title: Electromagnetic tracking for US-guided interventions: standardized assessment of a new compact field generator.
abstract: OBJECTIVE
  One of the main challenges related to electromagnetic tracking in the clinical setting is a placement of the field generator (FG) that optimizes the reliability and accuracy of sensor localization. Recently, a new mobile FG for the NDI Aurora(®) tracking system has been presented. This Compact FG is the first FG that can be attached directly to an ultrasound (US) probe. The purpose of this study was to assess the precision and accuracy of the Compact FG in the presence of nearby mounted US probes.
  
  
  METHODS
  Six different US probes were mounted onto the Compact FG by means of a custom-designed mounting adapter. To assess precision and accuracy of the Compact FG, we employed a standardized assessment protocol. Utilizing a specifically manufactured plate, we measured positional data on three levels of distances from the FG as well as rotational data.
  
  
  RESULTS
  While some probes had negligible influence on tracking accuracy two probes increased the mean distance error up to 1.5 mm compared with a reference measurement of 0.5 mm. The jitter error consistently stayed below 0.2 mm in all cases. The mean relative error in orientation was found to be smaller than 3°.
  
  
  CONCLUSIONS
  Attachment of an US probe to the Compact FG does not have a critical influence on tracking accuracy in most cases. Clinical benefit of this promising mobile FG must be shown in future studies.
authors.affiliation: German Cancer Research Center (DKFZ), ImNeuenheimer Feld 280, 69120, Heidelberg, Germany. a.franz@dkfz-heidelberg.de
authors.forename: A M
authors.initials: AM
authors.lastname: Franz
authors.forename: K
authors.initials: K
authors.lastname: März
authors.forename: J
authors.initials: J
authors.lastname: Hummel
authors.forename: W
authors.initials: W
authors.lastname: Birkfellner
authors.forename: R
authors.initials: R
authors.lastname: Bendl
authors.forename: S
authors.initials: S
authors.lastname: Delorme
authors.forename: H-P
authors.initials: HP
authors.lastname: Schlemmer
authors.forename: H-P
authors.initials: HP
authors.lastname: Meinzer
authors.forename: L
authors.initials: L
authors.lastname: Maier-Hein
mesh_terms: D055590:Electromagnetic Phenomena; D004867:Equipment Design; D015203:Reproducibility of Results; D018084:Ultrasonography, Interventional / Q000295:instrumentation*