Electromagnetic tracking in surgical and interventional environments: usability study

  • Elodie Lugez
  • Hossein Sadjadi
  • David R. Pichora
  • Randy E. Ellis
  • Selim G. Akl
  • Gabor Fichtinger
Original Article



Electromagnetic (EM) tracking of instruments within a clinical setting is notorious for fluctuating measurement performance. Position location measurement uncertainty of an EM system was characterized in various environments, including control, clinical, cone beam computed tomography (CBCT), and CT scanner environments. Static and dynamic effects of CBCT and CT scanning on EM tracking were evaluated.


   Two guidance devices were designed to solely translate or rotate the sensor in a non-interfering fit to decouple pose-dependent tracking uncertainties. These devices were mounted on a base to allow consistent and repeatable tests when changing environments. Using this method, position and orientation measurement accuracies, precision, and 95 % confidence intervals were assessed.


   The tracking performance varied significantly as a function of the environment—especially within the CBCT and CT scanners—and sensor pose. In fact, at a fixed sensor position in the clinical environment, the measurement error varied from 0.2 to 2.2 mm depending on sensor orientations. Improved accuracies were observed along the vertical axis of the field generator. Calibration of the measurements improved tracking performance in the CT environment by 50–85 %.


   EM tracking can provide effective assistance to surgeons or interventional radiologists during procedures performed in a clinical or CBCT environment. Applications in the CT scanner demand precalibration to provide acceptable performance.


Surgical navigation Electromagnetic tracking Accuracy analysis Image-guided therapy Usability study 



The authors would like to thank Dr. Abdulaziz Al Qahtani, clinical fellow, for his assistance in collecting data. This work was supported by the Natural Sciences and Engineering Research Council of Canada, and the Canada Foundation for Innovation. Gabor Fichtinger was supported as Cancer Care Ontario Research Chair.

Conflict of interest

Elodie Lugez, Hossein Sadjadi, David Pichora, Randy Ellis, and Gabor Fichtinger declare that they have no conflict of interest.


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Copyright information

© CARS 2014

Authors and Affiliations

  • Elodie Lugez
    • 1
  • Hossein Sadjadi
    • 1
  • David R. Pichora
    • 3
  • Randy E. Ellis
    • 2
  • Selim G. Akl
    • 2
  • Gabor Fichtinger
    • 1
  1. 1.Laboratory for Percutaneous Surgery, School of ComputingQueen’s UniversityKingstonCanada
  2. 2.School of ComputingQueen’s UniversityKingstonCanada
  3. 3.Departments of Surgery and Mechanical and Materials EngineeringQueen’s UniversityKingstonCanada

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