title: Detection of artificial air space opacities with digital radiography: ex vivo study on enhanced latitude post-processing.
abstract: OBJECTIVE
  To evaluate in a.-p. digital chest radiograms of an ex vivo system if increased latitude and enhanced image detail contrast (EVP) improve the accuracy of detecting artificial air space opacities in parts of the lung that are superimposed by the diaphragm.
  
  
  METHODS
  19 porcine lungs were inflated inside a chest phantom, prepared with 20-50 ml gelatin-stabilized liquid to generate alveolar air space opacities, and examined with direct radiography (3.0 × 2.5 k detector/ 125 kVp/ 4 mAs). 276 a.-p. images with and without EVP of 1.0-3.0 were presented to 6 observers. 8 regions were read for opacities, the reference was defined by CT. Statistics included sensitivity/specificity, interobserver variability, and calculation of Az (area under ROC curve).
  
  
  RESULTS
  Behind the diaphragm (opacities in 32/92 regions), the median sensitivity increased from 0.35 without EVP to 0.53-0.56 at EVP 1.5-3.0 (significant in 5/6 observers). The specificity decreased from 0.96 to 0.90 (significant in 6/6), and the Az value and interobserver correlation increased from 0.66 to 0.74 and 0.39 to 0.48, respectively. Above the diaphragm, the median sensitivity for artificial opacities (136/276 regions) increased from 0.71 to 0.77-0.82 with EVP (significant in 4/6 observers). The specificity and Az value decreased from 0.76 to 0.62 and 0.74 to 0.70, respectively, (significant in 3/6).
  
  
  CONCLUSIONS
  In this ex vivo experiment, EVP improved the diagnostic accuracy for artificial air space opacities in the superimposed parts of the lung (area under the ROC curve). Above the diaphragm, the accuracy was not affected due to a tradeoff in sensitivity/specificity.
authors.affiliation: Klinik für Diagnostische Radiologie, Universitätsklinikum Schleswig-Holstein, Campus Kiel.
authors.forename: J
authors.initials: J
authors.lastname: Biederer
authors.forename: H
authors.initials: H
authors.lastname: Bolte
authors.forename: T
authors.initials: T
authors.lastname: Schmidt
authors.forename: N
authors.initials: N
authors.lastname: Charalambous
authors.forename: M
authors.initials: M
authors.lastname: Both
authors.forename: U
authors.initials: U
authors.lastname: Kopp
authors.forename: B
authors.initials: B
authors.lastname: Hoffmann
authors.forename: S
authors.initials: S
authors.lastname: Freitag-Wolf
authors.forename: R
authors.initials: R
authors.lastname: Van Metter
authors.forename: M
authors.initials: M
authors.lastname: Heller
mesh_terms: D000465:Algorithms; D000818:Animals; D001185:Artificial Intelligence; D003964:Diaphragm / Q000000981:diagnostic imaging*; D007089:Image Enhancement / Q000379:methods*; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D055613:Multiple Pulmonary Nodules / Q000000981:diagnostic imaging*; D015588:Observer Variation; D019047:Phantoms, Imaging; D011650:Pulmonary Alveoli / Q000000981:diagnostic imaging*; D011856:Radiographic Image Enhancement / Q000379:methods*; D013902:Radiography, Thoracic / Q000379:methods*; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*