Comparison of landmark identification in traditional versus computer-aideddigital cephalometry

The aim of this study was to assess landmark identification on digital imag es in comparison with those obtained from original radiographs. Ten cephalo metric radiographs were selected randomly. Seven orthodontic residents iden tified 19 cephalometric landmarks on both the original radiographs and the digital images, To assess the concordance between landmarks identified on t he original radiographs and on their digital counterparts, the x, y coordin ates for each landmark in the 2 modalities were transformed with the identi cal references. The placement differences for 19 landmarks between 2 method s were calculated and their components in horizontal and vertical direction s were analyzed respectively. Multivariate analysis of variance showed that the "cephalometric radiograph" and "landmark" variation had greater influe nce than that from "method" (landmark identification on digital / original radiograph). It was also noted that the differences of landmark identificat ion between original radiographs and their digital counterparts were statis tically significant. The landmarks with significant differences of horizont al component on the x-axis were Me, Gn, ANS, PNS, LIA, The differences were generally under 1 mm with the exception of Or, Me, PNS, LIA. The landmarks with significant differences of vertical component on the y-axis were Po, Or, Gn. The inter-observer error for each landmark in digital images was ge nerally larger than that in the original radiographs. However, statisticall y significant differences of inter-observer errors between 2 modalities wer e only found for 4 of the 19 landmarks. These 4 landmarks, Po, Ar, ANS, and UM, should be scrutinized more carefully during potential applications of digital cephalometry.