title: Markerless laser registration in image-guided oral and maxillofacial surgery.
abstract: OBJECTIVE
  The use of registration markers in computer-assisted surgery is combined with high logistic costs and efforts. Markerless patient registration using laser scan surface registration techniques is a new challenging method. The present study was performed to evaluate the clinical accuracy in finding defined target points within the surgical site after markerless patient registration in image-guided oral and maxillofacial surgery.
  
  
  METHODS
  Twenty consecutive patients with different cranial diseases were scheduled for computer-assisted surgery. Data set alignment between the surgical site and the computed tomography (CT) data set was performed by markerless laser scan surface registration of the patient's face. Intraoral rigidly attached registration markers were used as target points, which had to be detected by an infrared pointer. The Surgical Segment Navigator SSN++ has been used for all procedures. SSN++ is an investigative product based on the SSN system that had previously been developed by the presenting authors with the support of Carl Zeiss (Oberkochen, Germany). SSN++ is connected to a Polaris infrared camera (Northern Digital, Waterloo, Ontario, Canada) and to a Minolta VI 900 3D digitizer (Tokyo, Japan) for high-resolution laser scanning.
  
  
  RESULTS
  Minimal differences in shape between the laser scan surface and the surface generated from the CT data set could be detected. Nevertheless, high-resolution laser scan of the skin surface allows for a precise patient registration (mean deviation 1.1 mm, maximum deviation 1.8 mm).
  
  
  CONCLUSIONS
  Radiation load, logistic costs, and efforts arising from the planning of computer-assisted surgery of the head can be reduced because native (markerless) CT data sets can be used for laser scan-based surface registration.
authors.affiliation: Department of Cranio-Maxillofacial Surgery, University of Heidelberg, Heidelberg, Germany. Ruediger_Marmulla@med.uni-heidelberg.de
authors.forename: Rüdiger
authors.initials: R
authors.lastname: Marmulla
authors.forename: Tim
authors.initials: T
authors.lastname: Lüth
authors.forename: Joachim
authors.initials: J
authors.lastname: Mühling
authors.forename: Stefan
authors.initials: S
authors.lastname: Hassfeld
mesh_terms: D003626:Data Display; D005145:Face / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D007259:Infrared Rays; D007834:Lasers; D019647:Oral Surgical Procedures / Q000191:economics / Q000379:methods*; D010781:Photography / Q000295:instrumentation; D011446:Prospective Studies; D013238:Stereotaxic Techniques / Q000295:instrumentation; D025321:Surgery, Computer-Assisted / Q000191:economics / Q000379:methods*; D014057:Tomography, X-Ray Computed