title: Augmented reality: a new tool to improve surgical accuracy during laparoscopic partial nephrectomy? Preliminary in vitro and in vivo results.
abstract: BACKGROUND
  Use of an augmented reality (AR)-based soft tissue navigation system in urologic laparoscopic surgery is an evolving technique.
  
  
  OBJECTIVE
  To evaluate a novel soft tissue navigation system developed to enhance the surgeon's perception and to provide decision-making guidance directly before initiation of kidney resection for laparoscopic partial nephrectomy (LPN).
  
  
  METHODS
  Custom-designed navigation aids, a mobile C-arm capable of cone-beam imaging, and a standard personal computer were used. The feasibility and reproducibility of inside-out tracking principles were evaluated in a porcine model with an artificially created intraparenchymal tumor in vitro. The same algorithm was then incorporated into clinical practice during LPN.
  
  
  METHODS
  Evaluation of a fully automated inside-out tracking system was repeated in exactly the same way for 10 different porcine renal units. Additionally, 10 patients underwent retroperitoneal LPNs under manual AR guidance by one surgeon.
  
  
  METHODS
  The navigation errors and image-acquisition times were determined in vitro. The mean operative time, time to locate the tumor, and positive surgical margin were assessed in vivo.
  
  
  CONCLUSIONS
  The system was able to navigate and superpose the virtually created images and real-time images with an error margin of only 0.5 mm, and fully automated initial image acquisition took 40 ms. The mean operative time was 165 min (range: 135-195 min), and mean time to locate the tumor was 20 min (range: 13-27 min). None of the cases required conversion to open surgery. Definitive histology revealed tumor-free margins in all 10 cases.
  
  
  CONCLUSIONS
  This novel AR tracking system proved to be functional with a reasonable margin of error and image-to-image registration time. Mounting the pre- or intraoperative imaging properties on real-time videoendoscopic images in a real-time manner will simplify and increase the precision of laparoscopic procedures.
authors.affiliation: Department of Urology, SLK-Kliniken Heilbronn, University of Heidelberg, Heidelberg, Germany.
authors.forename: Dogu
authors.initials: D
authors.lastname: Teber
authors.forename: Selcuk
authors.initials: S
authors.lastname: Guven
authors.forename: Tobias
authors.initials: T
authors.lastname: Simpfendörfer
authors.forename: Mathias
authors.initials: M
authors.lastname: Baumhauer
authors.forename: Esref Oguz
authors.initials: EO
authors.lastname: Güven
authors.forename: Faruk
authors.initials: F
authors.lastname: Yencilek
authors.forename: Ali Serdar
authors.initials: AS
authors.lastname: Gözen
authors.forename: Jens
authors.initials: J
authors.lastname: Rassweiler
mesh_terms: D000368:Aged; D000465:Algorithms; D000818:Animals; D005260:Female; D006801:Humans; D010535:Laparoscopy; D008297:Male; D008875:Middle Aged; D009392:Nephrectomy / Q000379:methods* / Q000592:standards*; D015203:Reproducibility of Results; D025321:Surgery, Computer-Assisted; D013552:Swine