Michael Truppe

Virtual image guided navigation in tumor surgery — technical innovation

We present a new visualization system for image-guided stereotactic navigation in tumor surgery. The combination of frameless stereotactic localization technology with real-time video processing permits the visualization of medical imaging data as a video overlay during the actual surgical procedure. Virtual computer-generated anatomical structures are displayed intraoperatively in a semi-immersive head-up display. This results in surgical navigation assistance without limiting the judgement of the physician based on the continuous observation of the operating field. The case presented documents the potential of augmented reality visualization concepts in tumor surgery of the head.

Image-guided surgery

Interventional video tomography (IVT), a new imaging modality, achieves virtual visualization of anatomic structures in three dimensions for intraoperative stereotactic navigation. Partial immersion into a virtual data space, which is orthotopically coregistered to the surgical field, enhances, by means of a see-through head-mounted display (HMD), the surgeons visual perception and technique by providing visual access to nonvisual data of anatomy, physiology, and function. The presented cases document the potential of augmented reality environments in maxillofacial surgery.

Clinical experience with interactive teleconsultation and teleassistance in craniomaxillofacial surgical procedures

PURPOSE The objective of this study was to evaluate the clinical value and feasibility of surgical telenavigation and teleassistance technology in the field of craniomaxillofacial surgery. MATERIALS AND METHODS The technology is based on the principles of augmented reality environment technology and remote stereotactic visualization. A consultant surgeon in a remote location receives video, audio, and stereotactic navigation data from the operation site almost in real-time and, using a head-mounted display, is emerged in the surgical augmented reality environment. By telepresence or teleconsultation, the composite images and superimposed graphics (instruments, target structures, landmarks, contours) can be seen and discussed in connected clinics with the possibility of interactive manipulation and assistance. RESULTS Interactive teleassistance was used in 27 cases of various types craniomaxillofacial surgery. The principles of computer-aided telenavigation were applied successfully. Technical problems in 6 cases did not cause a breakdown of overall system performance. CONCLUSION Teleconsultation with remote experts is a useful tool, although some shortcomings exist. The financial and personal effort involved is considerable.

Remote stereotactic visualization for image-guided surgery: technical innovation.

Additional data from imaging sources using computer navigation assistance enables virtual visualization of anatomical structures in three dimensions for stereotactic navigation during an operation. Recent developments in communication technology enable the broadcasting not only of video data, but also of stereotactic navigation data via the network. By telepresence/teleconsulting, the composite images and overlapping graphics (instrument, target structure, landmark, contour) can be seen in connected clinics, with the possibility of interactive graphic assistance. In cranio-maxillofacial surgery, the first surgical teleconsultation in real time via telecommunication of stereotactic data was performed in August 1996. A patient suffering from a post-traumatic deformity following multiple comminuted midface fractures was re-osteotomized with the aid of image-guided surgery using teleconsultation: the intraoperative position achieved could be discussed with different surgeons with regard to symmetry, hard/soft tissue relationships and occlusal details, with the possibility of on-screen planning interaction and real time evaluation of the results, over a distance of 500 km.

Concepts and results in the development of a hybrid tracking system for CAS

We present the design and the results achieved in the development of a hybrid magneto-optic tracking system suitable for computer aided surgery. Our approach towards a reliable and accurate hybrid position sensor system that is not entirely dependent on an unobstructed line-of-sight between sensor assembly and patient is the combined use of an optical tracker with a direct current (DC) pulsed electromagnetic tracking system (EMTS). The proposed hybridization method aims at providing both accurate and uninterrupted position data by overcoming the drawbacks of both tracking technologies. Results presented include the preliminary assessment of algorithms for fusion of position data from both sensor systems, for calibrating the EMTS to the environment and for detecting systematic distortions in the DC tracking system caused by ferromagnetic materials in order to improve the reliability of the proposed system.

