Virtual reality in endonasal surgery.

Virtual environments provide a new dimension of graphic simulation. The interaction between the human and the computer is now intuitive for the user. The use of virtual reality (VR) gives the user the feeling of participating in a (computer generated) scenario very much like reality. This feeling is an essential requirement for simulation of surgical interventions using digital data. Especially in the fields of sinus and skull-base surgery, computer assisted simulation could present a valuable and effective alternative method for honing endoscopic skills. Traditionally, surgeons gain experience through anatomic preparation and education by more experienced colleagues. Landmarks like skull base, carotid arteria or optical nerve have to be identified intraoperatively in order to orientate in this critical region. Highly sensitive structures can be damaged most easily. The quality of surgical skills can be characterized as the sum of knowledge, individual experience and manual dexterity. It is conceivable that a surgeon's level of training and experience could be significantly increased by use of VR. With this in mind, a VR-based simulator for procedures in sinus surgery will improve most of these parts. To provide the virtual environment, a realistic representation of the region of interest with all relevant anatomical structures is required. Based on data from tomographic imaging studies, a three-dimensional representation of the paranasal sinuses is semiautomatically reconstructed. Textures derived from endoscopic images are superimposed on the virtual anatomic structures and provide better realism. Two main components of the VR interface can be distinguished: the 3-D interaction to guide the surgical instruments and the 2-D graphical user interface for visual feedback and control of the session. Moreover, the 3-D interaction has to be realized by means of Virtual Reality techniques providing a simulation of an endoscope and an intuitive handling of other surgical instruments.