title: Accurate frameless registration of MR and CT images of the head: applications in planning surgery and radiation therapy.
abstract: OBJECTIVE
  To evaluate the feasibility and efficacy of a three-dimensional image registration technique for planning skull base surgery, performing frameless image registration for stereotaxic neurosurgery, and staging nasopharyngeal carcinoma.
  
  
  METHODS
  Computed tomographic (CT) and magnetic resonance (MR) images from 35 patients were registered by identifying 12-16 homologous landmarks with each modality. Images were displayed as overlaid sections or rendered three-dimensional scenes. The clarity of the combined images from 15 patients undergoing skull base surgery was compared with that of the conventional displays.
  
  
  RESULTS
  Images were combined for three applications, with an accuracy of 1-2 mm. For the 15 patients undergoing skull base surgery, the combined images were significantly better at depicting the relationship between bone and lesion than conventional display (P < .01).
  
  
  CONCLUSIONS
  MR and CT images of the head can be accurately registered without using external markers or substantially altering image acquisition protocols. The resulting images can show the radiologic information more clearly than conventional viewing.
authors.affiliation: Division of Radiological Sciences, United Medical and Dental School, Guy's Hospital, London, England.
authors.forename: D L
authors.initials: DL
authors.lastname: Hill
authors.forename: D J
authors.initials: DJ
authors.lastname: Hawkes
authors.forename: M J
authors.initials: MJ
authors.lastname: Gleeson
authors.forename: T C
authors.initials: TC
authors.lastname: Cox
authors.forename: A J
authors.initials: AJ
authors.lastname: Strong
authors.forename: W L
authors.initials: WL
authors.lastname: Wong
authors.forename: C F
authors.initials: CF
authors.lastname: Ruff
authors.forename: N D
authors.initials: ND
authors.lastname: Kitchen
authors.forename: D G
authors.initials: DG
authors.lastname: Thomas
authors.forename: A
authors.initials: A
authors.lastname: Sofat
mesh_terms: D000328:Adult; D000368:Aged; D000465:Algorithms; D001932:Brain Neoplasms / Q000175:diagnosis / Q000601:surgery; D003198:Computer Simulation; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009303:Nasopharyngeal Neoplasms / Q000473:pathology / Q000532:radiotherapy / Q000601:surgery; D009367:Neoplasm Staging; D011880:Radiotherapy Planning, Computer-Assisted; D013238:Stereotaxic Techniques; D013813:Therapy, Computer-Assisted; D014057:Tomography, X-Ray Computed / Q000379:methods*