title: Accuracy of magnetic resonance imaging-cone beam computed tomography rigid registration of the head: an in-vitro study.
abstract: OBJECTIVE
  To evaluate the performance of cross-modality image registration procedure between magnetic resonance imaging (MRI) and cone beam computed tomography (CBCT).
  
  
  METHODS
  In vitro diagnostic MRI and CBCT images of 5 cadaver swine heads were obtained prospectively. Five radiopaque fiducial markers were attached to each cadaver skull by using resin screws. Automatic MRI-CBCT rigid registrations were performed. The specimens were then scanned using a 3-dimensional (3-D) laser scanner. The 3-D coordinate points for the centroid of the attached fiducial markers from laser scan were identified and considered ground truth. The distances between marker centroids were measured with MRI, CBCT, and MRI-CBCT. Accuracy was calculated by using repeated measures analysis of variance and mean difference values. The registration method was repeated 10 times for each specimen in MRI to measure the average error.
  
  
  RESULTS
  There was no significant difference (P > .05) in mean distances of the markers between all images and the ground truth. The distances' mean difference between MRI, CBCT, and MRI-CBCT and the ground truth were 0.2 ± 1.1 mm, 0.3 ± 1.0 mm, 0.2 ± 1.2 mm, respectively. The detected method error ranged between 0.06 mm and 0.1 mm.
  
  
  CONCLUSIONS
  The cross-modality image registration algorithm is accurate for head MRI-CBCT registration.
authors.affiliation: PhD Student, Orthodontic Graduate Program, School of Dentistry, University of Alberta, Edmonton, Alberta, Canada. Electronic address: m.alsaleh@ualberta.ca.
authors.forename: Mohammed A Q
authors.initials: MA
authors.lastname: Al-Saleh
authors.affiliation: Assistant Professor, Servier Virtual Cardiac Centre, Mazankowski Alberta Heart Institute and Department of Radiology and Diagnostic Imaging, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Kumaradevan
authors.initials: K
authors.lastname: Punithakumar
authors.affiliation: Assistant Professor, Department of Radiology and Diagnostic Imaging, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Jacob L
authors.initials: JL
authors.lastname: Jaremko
authors.affiliation: Assistant Professor, School of Dentistry, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Noura A
authors.initials: NA
authors.lastname: Alsufyani
authors.affiliation: Professor, Department of Computing Science, Faculty of Science, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Pierre
authors.initials: P
authors.lastname: Boulanger
authors.affiliation: Lead, School of Dentistry, Professor and Chair of the Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Paul W
authors.initials: PW
authors.lastname: Major
mesh_terms: D000465:Algorithms; D000818:Animals; D002102:Cadaver; D054893:Cone-Beam Computed Tomography / Q000379:methods*; D057918:Fiducial Markers; D006257:Head / Q000000981:diagnostic imaging*; D021621:Imaging, Three-Dimensional; D066298:In Vitro Techniques; D008279:Magnetic Resonance Imaging / Q000379:methods*; D013552:Swine