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    Augmented Reality: A New Tool To Improve Surgical Accuracy during Laparoscopic Partial Nephrectomy? Preliminary In Vitro and In Vivo Results
    (ELSEVIER, 2009) Teber, Dogu; Guven, Selcuk; Simpfendoerfer, Tobias; Baumhauer, Mathias; Gueven, Esref Oguz; Yencilek, Faruk; Goezen, Ali Serdar
    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). Design, setting, and participants: 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. Interventions: 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. Measurements: 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. Results and limitations: 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: 1327 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. (C) 2009 European Association of Urology Published by Elsevier B.V. All rights reserved.
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    In-Vitro Evaluation of a Soft-Tissue Navigation System for Laparoscopic Prostatectomy
    (MARY ANN LIEBERT, INC, 2010) Teber, Dogu; Simpfendoerfer, Tobias; Güven, Selçuk; Baumhauer, Matthias; Gözen, Ali Serdar; Rassweiler, Jens
    Purpose: 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. Materials and 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.