title: Tracking of the liver for navigation in open surgery.
abstract: OBJECTIVE
  A main task of navigation systems assisting a surgeon during an intervention is to determine the spatial position of instruments relative to the organ. In comparison to navigation of hard tissue, this is still a challenge for navigation in soft tissue. In this contribution a method is presented to measure the position and the deformation of the liver.
  
  
  METHODS
  Therefore, reflective fiducials are fixed at the surface of the liver, whose spatial positions are measured with an optical position measurement system. Therewith the position of the whole liver is calculated. The deformation at the surface of the liver is determined using a model of the surface. The method was verified in an experiment with pig liver.
  
  
  RESULTS
  The position of the liver could be tracked. Spatial deviations because of the deformation of the liver could be reduced by 36%.
  
  
  CONCLUSIONS
  This method can be applied in navigation of instruments in open liver surgery to track the position of the liver.
authors.affiliation: Micro Technology and Medical Device Engineering (MIMED), TU München, Munich, Germany. mathias.markert@tum.de
authors.forename: Mathias
authors.initials: M
authors.lastname: Markert
authors.forename: Angelika
authors.initials: A
authors.lastname: Koschany
authors.forename: Tim
authors.initials: T
authors.lastname: Lueth
mesh_terms: D004867:Equipment Design; D004869:Equipment Safety; D005260:Female; D006498:Hepatectomy / Q000295:instrumentation* / Q000379:methods; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D021621:Imaging, Three-Dimensional / Q000379:methods; D007813:Laparotomy / Q000379:methods; D008297:Male; D055096:Optical Devices; D019047:Phantoms, Imaging; D015641:Radiography, Interventional; D025321:Surgery, Computer-Assisted / Q000295:instrumentation* / Q000379:methods*; D018084:Ultrasonography, Interventional