[Evaluation of a DC pulsed magnetic tracking system in neurosurgical navigation: technique, accuracies, and influencing factors].

Navigation systems are useful instruments in cranial neurosurgery. For specification of position, so-called sensor-based navigation techniques use: (a) a signal emitter that generates a defined electromagnetic field in the area of the operation site; and (b) small sensors that detect the position of various operating instruments in the electromagnetic field. For a long time, owing to a lack of clinical data and long-term studies, electromagnetic systems have been regarded as error-prone and imprecise. With the development of a pulsed direct current (DC) technique, precision levels can now be reached that are comparable with those of established optical and mechanical measuring procedures. However, it must be noted that the influence on the measuring accuracy within the operating field increases with increasing susceptibility of the various metals used in the operating theatre (titanium<aluminium<high-alloy steels<low-alloy steels). The technique, accuracy, and influencing factors of a DC pulsed magnetic tracking system were investigated in more than 200 cases.