title: Navigation system for minimally invasive esophagectomy: experimental study in a porcine model.
abstract: BACKGROUND
  Navigation systems potentially facilitate minimally invasive esophagectomy and improve patient outcome by improving intraoperative orientation, position estimation of instruments, and identification of lymph nodes and resection margins. The authors' self-developed navigation system is highly accurate in static environments. This study aimed to test the overall accuracy of the navigation system in a realistic operating room scenario and to identify the different sources of error altering accuracy.
  
  
  METHODS
  To simulate a realistic environment, a porcine model (n = 5) was used with endoscopic clips in the esophagus as navigation targets. Computed tomography imaging was followed by image segmentation and target definition with the medical imaging interaction toolkit software. Optical tracking was used for registration and localization of animals and navigation instruments. Intraoperatively, the instrument was displayed relative to segmented organs in real time. The target registration error (TRE) of the navigation system was defined as the distance between the target and the navigation instrument tip. The TRE was measured on skin targets with the animal in the 0° supine and 25° anti-Trendelenburg position and on the esophagus during laparoscopic transhiatal preparation.
  
  
  RESULTS
  On skin targets, the TRE was significantly higher in the 25° position, at 14.6 ± 2.7 mm, compared with the 0° position, at 3.2 ± 1.3 mm. The TRE on the esophagus was 11.2 ± 2.4 mm. The main source of error was soft tissue deformation caused by intraoperative positioning, pneumoperitoneum, surgical manipulation, and tissue dissection.
  
  
  CONCLUSIONS
  The navigation system obtained acceptable accuracy with a minimally invasive transhiatal approach to the esophagus in a realistic experimental model. Thus the system has the potential to improve intraoperative orientation, identification of lymph nodes and adequate resection margins, and visualization of risk structures. Compensation methods for soft tissue deformation may lead to an even more accurate navigation system in the future.
authors.affiliation: Department of General, Abdominal, and Transplant Surgery, Heidelberg University, Im Neuenheimer Feld 110, 69120, Heidelberg, Germany, felix.nickel@med.uni-heidelberg.de.
authors.forename: Felix
authors.initials: F
authors.lastname: Nickel
authors.forename: Hannes G
authors.initials: HG
authors.lastname: Kenngott
authors.forename: Jochen
authors.initials: J
authors.lastname: Neuhaus
authors.forename: Christof M
authors.initials: CM
authors.lastname: Sommer
authors.forename: Tobias
authors.initials: T
authors.lastname: Gehrig
authors.forename: Armin
authors.initials: A
authors.lastname: Kolb
authors.forename: Matthias
authors.initials: M
authors.lastname: Gondan
authors.forename: Boris A
authors.initials: BA
authors.lastname: Radeleff
authors.forename: Anja
authors.initials: A
authors.lastname: Schaible
authors.forename: Hans-Peter
authors.initials: HP
authors.lastname: Meinzer
authors.forename: Carsten N
authors.initials: CN
authors.lastname: Gutt
authors.forename: Beat-Peter
authors.initials: BP
authors.lastname: Müller-Stich
mesh_terms: D000465:Algorithms; D000818:Animals; D002138:Calibration; D016629:Esophagectomy / Q000379:methods*; D004945:Esophagoscopy / Q000379:methods*; D004947:Esophagus / Q000033:anatomy & histology / Q000601:surgery; D057918:Fiducial Markers; D008198:Lymph Nodes / Q000033:anatomy & histology; D019047:Phantoms, Imaging; D015641:Radiography, Interventional / Q000295:instrumentation / Q000379:methods*; D012984:Software; D025321:Surgery, Computer-Assisted / Q000295:instrumentation / Q000379:methods*; D034421:Sus scrofa; D013552:Swine; D014057:Tomography, X-Ray Computed; D020535:Video-Assisted Surgery / Q000295:instrumentation / Q000379:methods*
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