| Summary: | 碩士 === 中臺科技大學 === 放射科學研究所 === 99 === Object: The aim of the study was to examine the intraobserver reliability of landmark identification in cone beam computed tomography (CBCT)-synthesized two-dimensional (2D) lateral cephalograms versus conventional digital cephalograms.
Materials and methods: Twenty CBCT scans and the corresponding conventional lateral cephalgrams were randomly selected. Two-dimensional lateral cephalograms were constructed from the three-dimensional (3D) CBCT scans by summing the voxels of the entire volume. All the images were imported into Winceph 8.0. Twenty landmarks in the CBCT-synthesized 2D cephalograms and conventional cephalograms were identified directly on the computer screen by an experienced orthodontist and the operation was repeated two weeks later. The x- and y-coordinates of each landmark were examined for intraobserver reliability. The differences in landmark reproducibility between the two modalities were analyzed with paired Student’s t-test.
Results: The horizontal and vertical errors of landmark identification by the two modalities of cephalometry ranged from 0.18 to 1.67 mm. Fewer landmarks in CBCT-synthesized cephalograms had intraobserver error greater than 1 mm. Significantly better reliability was observed in CBCT-synthesized cephalograms at Me, LIE and LIA in the horizontal dimension and at Pog, Gn, Me, UIA, LIA and LM in the vertical dimension. Scatter-plots revealed a characteristic pattern of error distribution for each landmark.
Conclusions: CBCT-synthesized lateral cephalograms is a promising method to replace conventional cephalograms for orthodontic diagnosis.
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