Error compensation for electromagnetic navigation in dental implantology

Electromagnetic position sensing in navigation of metallic instruments requires measures for compensating for error due to distortions of the generated electromagnetic field by the metallic objects. In dental implantology, the working volume can be modelled by a plate at a defined position. Pitch, yaw and movements along the drill axis of the tool in the active working volume are small. Thus, error compensation is necessary only for three degrees of freedom for this application. We build a setup for the instrument navigation with a field generator fixed to a patient seat and performed tool calibrations in a defined working volume. During calibration, a vector field of error vectors was found and stored in a look-up table. The pose-dependant error vectors are determined at fixed supporting points and defined rotations around the drill axis of the tool. Entries of the look-up table were used to compensate for errors during navigation. Two experiments were performed, both resulting in positioning accuracy below 1 mm. Yet, robustness for clinical use of the method has to be proven.