title: The influence of lead thyroid collars on cephalometric landmark identification.
abstract: OBJECTIVE
  To investigate whether the application of thyroid collars (TCs) affects cephalometric landmark identification.
  
  
  METHODS
  A randomized and observer-blinded diagnostic study with head films taken from 2 groups was undertaken, with 1 group wearing TCs during radiography (n = 100) and 1 group not wearing TCs (n = 100). The interobserver reproducibility of 15 landmarks was evaluated using 1-way analysis of variance and independent samples t test to compare the groups.
  
  
  RESULTS
  The total mean error radius of the non-TC group (1.28 +/- 1.47 mm) was smaller (P < or = .001) than that of the TC group (1.57 +/- 1.58 mm). Three landmarks located on the hyoid bone and on the second and third cervical vertebrae were identified as the main confounding factors.
  
  
  CONCLUSIONS
  Personal lead shielding of the thyroid gland affects landmark identification, but the overall clinical effect is negligible. Thyroid collars should be routinely applied during cephalometric radiography if cephalometric analyses are limited to structures above the second cervical vertebra.
authors.affiliation: Senior faculty member, Department of Orthodontics, Medizinische Hochschule Hannover, Hannover, Germany.
authors.forename: Dirk
authors.initials: D
authors.lastname: Wiechmann
authors.forename: Alain
authors.initials: A
authors.lastname: Decker
authors.forename: Ariane
authors.initials: A
authors.lastname: Hohoff
authors.forename: Johannes
authors.initials: J
authors.lastname: Kleinheinz
authors.forename: Thomas
authors.initials: T
authors.lastname: Stamm
mesh_terms: D000704:Analysis of Variance; D002508:Cephalometry / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D007854:Lead; D015588:Observer Variation; D019047:Phantoms, Imaging; D011835:Radiation Protection / Q000295:instrumentation*; D011859:Radiography; D015203:Reproducibility of Results; D016037:Single-Blind Method; D013961:Thyroid Gland / Q000000981:diagnostic imaging*
chemical_list: D007854:Lead