title: Accuracy and reproducibility of automatic versus manual registration using a cone-beam CT image guidance system.
abstract: BACKGROUND
  Intraoperative imaging reveals morphologic changes and resolves anatomic uncertainties during surgery. The automatic registration (AR) approach provides registered intraoperative images for real-time tracking within seconds of acquisition.
  
  
  OBJECTIVE
  (1) To design an AR device for clinical use integrated with cone-beam computed tomography, (2) to compare the accuracy and reproducibility of manual and automatic registration, and (3) to evaluate the robustness of the AR system.
  
  
  METHODS
  An AR device consisting of an acrylic face shield with fiducials mounted on an adjustable arm was designed. Eight surface and five internal divot markers were placed with bony fixation to a cadaveric head. Internal markers were localized on the image representing the "true" location. This was compared to the positions localized using a navigational system when both manual registration and AR were applied. A series of surgical tasks and variation of the AR device height above the surgical field was performed, and target registration error (TRE) was measured.
  
  
  RESULTS
  The mean fiducial registration error (FRE) for manual and automatic registration was 0.72 mm ± 0.03 and 0.41 mm ± 0.01, respectively. The mean TRE for manual and automatic registration was 0.89 mm ± 0.26 and 0.91 mm ± 0.25, respectively.
  
  
  CONCLUSIONS
  AR offers a more accurate and reproducible FRE and a TRE equally comparable to that of manual registration. This system also demonstrates robustness with comparable accuracy and reproducibility throughout different surgical tasks and variation of AR device height up to 9 cm above the surgical field. This system is currently being translated into clinical trials.
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, University of Toronto, 2-344 Roselawn Avenue, Toronto, Ontario. dustin.dalgorf@utoronto.ca
authors.forename: Dustin
authors.initials: D
authors.lastname: Dalgorf
authors.forename: Michael
authors.initials: M
authors.lastname: Daly
authors.forename: Harley
authors.initials: H
authors.lastname: Chan
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Siewerdsen
authors.forename: Jonathan
authors.initials: J
authors.lastname: Irish
mesh_terms: D000465:Algorithms; D002102:Cadaver; D054893:Cone-Beam Computed Tomography / Q000295:instrumentation*; D006801:Humans; D007432:Intraoperative Period; D013517:Otorhinolaryngologic Surgical Procedures / Q000379:methods*; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D025321:Surgery, Computer-Assisted / Q000295:instrumentation*