Basic research and 12 years of clinical experience in computer-assisted navigation technology: a review.

Computer-aided surgical navigation technology is commonly used in craniomaxillofacial surgery. It offers substantial improvement regarding esthetic and functional aspects in a range of surgical procedures. Based on augmented reality principles, where the real operative site is merged with computer generated graphic information, computer-aided navigation systems were employed, among other procedures, in dental implantology, arthroscopy of the temporomandibular joint, osteotomies, distraction osteogenesis, image guided biopsies and removals of foreign bodies. The decision to perform a procedure with or without computer-aided intraoperative navigation depends on the expected benefit to the procedure as well as on the technical expenditure necessary to achieve that goal. This paper comprises the experience gained in 12 years of research, development and routine clinical application. One hundred and fifty-eight operations with successful application of surgical navigation technology--divided into five groups--are evaluated regarding the criteria "medical benefit" and "technical expenditure" necessary to perform these procedures. Our results indicate that the medical benefit is likely to outweight the expenditure of technology with few exceptions (calvaria transplant, resection of the temporal bone, reconstruction of the orbital floor). Especially in dental implantology, specialized software reduces time and additional costs necessary to plan and perform procedures with computer-aided surgical navigation.

Changes in the ratio of type-I and type-II collagen expression during monolayer culture of human chondrocytes.

We compared the changes in the ratio of type-I and type-II collagen in monolayer cultures of human articular chondrocytes (HAC). HAC were isolated from samples of cartilage from normal joints and cultivated in monolayer for up to 46 days. Expression of collagen type-I and type-II was determined by immunocytochemistry, Western blotting, and the nested reverse transcription polymerase chain reaction (RT-PCR), and quantified by real-time PCR. The transition from a spherical morphology to the flattened morphology of an anchorage-dependent culture was accompanied by a rapid change in the collagen phenotype with the replacement of collagen type II by collagen type I. This was confirmed by immunocytochemistry and Western blotting between days 21 and 28. Using techniques for the analysis of gene transcription (nested RT-PCR and real-time PCR), a complete switch of collagen gene expression was not observed. Expression of collagen type I increased 100-fold during the culture time. That of collagen type II was found during the entire period and decreased more than 100-fold. The main finding was that expression of the genes encoding collagen type I and II was highly time-dependent and the ratio of collagen type II to I (CII/CI), defined as an index of cell differentiation, was significantly higher (215- to 480-fold) at the beginning of the culture. At the end of the experimental culture time, ratios between 0.1 and 1 were reached.

Collagen expression in tissue engineered cartilage of aged human articular chondrocytes in a rotating bioreactor.

This study describes the culture and three-dimensional assembly of aged human articular chondrocytes under controlled oxygenation and low shear stress in a rotating-wall vessel. Chondrocytes cultured in monolayer were released and placed without any scaffold as a single cell suspension in a rotating bioreactor for 12 weeks. Samples were analyzed with immunohistochemistry, molecular biology and electron microscopy. During serial monolayer cultures chondrocytes dedifferentiated to a "fibroblast-like" structure and produced predominantly collagen type I. When these dedifferentiated cells were transferred to the rotating bioreactor, the cells showed a spontaneous aggregation and formation of solid tissue during the culture time. Expression of collagen type II and other components critical for the extracellular cartilage matrix could be detected. Transmission electron microscopy revealed a fine network of randomly distributed collagen fibrils. This rotating bioreactor proves to be a useful tool for providing an environment that enables dedifferentiated chondrocytes to redifferentiate and produce a cartilage-specific extracellular matrix.

[Stereotactic telepresence in otorhinolaryngologic surgery]. / Stereotaktische Telepräsenz in der Hals-, Nasen- und Ohrenchirurgie.

BACKGROUND: Intraoperative three-dimensional (3D) navigation systems determine spatial positions and visualize them in radiological data sets. Usually, data from 3-D computed tomography (CT) are used. We have successfully implemented "augmented reality" in routine clinical practice by superimposing positional data and guiding and ancillary structures on the live endoscopic video of the operating site. Thus, optimal access paths and anatomical structures such as the a. carotis interna or the n. opticus can be displayed. METHODS AND RESULTS: With modern telecommunication, any two locations can be connected for intraoperative consultations with a remote expert, and 3D navigation is an ideal complement. We have successfully tested telephone, ISDN, Ethernet, and ATM technology intraoperatively and find that the ARTMA system provides well-developed technology. CONCLUSIONS: Stereotactic telepresence can provide essential aid in difficult surgical procedures, and the ARTMA Knowledge-Guided Surgery system will contribute further to the optimization of computer-assisted surgery.

A full 3D-navigation system in a suitcase.

OBJECTIVE: To reduce the impact of contemporary 3D-navigation systems on the environment of typical otorhinolaryngologic operating rooms, we demonstrate that a transfer of navigation software to modern high-power notebook computers is feasible and results in a practicable way to provide positional information to a surgeon intraoperatively. MATERIALS AND METHODS: The ARTMA Virtual Patient System has been implemented on a Macintosh PowerBook G3 and, in connection with the Polhemus FASTRAK digitizer, provides intraoperative positional information during endoscopic endonasal surgery. RESULTS: Satisfactory intraoperative navigation has been realized in two- and three-dimensional medical image data sets (i.e., X-ray, ultrasound images, CT, and MR) and live video. CONCLUSIONS: This proof-of-concept study demonstrates that acceptable ergonomics and excellent performance of the system can be achieved with contemporary high-end notebook computers.

