title: Detection of lung nodules on digital chest radiographs: potential usefulness of a new contralateral subtraction technique.
abstract: OBJECTIVE
  To evaluate the potential usefulness of a contralateral subtraction technique developed for radiologists' performance in the detection of subtle lung nodules on chest radiographs.
  
  
  METHODS
  Fifty chest radiographs (25 normal and 25 abnormal with a subtle lung nodule) that were digitized with a 0.175-mm pixel size and 4,096 gray levels were used. Twelve radiologists (10 attending and two residents) participated in observer tests and read both original and contralateral subtraction images with a sequential testing method. Radiologists' performance was evaluated by means of receiver operating characteristic analysis with use of a continuous rating scale. The beneficial and detrimental effects of the contralateral subtraction technique on the radiologists' performance were also evaluated.
  
  
  RESULTS
  The area under the receiver operating characteristic curve values obtained without and with contralateral subtraction images were 0.926 and 0.962, respectively. Results indicated that the contralateral subtraction images significantly (P <.05) improved diagnostic accuracy, particularly for radiologists with limited experience.
  
  
  CONCLUSIONS
  The contralateral subtraction technique can assist radiologists in the correct identification of subtle lung nodules on chest radiographs.
authors.affiliation: Department of Radiology, Saitama Medical School, Saitama, Japan.
authors.forename: Shunji
authors.initials: S
authors.lastname: Tsukuda
authors.forename: Atsuko
authors.initials: A
authors.lastname: Heshiki
authors.forename: Shigehiko
authors.initials: S
authors.lastname: Katsuragawa
authors.forename: Qiang
authors.initials: Q
authors.lastname: Li
authors.forename: Heber
authors.initials: H
authors.lastname: MacMahon
authors.forename: Kunio
authors.initials: K
authors.lastname: Doi
mesh_terms: D006801:Humans; D015588:Observer Variation; D011856:Radiographic Image Enhancement; D013902:Radiography, Thoracic / Q000379:methods / Q000706:statistics & numerical data; D003074:Solitary Pulmonary Nodule / Q000000981:diagnostic imaging* / Q000453:epidemiology; D013382:Subtraction Technique