June, 2009 (bib)
	N. Navab, S.M. Heining, J. Traub Camera Augmented Mobile C-arm (CAMC): Calibration, Accuracy Study and Clinical Applications IEEE Trans. Med. Imag., to appear (bib)
	L. Wang, J. Traub, S.M. Heining, S. Benhimane, R. Graumann, E. Euler, N. Navab Long Bone X-ray Image Stitching using C-arm Motion Estimation Proceedings of Bildverarbeitung fuer die Medizin (BVM 2009), Heidelberg, Germany, March 22-24 2009 (bib)
	L. Wang, S. Weidert, J. Traub, S.M. Heining, C. Riquarts, E. Euler, N. Navab Camera Augmented Mobile C-arm: Towards Real Patient Study Proceedings of Bildverarbeitung fuer die Medizin (BVM 2009), Heidelberg, Germany, March 22-24 2009 (bib)
2008
	C. Bichlmeier, B. Ockert, S.M. Heining, A. Ahmadi, N. Navab Stepping into the Operating Theater: ARAV - Augmented Reality Aided Vertebroplasty The 7th IEEE and ACM International Symposium on Mixed and Augmented Reality, Cambridge, UK, Sept. 15 - 18, 2008. (bib)
	J. Traub New Concepts for Design and Workflow Driven Evaluation of Computer Assisted Surgery Solutions Dissertation an der Fakultät für Informatik, Technische Universität München, 2008 ( online version available here) (bib)
	O. Kutter, A. Aichert, C. Bichlmeier, J. Traub, S.M. Heining, B. Ockert, E. Euler, N. Navab Real-time Volume Rendering for High Quality Visualization in Augmented Reality International Workshop on Augmented environments for Medical Imaging including Augmented Reality in Computer-aided Surgery (AMI-ARCS 2008), USA, New York, September 2008 (bib)
	C. Bichlmeier, B. Ockert, O. Kutter, M. Rustaee, S.M. Heining, N. Navab The Visible Korean Human Phantom: Realistic Test & Development Environments for Medical Augmented Reality International Workshop on Augmented environments for Medical Imaging including Augmented Reality in Computer-aided Surgery (AMI-ARCS 2008), USA, New York, September 2008 (bib)
	J. Traub, A. Ahmadi, N. Padoy, L. Wang, S.M. Heining, E. Euler, P. Jannin, N. Navab Workflow Based Assessment of the Camera Augmented Mobile C-arm System International Workshop on Augmented Reality environments for Medical Imaging and Computer-aided Surgery (AMI-ARCS 2008), New York, NY, USA, September 2008 (bib)
	L. Wang, J. Traub, S.M. Heining, S. Benhimane, R. Graumann, E. Euler, N. Navab Long Bone X-ray Image Stitching Using Camera Augmented Mobile C-arm Medical Image Computing and Computer-Assisted Intervention, MICCAI, 2008, New York, USA, September 6-10 2008 (bib)
	F. Wimmer, C. Bichlmeier, S.M. Heining, N. Navab Creating a Vision Channel for Observing Deep-Seated Anatomy in Medical Augmented Reality Proceedings of Bildverarbeitung fuer die Medizin (BVM 2008), Munich, Germany, April 2008 (bib)
	J. Traub, S.M. Heining, E. Euler, N. Navab Two camera augmented mobile C-arm – System setup and first experiments Proceedings of The 8th Computer Assisted Orthopaedic Surgery (CAOS 2008), Hong Kong, China, June, 2008 (bib)
	S.M. Heining, C. Bichlmeier, E. Euler, N. Navab Smart Device: Virtually Extended Surgical Drill Proceedings of The 8th Computer Assisted Orthopaedic Surgery (CAOS 2008), Hong Kong, China, June, 2008 (bib)
	T. Sielhorst New Methods for Medical Augmented Reality Dissertation an der Fakultät für Informatik, Technische Universität München, 2008 ( online version available here) (bib)
2007
	C. Bichlmeier, S.M. Heining, M. Rustaee, N. Navab Laparoscopic Virtual Mirror for Understanding Vessel Structure: Evaluation Study by Twelve Surgeons The Sixth IEEE and ACM International Symposium on Mixed and Augmented Reality, Nara, Japan, Nov. 13 - 16, 2007. (bib)
