Design and application of an assessment protocol for electromagnetic tracking systems

Area of Science:

• Medical instrumentation
• Electromagnetic tracking systems
• Surgical navigation

Background:

• Accurate electromagnetic tracking is crucial for minimally invasive surgery and image-guided interventions.
• Existing evaluation methods lack standardization, hindering direct comparison between different tracking systems.
• The influence of environmental factors, particularly metallic objects, on tracking accuracy requires detailed investigation.

Purpose of the Study:

• To develop and validate a novel phantom and protocol for the competitive and quantified evaluation of electromagnetic tracking systems.
• To assess the reproducibility and comparability of tracking system performance in a controlled environment.
• To investigate the impact of metallic interference on the accuracy of position and orientation measurements.

Main Methods:

• A custom-designed base plate with a precise grid of holes for position and rotation measurements was manufactured.
• Sensors were mounted on a fixture that fit into the base plate's grid holes for standardized placement.
• Relative positional and orientational errors were calculated by comparing measured values to known distances and rotations.
• The effect of metallic objects (steel, aluminum, bronze rods) on tracking accuracy was systematically evaluated.

Main Results:

• Positional jitter was measured at 0.14 mm for NDI Aurora (A) and 0.08 mm for Ascension microBIRD (B).
• Relative positional errors at 50 mm distance were 0.96±0.68 mm (A) and 1.14±0.78 mm (B).
• Relative rotation errors were 0.51° (A) and 0.04° (B), indicating NDI Aurora's lower orientation accuracy.
• Steel 416 caused the most significant distortion (up to 4.2 mm error), with Ascension microBIRD (B) being more sensitive to metallic objects.
• Ascension microBIRD (B) exhibited a systematic error in distance calculations.

Conclusions:

• The developed phantom and protocol provide a reliable method for evaluating and comparing electromagnetic tracking systems.
• NDI Aurora demonstrates superior orientation accuracy, while Ascension microBIRD shows higher sensitivity to metallic interference and systematic distance errors.
• The findings highlight the importance of considering environmental factors, especially metallic objects, when selecting and implementing electromagnetic tracking solutions.