title: Alveolar bone-loss area localization in periodontitis radiographs based on threshold segmentation with a hybrid feature fused of intensity and the H-value of fractional Brownian motion model.
abstract: OBJECTIVE
  Periodontitis involves progressive loss of alveolar bone around the teeth. Hence, automatic alveolar bone-loss (ABL) measurement in periapical radiographs can assist dentists in diagnosing such disease. In this paper, we propose an effective method for ABL area localization and denote it as ABLIfBm.
  
  
  METHODS
  ABLIfBm is a threshold segmentation method that uses a hybrid feature fused of both intensity and texture measured by the H-value of fractional Brownian motion (fBm) model, where the H-value is the Hurst coefficient in the expectation function of a fBm curve (intensity change) and is directly related to the value of fractal dimension. Adopting leave-one-out cross validation training and testing mechanism, ABLIfBm trains weights for both features using Bayesian classifier and transforms the radiograph image into a feature image obtained from a weighted average of both features. Finally, by Otsu's thresholding, it segments the feature image into normal and bone-loss regions.
  
  
  RESULTS
  Experimental results on 31 periodontitis radiograph images in terms of mean true positive fraction and false positive fraction are about 92.5% and 14.0%, respectively, where the ground truth is provided by a dentist. The results also demonstrate that ABLIfBm outperforms (a) the threshold segmentation method using either feature alone or a weighted average of the same two features but with weights trained differently; (b) a level set segmentation method presented earlier in literature; and (c) segmentation methods based on Bayesian, K-NN, or SVM classifier using the same two features.
  
  
  CONCLUSIONS
  Our results suggest that the proposed method can effectively localize alveolar bone-loss areas in periodontitis radiograph images and hence would be useful for dentists in evaluating degree of bone-loss for periodontitis patients.
authors.affiliation: Department of Computer Science and Information Engineering, Providence University, Shalu, Taichung 43301, Taiwan. Electronic address: lan@pu.edu.tw.
authors.forename: P L
authors.initials: PL
authors.lastname: Lin
authors.affiliation: Department of Computer Science and Engineering, National Chung Hsing University, Taichung 40227, Taiwan. Electronic address: powhei.huang@msa.hinet.net.
authors.forename: P W
authors.initials: PW
authors.lastname: Huang
authors.affiliation: Department of Computer Science and Engineering, National Chung Hsing University, Taichung 40227, Taiwan. Electronic address: phd9605@cs.nchu.edu.tw.
authors.forename: P Y
authors.initials: PY
authors.lastname: Huang
authors.affiliation: College of Oral Medicine, Chung Shan Medical University and Chung Shan Medical University Hospital, Taichung 40201, Taiwan. Electronic address: kunzelhsu@gmail.com.
authors.forename: H C
authors.initials: HC
authors.lastname: Hsu
mesh_terms: D000539:Alveolar Process / Q000000981:diagnostic imaging / Q000473:pathology*; D006801:Humans; D008953:Models, Anatomic; D010518:Periodontitis / Q000000981:diagnostic imaging / Q000473:pathology*; D011861:Radiography, Dental
keywords: Alveolar bone-loss; Hybrid feature; Leave-one-out cross validation; Periodontitis radiographs; fBm model