title: Computed radiography and direct radiography: influence of acquisition dose on the detection of simulated lung lesions.
abstract: OBJECTIVE
  We sought to evaluate the performance of dual-readout and single-readout computed radiography compared with direct radiography for detecting subtle lung abnormalities with a standard and a low-dose technique.
  
  
  METHODS
  Posteroanterior radiographs of an anthropomorphic chest phantom were obtained with a single-readout storage phosphor radiography system (CRS, pixel size 200 microm), a dual-readout storage phosphor radiography system (CRD, pixel size 100 microm), and a direct detector (DR, pixel size 143 microm) at dose levels of 400 and 800 speed. Ten templates were superimposed to project 4 types of lesions over low- and high-attenuation areas, simulating nodules, micronodules, lines, and patchy opacities. Six radiologists evaluated 60 hard-copy images for the presence or absence of lesions. Statistical significance of differences was evaluated using receiver operating characteristic analysis and analysis of variance.
  
  
  RESULTS
  For both low- and high-attenuation areas, CRD (Az = 0.85 and 0.66) was superior to CRS (Az = 0.75 and 0.58) for overall performance and all lesion subtypes (P < 0.05). DR (Az = 0.87 and 0.67) performed slightly better than CRD, being significant only for the detection of micronodules. Acquisition dose significantly affected only the detection of lines and micronodules, whereas the detection of nodules and patchy opacities was not significantly different with reduced exposure, regardless of the system used.
  
  
  CONCLUSIONS
  The dual-readout CR system significantly outperformed the single-readout CR and almost equaled the performance of DR. Dose reduction was more critical for small-sized lesions (micronodules, lines) than for nodular or patchy opacifications and affected mainly the lesions in high attenuation areas.
authors.affiliation: Department of Radiology, Medical University of Vienna, Vienna, Austria. martin.uffmann@univie.ac.at
authors.forename: Martin
authors.initials: M
authors.lastname: Uffmann
authors.forename: Mathias
authors.initials: M
authors.lastname: Prokop
authors.forename: Edith
authors.initials: E
authors.lastname: Eisenhuber
authors.forename: Michael
authors.initials: M
authors.lastname: Fuchsjäger
authors.forename: Michael
authors.initials: M
authors.lastname: Weber
authors.forename: Cornelia
authors.initials: C
authors.lastname: Schaefer-Prokop
mesh_terms: D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008171:Lung Diseases / Q000000981:diagnostic imaging*; D015588:Observer Variation; D019047:Phantoms, Imaging; D012372:ROC Curve; D011829:Radiation Dosage; D011856:Radiographic Image Enhancement / Q000295:instrumentation / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000295:instrumentation / Q000379:methods*; D014963:X-Ray Intensifying Screens