Cephalometric image analysis and measurement for orthognathic surgery |
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Authors: | Yang J Ling X Lu Y Wei M Ding G |
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Institution: | (1) Institute of Image Processing & Pattern Recognition, Shanghai Jiao-Tong University, Shanghai, China;(2) Department of Orthognathic Surgery, Shanghai Ganquan Hospital, Shanghai, China |
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Abstract: | Automatic identification of landmarks in cephalometry is very important and useful for orthognathic surgery. A computerised
automatic cephalometric analysis system (CACAS), based on image processing, is presented. For an original X-ray image, median
filtering and histogram equalisation are used to improve image quality. The edge of an X-ray image is detected by a wavelet
transform and Canny filter. Seventeen landmarks in cephalometry are successfully identified by knowledge-based edge tracing
and changeable templates. Seventy-three measurements based on distances, angles and ratios between landmarks are computed
automatically. The reliability of the landmarks and the validity of the measurements are compared for automatic and manual
operation. The values of measurements obtained by CACAS are more precise and reliable: the mean error for linear measurements
is less than 0.9 mm; the mean error for angular measurements is less than 1.2°. The rate of validity is over 80%, even if
the image quality is poor. For an image with a high signal-to-noise ratio, the rate of validity of landmarking and measurements
using the CACAS system is over 90%. |
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Keywords: | Orthognathic surgery Image processing Landmark identification Cephalometry |
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