title: Detection of subtle interstitial abnormalities of the lungs on digitized chest radiographs: acceptable data compression ratios.
abstract: OBJECTIVE
  To determine acceptable compression ratios for digital radiography, we evaluated the effect of data compression on the detection of subtle interstitial lung abnormalities using digitized chest radiographs.
  
  
  METHODS
  Screen-film chest radiographs of 38 patients with subtle interstitial lung abnormalities and 40 patients with normal lung parenchyma were digitized (spatial resolution, 0.175 mm; 2000 x 2000 pixels; 10 bits per pixel) and compressed with the discrete cosine transform method at ratios of 10:1, 20:1, and 30:1. Five chest radiologists and five radiology residents examined the uncompressed and compressed digital images and rates the presence of interstitial lung abnormalities with a five-level scale of confidence. Results were analyzed by receiver operating characteristic methods.
  
  
  RESULTS
  Overall, the interpretation of images with a compression ratio of 30:1 was significantly less accurate than that of uncompressed images (p < .05). For the five chest radiologists, interpretation of images with a compression ratio of 20:1 or 30:1 was significantly less accurate than that of uncompressed images (p < .05). However, for the five residents, no significant difference between interpretations of compressed and uncompressed images was noted (p > or = .05).
  
  
  CONCLUSIONS
  These results suggest that a 10:1 data compression ratio does not influence the detection of subtle interstitial lung abnormalities. However, information that is lost with a 20:1 data compression ratio might be essential for interpretation by experienced chest radiologists.
authors.affiliation: Department of Radiology, Osaka University Medical School, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Kido
authors.forename: J
authors.initials: J
authors.lastname: Ikezoe
authors.forename: H
authors.initials: H
authors.lastname: Kondoh
authors.forename: N
authors.initials: N
authors.lastname: Takeuchi
authors.forename: T
authors.initials: T
authors.lastname: Johkoh
authors.forename: N
authors.initials: N
authors.lastname: Kohno
authors.forename: N
authors.initials: N
authors.lastname: Tomiyama
authors.forename: H
authors.initials: H
authors.lastname: Naito
authors.forename: J
authors.initials: J
authors.lastname: Arisawa
authors.forename: H
authors.initials: H
authors.lastname: Nakamura
mesh_terms: D000328:Adult; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging*; D017563:Lung Diseases, Interstitial / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D012372:ROC Curve; D011856:Radiographic Image Enhancement