Abstract
Cephalometry is a standard diagnostic tool in orthodontic and orthognathic surgery fields. However, built-in magnification from the cephalometric machine produces double images from left- and right-side craniofacial structures on the film, which poses difficulty for accurate cephalometric tracing and measurements. The cone-beam computed tomography (CBCT) images not only allow three-dimensional (3D) analysis, but also enable the extraction of two-dimensional (2D) images without magnification. To evaluate the most reliable cephalometric analysis method, we extracted 2D lateral cephalometric images with and without magnification from twenty full-cranium CBCT datasets; images were extracted with magnification to mimic traditional lateral cephalograms. Cephalometric tracings were performed on the two types of extracted 2D lateral cephalograms and on the reconstructed 3D full cranium images by two examiners. The intra- and inter-examiner intraclass correlation coefficients (ICC) were compared between linear and angular parameters, as well as between CBCT datasets of adults and children. Our results showed that overall, tracing on 2D cephalometric images without magnification increased intra- and inter-examiner reliability, while 3D tracing reduced inter-examiner reliability. Angular parameters and children’s images had the lowest inter- and intra-examiner ICCs compared with adult samples and linear parameters. In summary, using lateral cephalograms extracted from CBCT without magnification for tracing/analysis increased reliability. Special attention is needed when analyzing young patients’ images and measuring angular parameters.
Highlights
Dr Broadbent first established reproducible head positioning of the cephalostat in 1930 [1], which set a precedent for using lateral cephalometric radiographs in orthodontics
Even with proper exposure and head positioning, double images were present on the film, which made accurate cephalometric tracing difficult and led to tracing errors among orthodontic residents and clinicians [11]
We evaluated the inter-examiner reliability for each type of cephalometric analysis method (Figure 3B)
Summary
Dr Broadbent first established reproducible head positioning of the cephalostat in 1930 [1], which set a precedent for using lateral cephalometric radiographs in orthodontics. Slight underexposure or overexposure could yield an unacceptable image, which significantly increased tracing difficulty [6] Another drawback of conventional film was that errors during exposure could not be remedied. Even with proper exposure and head positioning, double images were present on the film, which made accurate cephalometric tracing difficult and led to tracing errors among orthodontic residents and clinicians [11]. With radiation exposure and cost significantly reduced since the initial introduction of CBCT, 3D imaging has become more widely used to replace several 2D X-rays images for diagnosis and progress evaluation [19]. Some clinicians and researchers suggest establishing new landmarks on CBCTs, and setting up a new 3D cephalometric tracing and analysis system [19]. The generated 2D lateral cephalometric X-Rays were traced in the “Digitize” function module in Dolphin Imaging (Figure 2G,H). For all data presented in this manuscript, p < 0.05 (*) was considered a suggestive difference, while p < 0.005 (**) was recognized as a statistically significant difference based on a recent recommendation [33]
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