title: Intraoperative computed tomography and automated registration for image-guided cranial surgery.
abstract: OBJECTIVE
  Two key problems for the use of navigation systems in image-guided surgery are accurate patient-to-image registration and the fact that with ongoing surgery the patient's anatomy is altered while the image data remains unchanged. A system for intraoperative CT imaging and fully automated registration of this image addresses both problems. It had been evaluated successfully in phantom studies. In this clinical study, we assessed the impact of the system on intraoperative workflow and registration accuracy in everyday patient care.
  
  
  METHODS
  In ten patients who underwent image-guided surgery, CT image data were acquired intraoperatively and were automatically registered in the navigation system. Registration accuracy and surgical outcome were assessed clinically. In six of these patients, a maxillary splint with markers had been inserted to cross-check registration accuracy. The target registration error of these markers was measured.
  
  
  RESULTS
  In all cases, registration accuracy was clinically sufficient and the surgical task could be performed successfully. In those cases where a maxillary template with target markers was attached for additional control of the registration accuracy, the target registration error was always better than 2 mm. Automated registration reduced the intraoperative registration time considerably and partially compensated for the time needed to perform the image data acquisition.
  
  
  CONCLUSIONS
  Intraoperative CT imaging and automated registration successfully address the two key problems of image-guided surgery. The method is robust and accurate and proved its usability in everyday patient care.
authors.affiliation: Department of Oral and Cranio-Maxillofacial Surgery, Heidelberg University Hospital, Im Neuenheimer Feld 400, 69120 Heidelberg, Germany. georg.eggers@med.uni-heidelberg.de
authors.forename: G
authors.initials: G
authors.lastname: Eggers
authors.forename: B
authors.initials: B
authors.lastname: Kress
authors.forename: S
authors.initials: S
authors.lastname: Rohde
authors.forename: J
authors.initials: J
authors.lastname: Mühling
mesh_terms: D000293:Adolescent; D000368:Aged; D000369:Aged, 80 and over; D003399:Craniotomy / Q000379:methods*; D005260:Female; D005547:Foreign Bodies / Q000000981:diagnostic imaging / Q000601:surgery*; D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging / Q000601:surgery*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D007430:Intraoperative Care; D008297:Male; D008875:Middle Aged; D008953:Models, Anatomic; D010363:Pattern Recognition, Automated; D011873:Radiology Information Systems; D025321:Surgery, Computer-Assisted; D014057:Tomography, X-Ray Computed; D014584:User-Computer Interface; D055815:Young Adult