Interventional video tomography

Interventional Video Tomography (IVT) is a new imaging modality for Image Directed Surgery to visualize in real-time intraoperatively the spatial position of surgical instruments relative to the patients anatomy. The video imaging detector is based on a special camera equipped with an optical viewing and lighting system and electronic 3D sensors. When combined with an endoscope it is used for examining the inside of cavities or hollow organs of the body from many different angles. The surface topography of objects is reconstructed from a sequence of monocular video or endoscopic images. To increase accuracy and speed of the reconstruction the relative movement between objects and endoscope is continuously tracked by electronic sensors. The IVT image sequence represents a 4D data set in stereotactic space and contains image, surface topography and motion data. In ENT surgery an IVT image sequence of the planned and so far accessible surgical path is acquired prior to surgery. To simulate the surgical procedure the cross sectional imaging data is superimposed with the digitally stored IVT image sequence. During surgery the video sequence component of the IVT simulation is substituted by the live video source. The IVT technology makes obsolete the use of 3D digitizing probes for the patient image coordinate transformation. The image fusion of medical imaging data with live video sources is the first practical use of augmented reality in medicine. During surgery a head-up display is used to overlay real-time reformatted cross sectional imaging data with the live video image.

Prinzipien der „virtuellen Realität” und deren Anwendung in intraoperativen navigationshilfesystemen

ZusammenfassungGrundlagenDie Technik der „virtuellen Realität” ermöglicht die intraoperative schematische Darstellung von anatomischen und pathologischen Strukturen, von chirurgischen Instrumenten und Implantaten in der Datenbrille des Operateurs.MethodikEin computergestütztes Operationssystem dient der Analyse von digitalisierten radiologischen Daten, der Generierung von Graphiken, die mit diesen Bildern in Überlagerung gebracht werden, und der Visualisierung des gewonnenen Informationskomplexes.ErgebnisseDurch die Navigationshilfestellung kann der Chirurg die Dauer des Eingriffes verkürzen, dessen Präzision erhöhen und die Invasivität minimieren.SchlußlgerungenDer intraoperative Einsatz von computerisierten, bildgestützten Navigationshilfen ist seit langem in der Neurochirurgie bewährt. Die Eingliederung der „Virtual reality”-Technologie eröffnet neue Dimensionen für die minimal invasive Chirurgie im Kopf-Halsbereich.SummaryBackgroundThe “virtual reality” technology allows intraoperative schematic visualization of anatomic and pathologic structures, surgical instruments and implants in the surgeons head-up display.MethodsA computer-based operation system analyzes digitalized radiologic data, generates graphics, which are superimposed on the images, and visualizes the generated information.ResultsWith navigation assistance, the surgeon can shorten the time, improve the precision and minimize the invasivity of the procedure.ConclusionsThe intraoperative use of computerized imageguided navigation systems has proved successful in neurosurgery. The introduction of the “virtual reality” technology opens new dimensions for minimally invasive procedures in the head and neck area

Telenavigation und Expertenkonsultation mit Hilfe eines stereotaktischen Operationsvideoservers

