title: Effects of dual-energy subtraction chest radiography on detection of small pulmonary nodules with varying attenuation: receiver operating characteristic analysis using a phantom study.
abstract: OBJECTIVE
  The aim of this study was to investigate the detectability of simulated pulmonary nodules with different X-ray attenuation by flat-panel detector (FPD) chest radiography using a dual-exposure dual-energy subtraction (DES) technique.
  
  
  METHODS
  Using a FPD radiography system, we obtained 108 sets of chest radiographs of a chest phantom. They consisted of 54 sets each of chest radiographs with and without simulated nodules. Each data set contained a standard and a corresponding dual-energy subtracted chest radiograph (DES image). The diameters of the simulated nodules were 8, 10, and 12 mm, respectively; nodules of each size manifested attenuation of -450, -200, and 30 Hounsfield units (HU). We performed receiver operating characteristic (ROC) analysis to compare the observers' performance in detecting nodules.
  
  
  RESULTS
  For the -450 HU nodules the mean areas under the ROC curve (AUC) without and with DES images were 0.66 and 0.77, respectively; the difference was significant (paired t-test, P < 0.01). For nodules with -200 and 30 HU, there was no significant difference in the AUC value (0.79 vs. 0.77, P = 0.13; 0.92 vs. 0.94, P = 0.17, respectively).
  
  
  CONCLUSIONS
  The addition of DES images to standard chest radiographs improved the performance of radiologists charged with detecting simulated nodules with an attenuation of -450 HU.
authors.affiliation: Department of Diagnostic Radiology, Graduate School of Medical Sciences, Kumamoto University, Honjo, Kumamoto, Japan. seisei0430@nifty.com
authors.forename: Seitaro
authors.initials: S
authors.lastname: Oda
authors.forename: Kazuo
authors.initials: K
authors.lastname: Awai
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Funama
authors.forename: Daisuke
authors.initials: D
authors.lastname: Utsunomiya
authors.forename: Yumi
authors.initials: Y
authors.lastname: Yanaga
authors.forename: Koichi
authors.initials: K
authors.lastname: Kawanaka
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Yamashita
mesh_terms: D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging; D008175:Lung Neoplasms / Q000000981:diagnostic imaging; D019047:Phantoms, Imaging; D011237:Predictive Value of Tests; D012372:ROC Curve; D015900:Radiography, Dual-Energy Scanned Projection; D013902:Radiography, Thoracic; D012680:Sensitivity and Specificity; D003074:Solitary Pulmonary Nodule / Q000000981:diagnostic imaging*; D013382:Subtraction Technique