Patent ID: 8290572

Claim:
A navigation system to compensate for distortion of an electromagnetic (EM) field caused by a tool in the EM field, comprising: a plurality of coils, wherein each of the plurality of coils is configured to generate an EM field; a tool positionable relative to a patient to assist in performing a procedure on the patient, wherein the tool includes a ferromagnetic material that distorts the EM field generated by each of the plurality of coils to form a distorted field; a tool coil positioned adjacent to at least a portion of the tool, wherein the tool coil is configured to sense the EM field generated by each of the plurality of coils and the distorted field and further configured to generate a tool coil signal based on the sensed EM field generated by each of the plurality of coils and the distorted field; a sensor coil configured to sense the EM field generated by each of the plurality of coils and the distorted field and further configured to generate a sensor coil signal based on the sensed EM field generated by each of the plurality of coils and the distorted field; and a signal processor configured to receive the tool coil signal and the sensor coil signal and further configured to determine a proper orientation and position of the sensor coil by adjusting the sensor coil signal with the tool coil signal to compensate for the distorted field.