title: Proof-of-concept of a laser mounted endoscope for touch-less navigated procedures.
abstract: OBJECTIVE
  During navigated procedures a tracked pointing device is used to define target structures in the patient to visualize its position in a registered radiologic data set. When working with endoscopes in minimal invasive procedures, the target region is often difficult to reach and changing instruments is disturbing in a challenging, crucial moment of the procedure. We developed a device for touch less navigation during navigated endoscopic procedures.
  
  
  METHODS
  A laser beam is delivered to the tip of a tracked endoscope angled to its axis. Thereby the position of the laser spot in the video-endoscopic images changes according to the distance between the tip of the endoscope and the target structure. A mathematical function is defined by a calibration process and is used to calculate the distance between the tip of the endoscope and the target. The tracked tip of the endoscope and the calculated distance is used to visualize the laser spot in the registered radiologic data set.
  
  
  RESULTS
  In comparison to the tracked instrument, the touch less target definition with the laser spot yielded in an over and above error of 0.12 mm. The overall application error in this experimental setup with a plastic head was 0.61 ± 0.97 mm (95% CI -1.3 to +2.5 mm).
  
  
  CONCLUSIONS
  Integrating a laser in an endoscope and then calculating the distance to a target structure by image processing of the video endoscopic images is accurate. This technology eliminates the need for tracked probes intraoperatively and therefore allows navigation to be integrated seamlessly in clinical routine. However, it is an additional chain link in the sequence of computer-assisted surgery thus influencing the application error.
authors.affiliation: Department of Otorhinolaryngology, Medical University Innsbruck, Innsbruck, Austria. florian.kral@i-med.ac.at
authors.forename: Florian
authors.initials: F
authors.lastname: Kral
authors.forename: Oezguer
authors.initials: O
authors.lastname: Gueler
authors.forename: Martina
authors.initials: M
authors.lastname: Perwoeg
authors.forename: Zoltan
authors.initials: Z
authors.lastname: Bardosi
authors.forename: Elisabeth J
authors.initials: EJ
authors.lastname: Puschban
authors.forename: Herbert
authors.initials: H
authors.lastname: Riechelmann
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Freysinger
mesh_terms: D019723:Endoscopes; D004867:Equipment Design; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D007091:Image Processing, Computer-Assisted; D007834:Lasers; D008953:Models, Anatomic; D015233:Models, Statistical; D044582:Neuroendoscopes; D044583:Neuroendoscopy / Q000295:instrumentation / Q000379:methods; D038361:Neuronavigation / Q000379:methods; D012886:Skull; D020535:Video-Assisted Surgery / Q000295:instrumentation* / Q000379:methods
keywords: computer assisted surgery; image processing; minimal invasive surgery; neurosurgery; sinus surgery