The influence of lead thyroid collars on cephalometric landmark identification

ObjectiveTo investigate whether the application of thyroid collars (TCs) affects cephalometric landmark identification.Study designA 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.ResultsThe total mean error radius of the non-TC group (1.28 ± 1.47 mm) was smaller (P ≤ .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.ConclusionsPersonal 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.