ABSTRACT
Landmarks, or certain characteristic reference points, on cephalograms are used as a diagnostic aid employed in treatment planning by orthodontists. This work presents an algorithm for recognizing some anatomical features and locating landmarks on lateral skull X rays (cephalograms) using digital image processing and feature recognition techniques. A cephalogram is digitized and stored in a computer memory. Prefiltering is applied to remove image noise. The bony and flesh profiles of jaw and front face are traced. Using these profiles the algorithm locates 17 points on the image, some on bony features and others on soft tissue. To locate these points, edge-enhancement, thresholding, and edge-detection techniques are applied. The algorithm can be run on an IBM compatible microcomputer.
Subject(s)
Cephalometry/methods , Image Processing, Computer-Assisted , Microcomputers , Orthodontics/methods , Algorithms , Image Enhancement/methods , Research DesignABSTRACT
This paper presents an algorithm for automatically locating certain characteristic anatomical points called landmarks on cephalograms (skull X-rays). These landmarks are used by orthodontists in diagnosis and treatment planning. The algorithm uses digital image processing and feature recognition techniques to locate the landmarks. A resolution pyramid of the digitized cephalogram is first created. The algorithm works on the smaller, lower resolution images to locate features of interest and moves to the bigger, higher resolution images if greater location accuracy is required. Prefiltering using the median filter, contrast enhancement using histogram equalization, and edge enhancement using different gradient operators are performed on the images. The algorithm uses anatomical knowledge of the human facial structure to search for features containing the landmarks. The accuracy of the algorithm in locating the landmarks is compared with values obtained from human experts. At present the algorithm attempts to locate 10 landmarks of 27 needed for a complete analysis. All 10 landmarks have been successfully located on five cephalograms of varying quality.