Wolfgang Freysinger

Computer‐Aided Surgery in the Petrous Bone

Objectives: We demonstrate that computer‐assisted frameless stereotactic navigation with the ISG/ELEKTA Viewing Wand system in the petrous bone is routinely possible with sufficient application accuracy.

Three-Dimensional Image-Guided Endonasal Surgery With a Microdebrider

We report the first intraoperative use of a microdebrider as a stereotactic three‐dimensional (3D) navigation instrument in paranasal and frontobasal surgery. The microdebrider uses rotating blades and an integrated suction device for controlled removal of tissue under video‐endoscopic view. The ISG Viewing Wand uses the patients computed tomography/magnetic resonance (CT/MR) data and a 3D reconstruction thereof and a highprecision position‐sensitive mechanical arm for intraoperative three‐dimensional navigation. We have linked the microdebrider to the Viewing Wand to transform it into a continuously available intraoperative stereotactic localizing device. We discuss the problems related to this extension of the Viewing Wand and demonstrate the practical use in an exemplary polypectomy.

VBH Head Holder to Improve Frameless Stereotactic Brachytherapy of Cranial Tumors

Precise target localization is essential for brachytherapy. We have adapted the VBH (Vogele-Bale-Hohner) head holder (Wellhoefer Dosimetry, Schwarzenbruck, Germany), originally developed at the University of Innsbruck, for frameless stereotactic surgery, for use in brachytherapy of cranial tumors. The VBH head holder allows for rigid, noninvasive head fixation by means of an individualized upper dental cast. Registration rods, rigidly attached to the dental cast, provide stable external points of reference. The dental cast is sucked against the upper palate by vacuum, and then the fixated patient is scanned. During simulation, the targeting device can be positioned with respect to the virtual patient using the ISG Viewing Wand. Following simulation, the real patient is repositioned under vacuum control, the targeting device repositioned as well, and the actual brachytherapy initiated. The VBH head holder is well tolerated by patients and simple to use, and various studies have confirmed submillimeter accuracy. The modified head holder in combination with a new targeting device allows for precise and well-planned insertion of hollow needles into a tumor using frameless stereotactic systems as well as being compatible for uses in other fields.

3D anatomo-radiological basis of endoscopic surgery of the paranasal sinuses.

Minimal invasive endoscopic operations in the paranasal sinuses rely on the detailed knowledge of the individual anatomy, in particular the relationship of the sinus system to neighbouring delicate and vulnerable anatomical structures. Digital CT and MR images are used for 3D reconstruction of the operating field, providing the basis for most 3D navigation systems, guiding the surgeon in close vicinity to delicate structures and so minimising the risk of iatrogenic trauma. We report the application of the ISG Viewing Wand, a computer-assisted navigation system, in endoscopic endonasal surgery related to the anatomy of the paranasal sinuses.

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 Icemans 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.

3D anatomo-radiological basis of endoscopic surgery of the paranasal sinuses@@@Bases anatomo-radiologiques en trois dimensions de la chirurgie endoscopique des sinus paranasaux

SummaryMinimal invasive endoscopic operations in the paranasal sinuses rely on the detailed knowledge of the individual anatomy, in particular the relationship of the sinus system to neigh-bouring delicate and vulnerable anatomical structures. Digital CT and MR images are used for 3D reconstruction of the operating field, providing the basis for most 3D navigation systems, guiding the surgeon in close vicinity to delicate structures and so minimising the risk of iatrogenic trauma. We report the application of the ISG Viewing Wand, a computer-assisted navigation system, in endoscopic endonasal surgery related to the anatomy of the paranasal sinuses.RésuméLes interventions menées sous endoscopie sur les sinus paranasaux nécessitent une connaissance détaillée de lanatomie individuelle, en particulier celle des rapports de ces sinus avec les structures anatomiques environnantes, fragiles et vulnérables. Les images digitalisées issues de tomographies computérisées (TDM) et dimagerie par résonance magnétique (IRM) sont utilisées pour la reconstruction en trois dimensions (3D) du champ opératoire, fournissant la base de la plupart des systèmes de navigation 3D, pour guider le chirurgien au voisinage immédiate de structures fragiles et minimiser ainsi le risque de lésions iatrogèniques. Nous rapportons lapplication du système de navigation assisté par ordinateur ISG Viewing Wand dans la chirurgie endoscopique endonasale, en rapport avec lanatomie des sinus paranasaux.

