title: Irreversible JPEG compression of digital chest radiographs for primary interpretation: assessment of visually lossless threshold.
abstract: OBJECTIVE
  To determine if digital chest images could be compressed in a primary interpretation context without perceived loss of fidelity (below the visually lossless threshold) at transilluminated film or cathode ray tube (CRT) display.
  
  
  METHODS
  One hundred forty-four posteroanterior radiographs were obtained with a digital chest radiography system. At both film and CRT display, an identified original image was presented side by side with a replicate, which was either an unaltered image or an image that had been Joint Photographic Experts Group (JPEG) compressed to 10:1, 20:1, or 50:1 and reconstructed. Each of the 10 readers indicated whether the replicate was "indistinguishable from the original" or "degraded" at clinical reading distance and at close inspection. The readers' ability to detect compressed images was examined for patterns; 95% CIs were used for statistical testing.
  
  
  RESULTS
  With transilluminated film at clinical reading distance, readers were as likely to rate originals (48 [20%] of 240 readings) as degraded as they were to rate 20:1 replicates (106 [22%] of 480 readings) as degraded, but they frequently identified 50:1 replicates (283 [59%] of 480 readings) as degraded. At close inspection, 20:1 replicates (163 [34%] of 480 readings) were often identified as degraded, but 10:1 replicates (19 [8%] of 240 readings) were not identified as degraded more often than originals (17 [7%] of 240 readings). With CRT display, the results were nearly identical.
  
  
  CONCLUSIONS
  At reading distance for primary interpretation, full-size digital chest radiographs that have been JPEG compressed to 10:1 or 20:1 and reconstructed are visually lossless at film or CRT display. Images compressed to 10:1 remain visually lossless at close inspection.
authors.affiliation: Electronic Radiology Laboratory, Mallinckrodt Institute of Radiology, Washington University School of Medicine, Box 8131, 510 S Kingshighway Blvd, St Louis, MO 63110, USA.
authors.forename: Richard M
authors.initials: RM
authors.lastname: Slone
authors.forename: Edward
authors.initials: E
authors.lastname: Muka
authors.forename: Thomas K
authors.initials: TK
authors.lastname: Pilgram
mesh_terms: D000465:Algorithms; D016477:Artifacts; D003626:Data Display; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008171:Lung Diseases / Q000000981:diagnostic imaging; D015588:Observer Variation; D011856:Radiographic Image Enhancement; D011858:Radiographic Magnification; D013902:Radiography, Thoracic; D012680:Sensitivity and Specificity; D012984:Software