title: An analysis of tracking error in image-guided neurosurgery.
abstract: OBJECTIVE
  This study quantifies some of the technical and physical factors that contribute to error in image-guided interventions. Errors associated with tracking, tool calibration and registration between a physical object and its corresponding image were investigated and compared with theoretical descriptions of these errors.
  
  
  METHODS
  A precision milled linear testing apparatus was constructed to perform the measurements.
  
  
  RESULTS
  The tracking error was shown to increase in linear fashion with distance normal to the camera, and the tracking error ranged between 0.15 and 0.6 mm. The tool calibration error increased as a function of distance from the camera and the reference tool (0.2-0.8 mm). The fiducial registration error was shown to improve when more points were used up until a plateau value was reached which corresponded to the total fiducial localization error ([Formula: see text]0.8 mm). The target registration error distributions followed a [Formula: see text] distribution with the largest error and variation around fiducial points.
  
  
  CONCLUSIONS
  To minimize errors, tools should be calibrated as close as possible to the reference tool and camera, and tools should be used as close to the front edge of the camera throughout the intervention, with the camera pointed in the direction where accuracy is least needed during surgery.
authors.affiliation: McConnell Brain Imaging Centre, Montreal Neurological Institute and Hospital, McGill University, WB 221, 3801 University Street, Montreal, QC, H3A 2B4, Canada. ian.gerard@mail.mcgill.ca.
authors.forename: Ian J
authors.initials: IJ
authors.lastname: Gerard
authors.affiliation: McConnell Brain Imaging Centre, Montreal Neurological Institute and Hospital, McGill University, WB 221, 3801 University Street, Montreal, QC, H3A 2B4, Canada.
authors.forename: D Louis
authors.initials: DL
authors.lastname: Collins
mesh_terms: D002138:Calibration; D006801:Humans; D019300:Medical Errors; D019635:Neurosurgical Procedures / Q000379:methods*; D025321:Surgery, Computer-Assisted / Q000379:methods*
keywords: Calibration; Image-guided neurosurgery; Registration error; Tracking error