Computer-assisted image-guided surgery in pediatric skull-base procedures.

Skull-base surgery is characterized by the variety of important neural and vascular structures within a narrow operating field. Although preoperative imaging by computed tomography (CT) and magnetic resonance imaging (MRI) and the use of microsurgical techniques have improved intraoperative orientation, a large number of complications still are caused by localization problems. Especially in pediatric skull-base surgery, maximum localization accuracy during surgery is required. The authors developed a localizing system based on tomographic imaging (such as CT or MRI) to achieve safer surgery by providing highly accurate location information. The preliminary successful experience in the use of the Aachen computer-assisted surgery device for pediatric skull-base surgery (14 cases) is presented. Indication include juvenile angiofibroma of the nasopharynx, infectious and tumorous diseases of the paranasal sinuses, orbital tumors, foreign bodies, and intracranial abscess formation.

[Extraction of orbital foreign bodies using a new kind of image processing system]. / Extraktion von orbitalen Fremdkörpern mit Hilfe eines neuartigen Bildverarbeitungssystems.

We present a new localization system in orbital surgery. The procedure is based on the linkage of two methods. A preoperative thin-layer CT scan is taken and the image data are fed into a high-capacity computer which computes a three-dimensional model of the orbit. Intraoperatively, the volume model of the skull is linked to a mechanical arm for position measurement. Surgical instruments can be mounted to this arm. The computer then projects the position of the instrument into the volume model of the orbit, so that the surgeon can follow the movements of his instruments on the monitor. The surgeon has a means of checking position that comes close to constant intraoperative CT monitoring. Thereby the surgeon is able to localize even small foreign bodies without extensive explorations. We present six patients in whom orbital foreign bodies had to be extracted during the past 5 years. A 44-year-old man had an iron foreign body; the external wound was treated surgically elsewhere. Two patients (25 and 22 years old) had glass foreign bodies; in one of them the splinters were not seen using conventional X-ray. Choosing the exact level with the Hounsfield window, the foreign bodies could be demonstrated on the monitor. In three patients with orbital fractures and compression of the optic nerve, dislocated bone splinters were extracted. The localization of those splinters was easy using the imaging system, but would have been rather difficult by other means.(ABSTRACT TRUNCATED AT 250 WORDS)

[Artificial intelligence methods for support of medial patient education before surgical interventions in the region of the neck-nose-ear]. / Methoden künstlicher Intelligenz zur Unterstützung bei der ärztlichen Aufklärung vor operativen Eingriffen im Hals-Nasen-Ohrenbereich.

As a rule, curative operations require the patient's consent. Determined by the expansion of surgical possibilities, the kind and frequency of specific complications are subjected to constant changes. The physician is encouraged to explain therapeutic methods as well as the probability of complications within the patient's grasp. It has been investigated to what extent methods of artificial intelligence (AI) are suited for assisting the physician in this task. For this purpose, a comprehensive list of surgical complications as reported in research literature has been compiled. The list has been transferred into a hierarchical structure which can be depicted as a rule tree classified according to topographic aspects. In each otolaryngological operation, the reported complications can be classed with these rules. By employing an expert system (Fig. 1), the physician is capable of compiling an individualized document of agreement (Fig. 2) which serves as a basis for the explanatory talk with the patient.

Surgical decompression in endocrine orbitopathy--a three-dimensional locating device ensures greater safety.

Numerous techniques have been described for surgical decompression in endocrine orbitopathy. Irrespective of the approach chosen, the procedure might involve hazards to important vessels and nerves near the base of the skull. When the optic nerve is compressed and relief of pressure at the orbital apex is necessary, the internal carotid artery and the cavernous sinus are at risk as well as the optic nerve itself. Although the use of modern optical instruments such as operating microscopes and endoscopes is now standard practice for this form of surgery, adequate topographical orientation is not achieved in every case. For this reason a computer-assisted locating device developed in this department has been employed by us in 7 cases of endocrine orbitopathy where surgical decompression was required. By using computer-tomographic or MR-tomographic image data, the positions of structures at risk can be plotted to within 0.6 mm. Used in conjunction with an operating microscope and with endoscopic techniques, the system proved helpful in all cases.

[Computer-assisted placement for after-loading procedures with iridium 192]. / Computerunterstützte Positionierung für das Nachladeverfahren mit Iridium-192.

Extremely high precision is needed to place radiation sources in the after-loading technique, but localisation techniques so far described do not offer the required accuracy. We used the computer-assisted surgery (CAS) localising system for the placement of after-loading probes in patients with head and neck carcinoma. Surgical instruments can be positioned without visual control using the CAS system. Since 1989 after-loading tubes have been placed using the CAS method. We evaluated the accuracy to be better than 1 mm. Ten after-loading treatments with iridium 192 of head and neck carcinomas were carried out between August 1989 and February 1991 with exact placement of the after-loading tubes in the nasopharynx. It seems feasible to treat cerebral tumours as well as tumours of the pelvic region by computer-assisted after-loading brachytherapy.

