Evaluation of a new electromagnetic tracking system using a standardized assessment protocol

This note uses a published protocol to evaluate a newly released 6 degrees of freedom electromagnetic tracking system (Aurora, Northern Digital Inc.). A practice for performance monitoring over time is also proposed. The protocol uses a machined base plate to measure relative error in position and orientation as well as the influence of metallic objects in the operating volume. Positional jitter (ERMS) was found to be 0.17 mm ± 0.19 mm. A relative positional error of 0.25 mm ± 0.22 mm at 50 mm offsets and 0.97 mm ± 1.01 mm at 300 mm offsets was found. The mean of the relative rotation error was found to be 0.20° ± 0.14° with respect to the axial and 0.91° ± 0.68° for the longitudinal rotation. The most significant distortion caused by metallic objects is caused by 400-series stainless steel. A 9.4 mm maximum error occurred when the rod was closest to the emitter, 10 mm away. The improvement compared to older generations of the Aurora with respect to accuracy is substantial.