	C. Bichlmeier, F. Wimmer, S.M. Heining, N. Navab Contextual Anatomic Mimesis: Hybrid In-Situ Visualization Method for Improving Multi-Sensory Depth Perception in Medical Augmented Reality The Sixth IEEE and ACM International Symposium on Mixed and Augmented Reality, Nara, Japan, Nov. 13 - 16, 2007. (bib)
	T. Sielhorst, Wu Sa, A. Khamene, F. Sauer, N. Navab Measurement of absolute latency for video see through augmented reality Sixth IEEE and ACM International Symposium on Mixed and Augmented Reality (ISMAR'07), Nara, Japan, November 2007 (bib)
	T. Sielhorst, M. Bauer, O. Wenisch, G. Klinker, N. Navab Online Estimation of the Target Registration Error for n-ocular Optical Tracking Systems to appear Proceedings of Medical Image Computing and Computer-Assisted Intervention (MICCAI 2007), Brisbane, Australia, October 2007 (bib)
	P. Stefan, J. Traub, S.M. Heining, C. Riquarts, T. Sielhorst, E. Euler, N. Navab Hybrid navigation interface: a comparative study Proceedings of Bildverarbeitung fuer die Medizin (BVM 2007), Munich, Germany, March 2007, pp. 81-86 (bib)
	C. Bichlmeier, T. Sielhorst, S.M. Heining, N. Navab Improving Depth Perception in Medical AR: A Virtual Vision Panel to the Inside of the Patient Proceedings of Bildverarbeitung fuer die Medizin (BVM 2007), Munich, Germany, March 2007 (bib)
2006
	C. Bichlmeier, N. Navab Virtual Window for Improved Depth Perception in Medical AR International Workshop on Augmented Reality environments for Medical Imaging and Computer-aided Surgery (AMI-ARCS 2006), Copenhagen, Denmark, October 2006 (bib)
	J. Traub, P. Stefan, S.M. Heining, T. Sielhorst, C. Riquarts, E. Euler, N. Navab Hybrid navigation interface for orthopedic and trauma surgery Proceedings of Medical Image Computing and Computer-Assisted Intervention (MICCAI 2006), Copenhagen, Denmark, October 2006, pp. 373-380 (bib)
	T. Sielhorst, C. Bichlmeier, S.M. Heining, N. Navab Depth perception a major issue in medical AR: Evaluation study by twenty surgeons Proceedings of Medical Image Computing and Computer-Assisted Intervention (MICCAI 2006), Copenhagen, Denmark, October 2006, pp. 364-372 The original publication is available online at www.springerlink.com (bib)
	J. Traub, P. Stefan, S.M. Heining, T. Sielhorst, C. Riquarts, E. Euler, N. Navab Towards a Hybrid Navigation Interface: Comparison of a Slice Based Navigation System with In-situ Visualization Proceedings of International Workshop on Medical Imaging and Augmented Reality (MIAR 2006), Shanghai, China, August, 2006, pp.179-186 (bib)
	S.M. Heining, P. Stefan, L. Omary, S. Wiesner, T. Sielhorst, N. Navab, F. Sauer, E. Euler, W. Mutschler, J. Traub Evaluation of an in-situ visualization system for navigated trauma surgery Journal of Biomechanics 2006; Vol. 39 Suppl. 1, page 209 (bib)
	J. Traub, P. Stefan, S.M. Heining, T. Sielhorst, C. Riquarts, E. Euler, N. Navab Stereoscopic augmented reality navigation for trauma surgery: cadaver experiment and usability study International Journal of Computer Assisted Radiology and Surgery, 2006; Vol. 1 Suppl. 1, page 30 - 31. The original publication is available online at www.springerlink.com (bib)
	T. Sielhorst, M. Feuerstein, J. Traub, O. Kutter, N. Navab CAMPAR: A software framework guaranteeing quality for medical augmented reality International Journal of Computer Assisted Radiology and Surgery, 2006; Vol. 1 Suppl. 1, page 29 - 30. The original publication is available online at www.springerlink.com (bib)
	S.M. Heining, P. Stefan, F. Sauer, E. Euler, N. Navab, J. Traub Evaluation of an in-situ visualization system for navigated trauma surgery Proceedings of The 6th Computer Assisted Orthopaedic Surgery (CAOS 2006), Montreal, Canada, June, 2006 (bib)