title: Reproducibility of three-dimensional cephalometric landmarks in cone-beam and low-dose computed tomography.
abstract: OBJECTIVE
  The purpose of this study is to compare the reproducibility of three-dimensional cephalometric landmarks on three-dimensional computed tomography (3D-CT) surface rendering using clinical protocols based on low-dose (35-mAs) spiral CT and cone-beam CT (I-CAT). The absorbed dose levels for radiosensitive organs in the maxillofacial region during exposure in both 3D-CT protocols were also assessed.
  
  
  METHODS
  The study population consisted of ten human dry skulls examined with low-dose CT and cone-beam CT. Two independent observers identified 24 cephalometric anatomic landmarks at 13 sites on the 3D-CT surface renderings using both protocols, with each observer repeating the identification 1 month later. A total of 1,920 imaging measurements were performed. Thermoluminescent dosimeters were placed at six sites around the thyroid gland, the submandibular glands, and the eyes in an Alderson phantom to measure the absorbed dose levels.
  
  
  RESULTS
  When comparing low-dose CT and cone-beam CT protocols, the cone-beam CT protocol proved to be significantly more reproducible for four of the 13 anatomical sites. There was no significant difference between the protocols for the other nine anatomical sites. Both low-dose and cone-beam CT protocols were equivalent in dose absorption to the eyes and submandibular glands. However, thyroid glands were more irradiated with low-dose CT.
  
  
  CONCLUSIONS
  Cone-beam CT was more reproducible and procured less irradiation to the thyroid gland than low-dose CT.
  
  
  CONCLUSIONS
  Cone-beam CT should be preferred over low-dose CT for developing three-dimensional bony cephalometric analyses.
authors.affiliation: Department of Oral and Maxillofacial Surgery, Cliniques Universitaires Saint Luc, Université Catholique de Louvain, Brussels, Belgium. raphael.olszewski@uclouvain.be
authors.forename: R
authors.initials: R
authors.lastname: Olszewski
authors.forename: L
authors.initials: L
authors.lastname: Frison
authors.forename: M
authors.initials: M
authors.lastname: Wisniewski
authors.forename: J M
authors.initials: JM
authors.lastname: Denis
authors.forename: S
authors.initials: S
authors.lastname: Vynckier
authors.forename: G
authors.initials: G
authors.lastname: Cosnard
authors.forename: F
authors.initials: F
authors.lastname: Zech
authors.forename: H
authors.initials: H
authors.lastname: Reychler
mesh_terms: D059925:Anatomic Landmarks / Q000000981:diagnostic imaging*; D002508:Cephalometry / Q000706:statistics & numerical data*; D054893:Cone-Beam Computed Tomography / Q000706:statistics & numerical data*; D005004:Ethmoid Bone / Q000000981:diagnostic imaging; D005123:Eye / Q000528:radiation effects; D005147:Facial Bones / Q000000981:diagnostic imaging*; D005624:Frontal Bone / Q000000981:diagnostic imaging; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000706:statistics & numerical data; D021621:Imaging, Three-Dimensional / Q000706:statistics & numerical data*; D008437:Maxilla / Q000000981:diagnostic imaging; D009295:Nasal Bone / Q000000981:diagnostic imaging; D009777:Occipital Bone / Q000000981:diagnostic imaging; D009915:Orbit / Q000000981:diagnostic imaging; D021362:Palate, Hard / Q000000981:diagnostic imaging; D010579:Petrous Bone / Q000000981:diagnostic imaging; D019047:Phantoms, Imaging; D056739:Pterygopalatine Fossa / Q000000981:diagnostic imaging; D011829:Radiation Dosage; D015203:Reproducibility of Results; D012886:Skull / Q000000981:diagnostic imaging*; D013100:Sphenoid Bone / Q000000981:diagnostic imaging; D013363:Submandibular Gland / Q000528:radiation effects; D013701:Temporal Bone / Q000000981:diagnostic imaging; D013819:Thermoluminescent Dosimetry / Q000295:instrumentation; D013961:Thyroid Gland / Q000528:radiation effects; D036542:Tomography, Spiral Computed / Q000706:statistics & numerical data*; D015050:Zygoma / Q000000981:diagnostic imaging