title: In-vitro evaluation of a soft-tissue navigation system for laparoscopic prostatectomy.
abstract: OBJECTIVE
  We introduce a custom-designed phantom model for the in-vitro evaluation of an augmented reality-based soft-tissue navigation system for ultrasound-guided prostate interventions.
  
  
  METHODS
  Transrectal ultrasound segmentation of the prostate, navigation aid placement, initial registration, endoscope tracking, and enhanced visualization steps in the navigation procedure were performed to accommodate the actual prostatic motion. In-vitro laparoscopic manipulations simulating surgical procedures were performed by a physician using human prostate specimens. The target visualization error, defining the accuracy of the tracking, is determined by means of a leave-out test strategy by alternately using four navigation aids for endoscope registration and the remaining two navigation aids for accuracy verification.
  
  
  RESULTS
  The introduction of the navigation aids lasted approximately 3 minutes. The navigation aids and especially their barbs were visible because of their ultrasound reflecting nature. For each organ, 1000 endoscope registrations were calculated, in which two randomly chosen navigation aids served the purpose of verifying the pose. We were able to demonstrate that the superimposed image could follow automatically the videoendoscopic real-time view. The mean target visualization errors for the respective trials were determined as 0.81 (±0.12) mm, 0.62 (±0.14) mm, and 0.98 (±0.23) mm.
  
  
  CONCLUSIONS
  The ultrasound-based inside-out navigation system for laparoscopic prostatectomy overcomes the problem of tissue shift and deformation in an in-vitro model. In case of organ movement, the augmented picture with the detected navigation aids could follow the videoendoscopic image using the navigation aids as landmarks.
authors: Department of Urology, SLK Kliniken Heilbronn, Heilbronn, Germany.
authors: Dogu
authors: D
authors: Teber
authors: Tobias
authors: T
authors: Simpfendörfer
authors: Selcuk
authors: S
authors: Guven
authors: Matthias
authors: M
authors: Baumhauer
authors: Ali Serdar
authors: AS
authors: Gözen
authors: Jens
authors: J
authors: Rassweiler
mesh_terms: D004724:Endoscopy; D006801:Humans; D010535:Laparoscopy; D008297:Male; D011467:Prostate / Q000000981:diagnostic imaging / Q000601:surgery*; D011468:Prostatectomy / Q000379:methods*; D025321:Surgery, Computer-Assisted / Q000379:methods*; D014463:Ultrasonography; D036761:Ultrasound, High-Intensity Focused, Transrectal / Q000379:methods*