title: Multimodal registration of three-dimensional maxillodental cone beam CT and photogrammetry data over time.
abstract: OBJECTIVE
  In recent years, one of the foci of orthodontics has been on systems for the evaluation of treatment results and the tracking of tissue variations over time. This can be accomplished through analysing three-dimensional orthodontic images obtained before and after the treatments. Since complementary information is achieved by integrating multiple imaging modalities, cone beam CT (CBCT) and stereophotogrammetry technologies are used in this study to develop a method for tracking bone, teeth and facial soft-tissue variations over time.
  
  
  METHODS
  We propose a two-phase procedure of multimodal (Phase 1) and multitemporal (Phase 2) registration which aligns images taken from the same patient by different imaging modalities and at different times. Extrinsic (for Phase 1) and intrinsic (for Phase 2) landmark-based registration methods are employed as an initiation for a robust iterative closest points algorithm. Since the mandible moves independently of the upper skull, the registration procedure is applied separately on the mandible and the upper skull.
  
  
  RESULTS
  The results show that the signed error distributions of both mandible and skull registrations follow a mixture of two Gaussian distributions, corresponding to alignment errors (due to our method) and temporal change over time.
  
  
  CONCLUSIONS
  We suggest that the large values among the total registration errors correspond to the temporal change resulting from (1) the effect of treatment (i.e. the orthodontic changes of teeth positions); (2) the biological changes such as teeth growth over time, especially for teenagers; and (3) the segmentation procedure and CBCT precision change over time.
authors: Department of Computing Science, University of Alberta, Canada. E-mail: niousha@interchange.ubc.ca
authors: N
authors: N
authors: Bolandzadeh
authors: W
authors: W
authors: Bischof
authors: C
authors: C
authors: Flores-Mir
authors: P
authors: P
authors: Boulanger
mesh_terms: D000293:Adolescent; D000465:Algorithms; D059925:Anatomic Landmarks / Q000000981:diagnostic imaging; D002508:Cephalometry / Q000379:methods* / Q000706:statistics & numerical data; D002648:Child; D054893:Cone-Beam Computed Tomography / Q000379:methods* / Q000706:statistics & numerical data; D005147:Facial Bones / Q000254:growth & development; D005260:Female; D057918:Fiducial Markers; D005500:Follow-Up Studies; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods* / Q000706:statistics & numerical data; D021621:Imaging, Three-Dimensional / Q000379:methods* / Q000706:statistics & numerical data; D008297:Male; D008334:Mandible / Q000000981:diagnostic imaging / Q000254:growth & development; D008445:Maxillofacial Development / Q000502:physiology; D016011:Normal Distribution; D009805:Odontogenesis / Q000502:physiology; D009971:Orthodontics, Corrective; D010780:Photogrammetry / Q000379:methods* / Q000706:statistics & numerical data; D012886:Skull / Q000000981:diagnostic imaging / Q000254:growth & development