title: A simple sensor calibration technique for estimating the 3D pose of endoscopic instruments.
abstract: BACKGROUND
  The aim of this study was to describe a simple and easy-to-use calibration method that is able to estimate the pose (tip position and orientation) of a rigid endoscopic instrument with respect to an electromagnetic tracking device attached to the handle.
  
  
  METHODS
  A two-step calibration protocol was developed. First, the orientation of the instrument shaft is derived by performing a 360° rotation of the instrument around its shaft using a firmly positioned surgical trocar. Second, the 3D position of the instrument tip is obtained by allowing the tip to come in contact with a planar surface.
  
  
  RESULTS
  The results indicate submillimeter accuracy in the estimation of the tooltip position, and subdegree accuracy in the estimation of the shaft orientation, both with respect to a known reference frame. The assets of the proposed method are also highlighted by illustrating an indicative application in the field of augmented reality simulation.
  
  
  CONCLUSIONS
  The proposed method is simple, inexpensive, does not require employment of special calibration frames, and has potential applications not only in training systems but also in the operating room.
authors.affiliation: Medical Physics Laboratory Simulation Centre, School of Medicine, University of Athens, Mikras Asias St. 75, 11527, Athens, Greece. vlahanas@med.uoa.gr.
authors.forename: Vasileios
authors.initials: V
authors.lastname: Lahanas
authors.affiliation: Medical Physics Laboratory Simulation Centre, School of Medicine, University of Athens, Mikras Asias St. 75, 11527, Athens, Greece.
authors.forename: Constantinos
authors.initials: C
authors.lastname: Loukas
authors.affiliation: Medical Physics Laboratory Simulation Centre, School of Medicine, University of Athens, Mikras Asias St. 75, 11527, Athens, Greece.
authors.forename: Evangelos
authors.initials: E
authors.lastname: Georgiou
mesh_terms: D002138:Calibration; D055590:Electromagnetic Phenomena; D006801:Humans; D020706:Laparoscopes
keywords: Instrument tracking; Laparoscopic simulation; Sensor calibration; Surgical assessment