Is the Trachea a Marker of the Type of Environmental Pollution

Objectives/Hypothesis The differentiated character of changes in the mucous relief of the trachea as induced by air containing pollutants from the wastes of nickel‐, mercury‐, and cement‐producing plants and by Candida albicans occurring in the waste disposal site of a large town are identified. The trachea was chosen because it is the entrance gate for the penetration of polluted air into the lungs. Changes on the trachea influence the character and extent of changes in lungs.

Interactive telepresence and augmented reality in ENT surgery: interventional video tomography

Telepresence is surgery is a demanding technological challenge for communication tools, hard- and software. Interventional Video Tomography (IVT) [1] allows remote-guided intraoperative navigation, guidance, orientation. Provided that the partners have their copy of the medical images and a sufficient bandwidth video transmission line the IVT data set allows to share stereotactic information, like access paths or structures to avoid, by exchanging the positional and orientational information of the used sensors on the “soundtrack” of the transmitted video. Both the remote and the local partner share a file with the stereotactic information of tracked objects and may modify its contents so that an interactive, optimized remote planning of the surgery becomes possible.

Computer-Assisted Interstitial Brachytherapy

We present the current state-of-the art of computer-assisted interstitial (fractionated) brachytherapy as a “picture-book” without wanting to give an in-depth presentation of either brachytherapy itself or of otolaryngologic aspects of oncologic treatment. However, our results show that 3D-computer-assisled navigation techniques can successfully be applied in interstitial brachytherapy to exactly plan the hollow-needle’s position(s) in order to reach a prospective planning of brachytherapy which exploits the full 3D-information of the modern imagery and incorporates state-of-the-art navigational techniques.

A Passive-Marker-Based Optical System for Computer-Aided Surgery in Otorhinolaryngology: Development and First Clinical Experiences

The article by Klimek and coworkers (1999;109: 1509–1515) describes a useful application and new development in the field of computer-aided surgery in otorhinolaryngology. They have solved the problem of ubiquitous cables in the operating field, when computer assistance, three-dimensional computer-guided intraoperative navigation is used. In the course of reading the article, my attention was drawn to two aspects that deserve discussion in public and which will be addressed. When the authors check the quality of the patient-toimage registration, they state that the up to five markers that were used for checking registration between the patient and his three-dimensional–computed tomography data set are touched, and the possible deviation between the actual and the calculated position of the probe, respectively, are compared. This is, to a certain degree, not good enough as a check of registration: the markers serve as a base for the fitting routine (typically a rigid body transformation) which links the patient (i.e., the markers) to the three-dimensional data set (computed tomography or magnetic resonance), i.e., the localized marker structures in said data sets. This procedure, however, is subject to certain limitations: the markers may have changed their location between the time of radiologic imaging and surgery. This will be detected easily. If, however, the minimum of required points (viz. three) for the referencing procedure is used, then the implemented algorithm may allow “tilting” of the three-dimensional data set to provide the “optimal” patient-to-image registration. If this happens, and if only the marker structures are touched for evaluation purposes, then the system will seem to work correctly. However, if only the markers are located correctly in the relevant anatomic area the system is not providing correct positions. In the course of intraoperative use of the navigational system, erroneous position detection will result thereof. To guarantee a reliable intraoperative evaluation procedure while the patient has not been washed and sterilely draped, we would like to draw attention to a recent paper in which a suitable procedure was proposed. When using a Vogele-Bale-Hohner (VBH) mouthpiece for patient referencing and intraoperative fixation, we would like to mention that we are achieving excellent intraoperative results with such a device. This has been shown in detail by Bale, Vogele, and others. Moreover, the repositioning accuracy of this device has been found to be submillimetric and as such can provide an excellent means for both preoperative and intraoperative patientto-image registration. This is true, if registration rods, as provided by the manufacturer of the VBH mouthpiece (Medical Intelligence, Schwabmünchen, Germany), are used. In combination with a properly chosen underpressure to affix the device to the upper dentition of the patient, excellent results can be achieved, which even allow the use of this device for computer-assisted microsurgery in the petrous bone. In the case of edentulous patients, suboptimal repositioning accuracy might occur. In combination with a proper non-invasive head fixation technology, however, sufficient intraoperative patient-to-image registration and patient immobilization will be attainable. Eventually, use of mouthpieces will result in accelerated setup and registration time for intraoperative navigation systems as patient-to-image registration will be possible in the preoperative phase.