The exponential increase of medical information creates a need for new methods in the visualization of medical imaging modalities for diagnosis and therapy. In this sense, visualization includes the display of medical image data and image-guided stereotaxic navigation as well as the advice of an expert. The Artma Virtual Patient System enables a remote expert to observe the surgical procedure via the Internet and interactively modify the interoperative visualization from the remote location. The expert in the remote location receives the planning data almost in real time over TCP/IP from a stereotaxic videoserver. In addition to live video streaming, stereotaxic navigation data are sent over the network as rigid body coordinates. The expert modifies the surgical simulation on the remote computer and the modified operating plan is sent back to the operating site. By teleconsulting, the composite images and overlapping graphics--instruments, target structures, landmarks, contour--can be seen in affiliated clinics with the possibility of interactive graphical assistance. With this image fusion technology the knowledge of a remote expert is included in virtual data structures and visualized by the overlay with live video data (augmented reality) in real time during surgery.Die exponentielle Zunahme des Informationsflusses in der Medizin verlangt nach neuen Methoden zur Visualisierung patientenbezogener Informationen und Verbreitung von medizinischem Wissen in Diagnose und Therapie. Visualisierung in diesem Sinn beinhaltet die Darstellung medizinischer Bilddaten und bildgeführter stereotaktischer Navigation genauso wie den Rat eines Experten. Das Artma-Virtual-Patient-System ermöglicht einem sich in räumlicher Entfernung befindenden Experten Operationen via Internet mitzuverfolgen und mit Hilfe eines Remote-Computers die interoperative Visualisierung interaktiv zu modifizieren. Der Experte erhält die Planungsdaten nahezu in Echtzeit mittels TCP/IP von einem stereotaktischen Operationsvideoserver. Zusätzlich werden stereotaktische Navigationsdaten als Rigid-body-Koordinaten über das Netzwerk übertragen. Der Experte modifiziert die chirurgische Simulation am Remote-Computer, und der modifizierte Operationsplan wird in den Operationssaal zurückgeschickt. Durch die Telekonsultation können verschiedenartige Bilddaten und überlagerte Graphiken – Instrumente, Zielstrukturen, Landmarken, Konturen – in durch Internet verbundenen Kliniken dargestellt werden, wodurch interaktiv graphische Hilfe angeboten werden kann. Mit Hilfe dieser Bildfusionierungstechnologie werden das nicht vor Ort verfügbare Expertenwissen in virtuelle Datenstrukturen eingebunden und durch Überlagerung mit Livevideo Daten in Echtzeit während der Operation visualisiert. The exponential increase of medical information creates a need for new methods in the visualization of medical imaging modalities for diagnosis and therapy. In this sense, visualization includes the display of medical image data and image-guided stereotaxic navigation as well as the advice of an expert. The Artma Virtual Patient® System enables a remote expert to observe the surgical procedure via the Internet and interactively modify the interoperative visualization from the remote location. The expert in the remote location receives the planning data almost in real time over TCP/IP from a stereotaxic videoserver. In addition to live video streaming, stereotaxic navigation data are sent over the network as rigid body coordinates. The expert modifies the surgical simulation on the remote computer and the modified operating plan is sent back to the operating site. By teleconsulting, the composite images and overlapping graphics –instruments, target structures, landmarks, contour – can be seen in affiliated clinics with the possibility of interactive graphical assistance. With this image fusion technology the knowledge of a remote expert is included in virtual data structures and visualized by the overlay with live video data (augmented reality) in real time during surgery.

Image guided surgery extended by remote stereotactic visualization

In computer aided maxillofacial surgery we have shown the feasibility of computer navigation assistance for a wide variety of indications. Additional data of various imaging sources superimposed during operation with live video from the operating field provide help and useful information even for the experienced surgeon. Rather than the simple identification of target structures in a CT our goal is the intraoperative visualization of complex presurgical simulations of osteotomies of the midface. Because of the interdisciplinary nature the expert needed is not necessarily the surgeon. We present a system (Artma Virtual Patient) that enables a remote expert to observe the surgical procedure via the Internet and interactively modify the intraoperative visualization from his remote location. First results are presented and a live transmission of Stereotactic and video data is established to the conference site.