Image- and model-based surgical planning in otolaryngology.

Preoperative evaluation of any operating field is essential for the preparation of surgical procedures. The relationship between pathology and adjacent structures, and anatomically dangerous sites need to be analyzed for the determination of intraoperative action. For the simulation of surgery using three-dimensional imaging or individually manufactured plastic patient models, the authors have worked out different procedures. A total of 481 surgical interventions in the maxillofacial region, paranasal sinuses, orbit, and the anterior and middle skull base, in addition to neurotologic procedures were presurgically simulated using three-dimensional imaging and image manipulation. An intraoperative simulation device, part of the Aachen Computer-Assisted Surgery System, had been applied in 407 of these cases. In seven patients, stereolithography was used to create plastic patient models for the preparation of reconstructive surgery and prostheses fabrication. The disadvantages of this process include time and cost; however, the advantages included (1) a better understanding of the anatomic relationships, (2) the feasibility of presurgical simulation of the prevailing procedure, (3) an improved intraoperative localization accuracy, (4) prostheses fabrication in reconstructive procedures with an approach to more accuracy, (5) permanent recordings for future requirements or reconstructions, and (6) improved residency education.

[Decompression of the optic nerve after fractures of the rhino-basal skull with computer-assisted surgery]. / Dekompression des Nervus opticus nach Frakturen des Riechschädels mit Hilfe von CAS (Computer Assisted Surgery).

Referring to 22 cases of surgery after frontobasal fractures of different origin with loss of vision, the surgical procedure is discussed with special consideration of the approach, technique and timing of the operation. We conclude that the external rhinological approach through the ethmoid sinus is the best and easiest access in cases of loss of vision with verified fracture or haematoma. A number of patients were operated using CAS (Computer Assisted Surgery)-Systems, a CT-based tool for three-dimensional orientation. It proved to be very useful for the surgeon, saving time and reducing the risk of additional damage. According to our experience and the results of other authors we believe that surgical intervention should be performed as early as possible.

[Identification and removal of orbital foreign bodies using the CAS (Computer-Assisted-Surgery) system]. / Identifikation und Entfernung orbitaler Fremdkörper mit dem CAS-(Computer-Assisted-Surgery) System.

Identification and extraction of orbital foreign bodies can cause problems in special cases. Small, retroocular localized fragments can be hard to detect, severe bleeding and traumatically damaged anatomy can render orientation difficult. At the Department of Otolaryngology, Plastic Head and Neck Surgery of Aachen University Hospital we used the investigational new CAS (Computer-Assisted-Surgery) device in several such cases with good success. CAS is a new localizing technique designed to assist the head and neck surgeon during surgery providing real-time position information. The method is based upon a three dimensional volume model of the patient's skull generated by preceding computed tomography imaging procedures such as CT or MRI scan. Intraoperative correlation of 3D-model and the patient's skull allows for real-time position display of a surgical instrument on the monitor screen. Accuracy of the method has been experimentally determined to be within 1 mm. Thereby the surgeon is able to localize even small foreign bodies without extensive exploration. In the case of multiple foreign bodies the surgeon gets a simple documentation facility, which of the visible fragments have already been extracted. Medially placed foreign bodies could be removed via an endonasal approach. Encouraged by these results we recommend CAS for the extraction of orbital foreign bodies.

Endoscopic surgery of the rhinobasis with a computer-assisted localizer.

The endoscope is useful for the diagnosis and surgical therapy of diseases of the nose, the paranasal sinuses and its neighboring regions, and allows for microinvasive, functional approaches. The reduced invasiveness of therapeutic procedures is sometimes accompanied by insufficient clearness of the surgical field, however. This significant problem is solved by the computer-assisted-surgery (CAS) system, an intraoperative localizer. It allows continuous orientation based on three-dimensional reconstructed preoperative CT scans with superimposed positioning of the endoscope. We have now adapted CAS for endoscopic sinus surgery, which meant that a variety of visualization methods were tested. A conventional straightforward endoscope was used in combination with, or as, the localizing probe. A dual-display technique was adjusted to video-endoscopic procedures: the information of the localizer is displayed on one monitor while the video-endoscopic picture is viewed on a second screen. In addition, a single-display technique with both images on one monitor was developed. It proved to be the most promising way of combining endoscopy and intraoperative CT-image-guided localization.

[Interdisciplinary multi-modality therapy of advanced hypopharyngeal and proximal esophageal carcinomas]. / Interdisziplinäre multimodale Therapie fortgeschrittener hypopharynx- und proximaler Oesophaguskarzinome.

A multimodal interdisciplinary concept including an aggressive neoadjuvant radiochemotherapy and a multivisceral resection with esophagolaryngectomy and bilateral modified neck dissection was introduced for the treatment of tumors of the cervical esophagus and hypopharynx. In 75% of the patients a R0-resection was achieved resulting in a 5-year survival rate of 38.5% and good functional results. Free jejunal interposition was the most favorable reconstruction because gastric transposition was followed by an increased rate of anastomotic insufficiencies and stenoses requiring bouginage.