title: Lung segmentation on standard and mobile chest radiographs using oriented Gaussian derivatives filter.
abstract: BACKGROUND
  Unsupervised lung segmentation method is one of the mandatory processes in order to develop a Content Based Medical Image Retrieval System (CBMIRS) of CXR. The purpose of the study is to present a robust solution for lung segmentation of standard and mobile chest radiographs using fully automated unsupervised method.
  
  
  METHODS
  The novel method is based on oriented Gaussian derivatives filter with seven orientations, combined with Fuzzy C-Means (FCM) clustering and thresholding to refine the lung region. In addition, a new algorithm to automatically generate a threshold value for each Gaussian response is also proposed. The algorithms are applied to both PA and AP chest radiographs from both public JSRT dataset and our private datasets from collaborative hospital. Two pre-processing blocks are introduced to standardize the images from different machines. Comparisons with the previous works found in the literature on JSRT dataset shows that our method gives a reasonably good result. We also compare our algorithm with other unsupervised methods to provide fairly comparative measures on the performances for all datasets.
  
  
  RESULTS
  Performance measures (accuracy, F-score, precision, sensitivity and specificity) for the segmentation of lung in public JSRT dataset are above 0.90 except for the overlap measure is 0.87. The standard deviations for all measures are very low, from 0.01 to 0.06. The overlap measure for the private image database is 0.81 (images from standard machine) and 0.69 (images from two mobile machines). The algorithm is fully automated and fast, with the average execution time of 12.5 s for 512 by 512 pixels resolution.
  
  
  CONCLUSIONS
  Our proposed method is fully automated, unsupervised, with no training or learning stage is necessary to segment the lungs taken using both a standard machine and two different mobile machines. The proposed pre-processing blocks are significantly useful to standardize the radiographs from mobile machines. The algorithm gives good performance measures, robust, and fast for the application of the CBMIRS.
authors.affiliation: Faculty of Engineering, Multimedia University, Persiaran Multimedia, Cyberjaya, Selangor, Malaysia. wshmunirah@gmail.com.
authors.forename: Wan Siti Halimatul Munirah
authors.initials: WS
authors.lastname: Wan Ahmad
authors.affiliation: Department of Electric, Electronic & Systems Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, Bangi, Selangor, Malaysia. wmdiyana@eng.ukm.my.
authors.forename: W Mimi Diyana W
authors.initials: WM
authors.lastname: Zaki
authors.affiliation: Faculty of Engineering, Multimedia University, Persiaran Multimedia, Cyberjaya, Selangor, Malaysia. faizal1@mmu.edu.my.
authors.forename: Mohammad Faizal
authors.initials: MF
authors.lastname: Ahmad Fauzi
mesh_terms: D000465:Algorithms; D016477:Artifacts; D016000:Cluster Analysis; D003287:Contrast Media; D066264:Datasets as Topic; D017143:Fuzzy Logic; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008168:Lung / Q000000981:diagnostic imaging*; D008952:Mobile Health Units; D008962:Models, Theoretical; D016011:Normal Distribution; D013902:Radiography, Thoracic / Q000295:instrumentation*; D012680:Sensitivity and Specificity
chemical_list: D003287:Contrast Media