ever, to avoid negative postoperative surprises caused by faulty intraoperative judgments, and this problem has sparked a desire among surgeons for improved methods of intraoperative visualization. Recent de- velopments in 3D sectional imaging technology such as volume tomography and C-arm techniques from traumatology may provide simpler and more practi- cal options for intraoperative use. These new devel- opments involve less radiation exposure and are con- siderably more cost-effective than conventional CT.
The intraoperative use of CT or MRI is associated with high staffing and equipment costs. These modalities hamper the clinical course and may inter- fere with certain operating room procedures, pre- cluding several interventions. Intraoperative CT also subjects the patient to extra radiation exposure, mak- ing it inappropriate for routine operative use.
Intraoperative navigation is free of these disad- vantages. It enables the surgeon to correlate the anatomy of the operative site with the data set ac- quired before the operation. This makes it possible to locate anatomical and pathological structures with- out having to rely on subjective assessments and in- terpretations of image data sets. When we supple- ment preoperative analysis with the ability to plan surgical access routes and mark tumor boundaries and surgical clearance margins, we have a new treat- ment modality known as computer-assisted surgery.
Unlike robotic techniques, the operation is con- ducted without the use of manipulators or of semi- or fully automatic cutting, burring, or drilling instru- ments.
Surgical procedures in the head and neck region re- quire a detailed knowledge of head and neck anato- my. Particularly in the skull, structures of major func- tional and aesthetic importance are spaced close to- gether within a relatively confined area. Anatomical changes due to tumor growth, trauma-related defects or displacements, and craniofacial deformities and dysgnathias present special challenges for the sur- geon. Besides the clinical examination, which is still of fundamental importance, imaging procedures are used in the preoperative assessment of anatomical changes. Imaging studies enable us to analyze the pathological condition and plan the operation ac- cordingly. Two-dimensional techniques such as con- ventional radiography are seriously limited due to the presence of superimposed structures. Computed tomography (CT) was the first imaging modality to provide a three-dimensional (3D) representation of the clinical situation. Recent developments in 3D shadowing software can produce high-contrast sim- ulated 3D models of the skull that are particularly useful in traumatology. Once an image data set has been acquired, it can be digitally processed without further radiation exposure to provide detailed views of the bones and soft tissues. Magnetic resonance im- aging (MRI) may offer similar advantages, depending on the nature of the investigation.
These examination techniques also have major importance as postoperative studies. They provide an objective, detailed basis for evaluating the results of operative procedures, planning adjuvant therapies, and conducting follow-ups. There is still a need, how-
Introduction
Chapter 1 1
