Technical accuracy of a neuronavigation system measured with a high-precision mechanical micromanipulator

OBJECTIVE: This study was designed to determine and evaluate the different system-inherent sources of erroneous target localization of a light-emitting diode (LED)-based neuronavigation system (StealthStatisn, Stealth Technologies, Boulder, CO). METHODS: The localization accuracy was estimated by applying a high-precision mechanical micromanipulator to move and exactly locate (+/-0.1 mu m) the pointer at multiple positions in the physical three-dimensional space. The localization error was evaluated by calculating the spatial distance between the (known) LED positions and the LED coordinates measured by the neuronavigator, The results are based on a study of approximately 280,000 independent coordinate measurements. RESULTS: The maximum localization error detected was 0.55 +/- 0.29 mm, with the z direction (distance to the camera array) being the most erroneous coordinate. Minimum localization error was found at a distance of 1400 mm from the central camera (optimal measurement position). Additional error due to 1) mechanical vibrations of the camera tripod (+/-0.15 mm) and the reference frame (+/-0.08 mm) and 2) extrapolation of the pointer tip position from the LED coordinates of at least +/-0.12 mm were detected, leading to a total technical error of 0.55 +/- 0.64 mm. CONCLUSIONS: Based on this technical accuracy analysis, a set of handling recommendations is proposed, leading to an improved localization accuracy. The localization error could be reduced by 0.3 +/- 0.15 mm by correct camera positioning (1400 mm distance) plus 0.15 mm by vibration-eliminating fixation of the camera. Correct handling of the probe during the operation may improve the accuracy by up to 0.1 mm.