Comparative examination of the accuracy of a mechanical and an optical system in CT and MRT based instrument navigation

The aim of an intraoperative instrument navigation system is to support the surgeon in the localization of anatomical regions and to guide the use of surgical instruments. An overview of technical principles and literature re ports on various navigation systems is provided here. The navigation accura cy (tested on a plastic phantom under simulated operating room conditions) of the mechanical Viewing Wand system and the optical SPOCS system amounts to 1 to 3 mm for computerized tomography (CT) data, with a significant inve rse dependence on the layer thickness. The values for magnetic resonance to mography (MRT) data are significantly higher. In regard to the choice of re gistration points, a statistically inverse dependence exists between the nu mber of points and the distance between the points. During the time period between autumn 1993 and mid-1999, more than 120 clinical applications were performed. The intraoperative accuracy was in the range of less than or equ al to3 mm. Registering the patient position with preoperatively inserted sc rew markers achieved accuracy values of less than or equal to2 mm. The inst rument navigation technique has proved to be very advantageous for the spat ial orientation of the surgeons. The possibility of checking resection bord ers has opened up new perspectives in tumor surgery. A quality improvement and a reduction of the operational risks as well as a considerable decline in the stress placed on the patient can be expected in the near future due the techniques of computer-assisted surgery.