title: A software solution to dynamically reduce metallic distortions of electromagnetic tracking systems for image-guided surgery.
abstract: OBJECTIVE
  Electromagnetic tracking systems (EMTS) have achieved a high level of acceptance in clinical settings, e.g., to support tracking of medical instruments in image-guided interventions. However, tracking errors caused by movable metallic medical instruments and electronic devices are a critical problem which prevents the wider application of EMTS for clinical applications.
  
  
  METHODS
  We plan to introduce a method to dynamically reduce tracking errors caused by metallic objects in proximity to the magnetic sensor coil of the EMTS. We propose a method using ramp waveform excitation based on modeling the conductive distorter as a resistance-inductance circuit. Additionally, a fast data acquisition method is presented to speed up the refresh rate.
  
  
  RESULTS
  With the current approach, the sensor's positioning mean error is estimated to be 3.4, 1.3 and 0.7 mm, corresponding to a distance between the sensor and center of the transmitter coils' array of up to 200, 150 and 100 mm, respectively. The sensor pose error caused by different medical instruments placed in proximity was reduced by the proposed method to a level lower than 0.5 mm in position and [Formula: see text] in orientation. By applying the newly developed fast data acquisition method, we achieved a system refresh rate up to approximately 12.7 frames per second.
  
  
  CONCLUSIONS
  Our software-based approach can be integrated into existing medical EMTS seamlessly with no change in hardware. It improves the tracking accuracy of clinical EMTS when there is a metallic object placed near the sensor coil and has the potential to improve the safety and outcome of image-guided interventions.
authors.affiliation: Chair for Medical Telematics and Medical Technology, Institute of Medical Technology, Otto-von Guericke Universität Magdeburg, G09-324, Universitätsplatz 2, 39016, Magdeburg, Germany. Mengfei.li@ovgu.de.|Research Group of Computer-Assisted Surgery, Institute of Simulation and Graphics, Otto-von-Guericke Universität Magdeburg, G29-209, Universitätsplatz 2, 39016, Magdeburg, Germany. Mengfei.li@ovgu.de.
authors.forename: Mengfei
authors.identifier: http://orcid.org/0000-0002-5653-3725
authors.initials: M
authors.lastname: Li
authors.affiliation: Research Group of Computer-Assisted Surgery, Institute of Simulation and Graphics, Otto-von-Guericke Universität Magdeburg, G29-209, Universitätsplatz 2, 39016, Magdeburg, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Hansen
authors.affiliation: Chair for Medical Telematics and Medical Technology, Institute of Medical Technology, Otto-von Guericke Universität Magdeburg, G09-324, Universitätsplatz 2, 39016, Magdeburg, Germany.
authors.forename: Georg
authors.initials: G
authors.lastname: Rose
mesh_terms: D055590:Electromagnetic Phenomena; D006801:Humans; D012984:Software; D025321:Surgery, Computer-Assisted / Q000295:instrumentation* / Q000379:methods
keywords: Clinical navigation systems; Electromagnetic tracking; Error reduction; Image-guided interventions; Metallic distortion