Head orientation in CBCT-generated cephalograms

Abstract

Objective: To determine the reliability of obtaining two-dimensional cephalometric measurements using two virtual head orientations from cone-beam computed tomography (CBCT) models.Materials and Methods: CBCT scans of 12 patients (6 class II and 6 class III) were randomly selected from a pool of 159 patients. An orthodontist, a dental radiologist, and a third-year dental student independently oriented CBCT three-dimensional (3D) renderings in either visual natural head position (simulated NHP) or 3D intracranial reference planes (3D IRP). Each observer created and digitized four CBCT-generated lateral cephalograms per patient, two using simulated NHP and two using 3D IRP at intervals of at least 3 days. Mixed-effects analysis of variance was used to calculate intraclass correlation coefficients (ICCs) and to test the difference between the orientations for each measure. Results: ICC indicated good reliability both within each head orientation and between orientations.Of the 50 measurements, the reliability coefficients were >0.9 for 45 measurements obtained with3D IRP orientation and 36 measurements with simulated NHP. The difference in mean values of the two orientations exceeded 2 mm or 2° for 14 (28%) of the measurements. Conclusions: The reliability of both virtual head orientations was acceptable, although the percentage of measurements with ICC>0.9 was greater for 3D IRP. This may reflect the ease of using the guide planes to position the head in the 3D IRP during the simulation process. (Angle Orthod. 2009;79:971-977. © 2009 by The EH Angle Education and Research Foundation, Inc.