title: Electromagnetic tracking in surgical and interventional environments: usability study.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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 %.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Laboratory for Percutaneous Surgery, School of Computing, Queen's University, Kingston, ON, K7L 3N6, Canada.
authors.forename: Elodie
authors.initials: E
authors.lastname: Lugez
authors.forename: Hossein
authors.initials: H
authors.lastname: Sadjadi
authors.forename: David R
authors.initials: DR
authors.lastname: Pichora
authors.forename: Randy E
authors.initials: RE
authors.lastname: Ellis
authors.forename: Selim G
authors.initials: SG
authors.lastname: Akl
authors.forename: Gabor
authors.initials: G
authors.lastname: Fichtinger
mesh_terms: D002138:Calibration; D054893:Cone-Beam Computed Tomography / Q000295:instrumentation*; D003952:Diagnostic Imaging / Q000295:instrumentation*; D055590:Electromagnetic Phenomena; D004867:Equipment Design; D006801:Humans; D015642:Radiology, Interventional / Q000295:instrumentation*; D025321:Surgery, Computer-Assisted / Q000295:instrumentation*