[Telenavigation and expert consultation using a stereotaxic surgical videoserver]. / 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.

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.

3D image-guided surgery on the example of the 5,300-year-old Innsbruck Iceman.

Interventional Video Tomography (IVT) is regularly used for computer-assisted 3D navigation in ear-, nose, throat, and head & neck surgery in our clinic. We present the technology and its application to collect biopsies of a 5,300 year old, completely conserved male cadaver, the Iceman. IVT links intraoperative live video with medical imaging data sets, realizing real-time surgical guidance in the live video and/or in the medical images. The IVT data contain the video images and the spatial sensor information; this has a large potential for documentation, training, teaching, and telepresence. IVT allowed us to sample the Iceman's mucosa by the minimally invasive endoscopic approach of the maxillary sinus, the nasal cavity, and the larynx, minimizing tissue damage. Visual inspection of the sinuses and the mucosa revealed the typical mucosa of a fresh cadaver, albeit originating from the stone-age.

Otorhinolaryngologic computer-assisted biopsies of the Iceman.

BACKGROUND: The Iceman is a prehistoric, completely preserved, 5300-year-old male human mummy. OBJECTIVE: To obtain the first biopsy specimens from inside the Iceman while meeting an extended standard of hygiene and following precise intraoperative guidance to the site of biopsy and keeping tissue damage to a minimum. DESIGN: Biopsy specimens from the nose, the maxillary sinus, and the larynx of the Iceman were obtained. Special caution had to be taken while performing the biopsies to not contaminate the Iceman with heavy metals or remnants of microorganisms. SUBJECT: The Iceman, a cadaver kept frozen in a glacier for 5300 years. The Iceman is in an excellent state of preservation and will allow fundamental histological, morphological, and molecular genetic insights into early man. INTERVENTION: The biopsies were planned and executed with the aid of Interventional Video Tomography, a system that guides the surgeon to the target area by combining live video with existing imaging modalities. The system does not need mechanical fixation of the subject (the Iceman) and is barely in physical contact with the subject; thus, it was the ideal tool for guiding the surgeon to the site of the biopsy samplings through a tiny canal into the nose, the maxillary sinus, and the larynx of the Iceman. RESULTS: We have obtained a number of tissue samples by precisely guided 3-dimensional navigation. Unnecessary tissue damage was avoided. CONCLUSIONS: Visual inspection of the extracted mucosa showed typical human cadaver tissue, despite its age, without clinical abnormalities. Currently, the samples are being investigated by various international scientific groups.

[3D computer-assisted ENT biopsies of the Iceman]. / 3D-computerunterstützte HNO-Biopsien des Eismannes.

The University of Innsbruck possesses a unique prehistoric, completely conserved 5300-year-old human cadaver. We report our experiences during which ENT specialists collected samples from various cavities inside the Iceman. Guidance of biopsy instruments was accomplished with computer-assisted navigation based on Interventional Video Tomography. This technology allows surgical guidance by interlinking currently available imaging modalities with live endoscopic video. The system operates without patient fixation and is practically free of external contact. Apart from sterility, special precautionary measures were necessary to avoid contamination with heavy metals or microorganisms. Visual inspection of the samples of mucosa from the nose, maxillary sinus and larynx revealed the typical patterns of a human cadaver without overt pathology.

Bacterial ghosts as multifunctional vaccine particles.

Expression of cloned PhiX174 gene E in Gram-negative bacteria results in lysis of the bacteria by formation of an E-specific transmembrane tunnel structure built through the cell envelope complex. Bacterial ghosts have been produced from a variety of bacteria including Escherichia coli. Salmonella typhimurium, Salmonella enteritidis, Vibrio cholerae, Klebsiella pneumoniae, Actinobacillus pleuropneumoniae, Haemophilus influenzae, Pasteurella haemolytica, Pasteurella multocida, and Helicobacter pylori. Such ghosts are used as non-living candidate vaccines and represent an alternative to heat or chemically inactivated bacteria. In recombinant ghosts, foreign proteins can be inserted into the inner membrane prior to E-mediated lysis via specific N-, or C-, or N- and C-terminal anchor sequences. The export of proteins into the periplasmic space or the expression of recombinant S-layer proteins vastly extents the capacity of ghosts or recombinant ghosts as carriers of foreign epitopes or proteins. Oral, aerogenic or parenteral applications of (recombinant) ghosts in experimental animals induced specific humoral and cellular immune responses against bacterial and target components including protective mucosal immunity. The most relevant advantage of ghosts and recombinant bacterial ghosts as immunogens is that no inactivation procedures that denature relevant immunogenic determinants are employed in the production of ghosts used as vaccines or as carriers of relevant antigens. The inserted target antigens into the inner membrane or into S-layer proteins are not limited in size.

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 surgeon's 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.

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.