Biologische Eigenschaften humaner artikulärer Chondrozyten in Zellkultur und der Einfluß auf die autologe Chondrozytentransplantation

ZusammenfassungGrundlagen: Für die biologische Reparatur von lokalisierten Gelenkknorpeldefekten wird auch die Transplantation autologer Chondrozyten verwendet. Ziel der vorliegenden Untersuchung war die Beschreibung der zellbiologischen Grundlagen humaner artikulärer Chondrozyten in Monolayerkultur und deren möglicher Einfluß auf die autologe Chondrozytentransplantation. Methodik: Humane artikuläre Chondrozyten wurden aus Knorpelgewebe enzymatisch isoliert und in Monolayer kultiviert. Die Proliferationsfähigkeit der Zellen wurde mit nichtradioaktiven Proliferationsassays untersucht. Zur Bestimmung des Chondrozyten-Phänotyps wurden immunhistochemische Färbungen durchgeführt. Die Genexpression der Zellen wurde mit der RT-PCR, der Polyacrylamid-Gelelektrophorese und dem Western Blot durchgeführt. Ergebnisse: Die kultivierten Knorpelzellen zeigen bei längerer Kultivierung als Monolayerkultur das Phänomen der Dedifferenzierung, den Verlust ihrer morphologischen, biochemischen und physiologischen Eigenschaften. Frisch isolierte Zellen weisen eine runde oder polygonale Zellform und in der Immunzytochemie eine positive Reaktion mit dem knorpelspezifischem Kollagen Typ II auf. Nach längerer Kultivierung in der Monolayerkultur nehmen die Zellen fibroblastenförmige Gestalt an, zeigen einen Verlust der Kollagen Typ II-Synthese und produzieren das knorpeluntypische Kollagen Typ I. Die m-RNA-Expression zeigt deutliche Unterschiede zwischen primären Chondrozyten und dedifferenzierten Zellen. Diese zeigten einen hohen Übereinstimmungsgrad mit dem Bandmuster kultivierter Fibroblasten. Im Western Blot läßt sich der Wechsel zwischen Typ II und Typ I Kollagen Produktion um den 21. Tag (14–28) der Kultur nachweisen. Schlußfolgerungen: Chondrozyten in Zellkultur unterliegen unter Kulturbedingungen erheblichen regulativen Veränderungen. Die autologe Transplantation kultivierter Chondrozyten kann, solange nicht eindeutig geklärt ist, ob es sich bei den transplantierten Zellen um funktionsfähige Chondrozyten handelt, nicht als gesichert angesehen und kritiklos empfohlen werden. Vor der klinischen Anwendung der autologen Knorpelzelltransplantation sind weitere umfangreiche Grundlagenuntersuchungen notwendig.SummaryBackground: Articular chondrocytes cultured in monolayer are used for the treatment of cartilage defects in human joints. In monolayer culture the cells dedifferentiate and the synthesis of cartilage specific matrix proteins gets lost. Methods: Chondrocyte monolayer cultures were established from small cartilage samples from the macroscopic unchanged areas of femoral heads of patients of after femoral neck fractures and implantation of hip hemiprosthesis. The phenotype of the cultivated chondrocytes was determined with immunocytochemical stainings using monoclonal antibodies against human collagen type I and type II, protein S-100, keratansulfate and vimentin. Collagen I and collagen II synthesis was proved by Western Blot analysis and RT-PCR. Results: Human articular chondrocytes in monolayer culture dedifferentiate and loose their morphological, biochemical, and physiological properties. Freshly isolated cells are rounded shaped and show a positive reaction with cartilage-specific collagen type II antibodies. After the cultivation in monolayer the cells get a fibroblastic-like morphology and produce collagen type I. The m-RNA expression revealed differences between primary chondrocytes and dedifferentiated cells, with high agreement to cultivated fibroblasts. Western blot analysis with collagen type II-specific antibody shows a synthesis of collagen type II until day 28 in monolayer culture. Detection with collagen type I specific antibody indicates the beginning of collagen I synthesis around day 21 in monolayer culture. Conclusions: Freshly isolated human articular chondrocytes express cartilage-specific Collagen type II and continue to do so for several days in primary monolayer culture. The “switch” from Collagen type II to Collagen type I synthesis during monolayer culture of these aged cells was found around day 21 (range 14 to 28). The general recommendation of autologous chondrocyte transplantation for the treatment of articular cartilage defects is only justified after further basic research for the determination of the nature of the transplanted cells.