title: Validation of 3D-laser surface registration for image-guided cranio-maxillofacial surgery.
abstract: OBJECTIVE
  Image-data-based navigation plays an important role during surgical treatment in anatomically complex areas. Conventional patient-to-image registration techniques on the basis of skin and bone markers require expensive and time-consuming logistic support. A new markerless, high-resolution laser surface scan technique for patient registration has been tested in experimental and clinical settings.
  
  
  METHODS
  In a phantom study, a skull model was registered with laser scanning and marker-based algorithms. The registration procedure was repeated 25 times in each group. The values for the root mean-square error were calculated as a measure of the deviation of the forecast position from the actual position and the target difference. In a clinical setting, 21 consecutive patients who presented with cranio-maxillofacial disorders were scheduled for navigational surgery using laser surface scanning for patient-to-image registration. Here the accuracy was determined by anatomical landmark localization.
  
  
  RESULTS
  In the experimental study, a root mean-square error of 1.3+/-0.14 mm, and a mean target deviation of 2.08+/-0.49 mm were found for laser scanning. In contrast, a root mean-square error of 0.38+/-0.01 mm and a mean target deviation of 0.99+/-0.15 mm were found for marker registration. The differences were statistically significant (p<0.005). A strong correlation between the root mean-square error and the target deviation was found for laser (r=0.96) and marker registration (r=0.95). During the 21 clinical procedures, the overall accuracy of laser scan registration determined by the root mean-square error was 1.21+/-0.34 mm, and the mean clinical precision was 1.8+/-0.5 mm.
  
  
  CONCLUSIONS
  Three-dimensional laser surface registration offers an interesting approach for selected image-guided procedures in cranio-maxillofacial surgery.
authors.affiliation: Department of Oral and Maxillofacial Plastic Surgery, Tübingen University Hospital, Tübingen, Germany. juergen.hoffmann@uni-tuebingen.de
authors.forename: Jürgen
authors.initials: J
authors.lastname: Hoffmann
authors.forename: Carsten
authors.initials: C
authors.lastname: Westendorff
authors.forename: Christoph
authors.initials: C
authors.lastname: Leitner
authors.forename: Dirk
authors.initials: D
authors.lastname: Bartz
authors.forename: Siegmar
authors.initials: S
authors.lastname: Reinert
mesh_terms: D005145:Face / Q000000981:diagnostic imaging / Q000601:surgery*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D007834:Lasers; D008437:Maxilla / Q000000981:diagnostic imaging / Q000601:surgery*; D019047:Phantoms, Imaging; D025321:Surgery, Computer-Assisted / Q000295:instrumentation / Q000379:methods*; D014057:Tomography, X-Ray Computed