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

Abstract

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 (E(RMS)) 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 degrees +/- 0.14 degrees with respect to the axial and 0.91 degrees +/- 0.68 degrees 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.

Electromagnetic Tracking in Medicine—A Review of Technology, Validation, and Applications

“…Many studies assessing EM tracking systems for CAI can be found in the literature, e.g., [3,6,7,15,19,25,36,39,45,51,59,60,61,66,74,82,83,86,89,102,120,122,152,154,159,165,169,170,172,196,202,206,207]. However, in many cases, the results of these studies are not comparable because different measurement protocols and evaluation methods were used.…”

Marker-free registration for the accurate integration of CT images and the subject's anatomy during navigation surgery of the maxillary sinus

“…22 The electromagnetic navigation system has a narrower measurement region, and errors can be generated by metal instruments such as stainless steel surgical instruments. 23 Image errors are dependent upon the image modes and are related to the sensor matrix size, slice thickness, voxel size, volume acquisition, signal-to-noise ratio, contrast, background structures, image distortion and software errors. 24 MRI has problems of motion artefacts and geometric inaccuracy because it has a longer scanning time, lower resolution and contrast, and limited visibility to bone tissue than CT. Cone beam CT has a smaller scan field (only 15-20cm) than multislice CT (MSCT), and is more accurate in the central region of the image.…”

Target registration and target positioning errors in computer‐assisted neurosurgery: proposal for a standardized reporting of error assessment

“…Electromagnetic navigation may provide similar accuracy but are distorted by external magnetic fields and metal objects, leading to incorrect position sensing of up to 4 mm (71)(72)(73).…”