title: Impact of JPEG lossy image compression on quantitative digital subtraction radiography.
abstract: OBJECTIVE
  The aim of the study was to evaluate the impact of JPEG lossy image compression on the estimation of alveolar bone gain by quantitative digital subtraction radiography (DSR).
  
  
  METHODS
  Nine dry domestic pig mandible posterior segments were radiographed three times ('Baseline', 'No change', and 'Gain') with standardized projection geometry. Bone gain was simulated by adding artificial bone chips (1, 4, and 15 mg). Images were either compressed before or after registration. No change areas in compressed and subtracted 'No change-Baseline' images and bone gain volumes in compressed and subtracted 'Gain-Baseline' images were calculated and compared to the corresponding measurements performed on original subtracted images.
  
  
  RESULTS
  Measurements of no change areas ('No change-Baseline') were only slightly affected by compressions down to JPEG 50 (J50) applied either before or after registration. Simulated gain of alveolar bone ('Gain-Baseline') was underestimated when compression before registration was performed. The underestimation was bigger when small bone chips of 1 mg were measured and when higher compression rates were used. Bone chips of 4 and 15 mg were only slightly underestimated when using J90, J70, and J50 compressions before registration.
  
  
  CONCLUSIONS
  Lossy JPEG compression does not affect the measurements of no change areas by DSR. Images undergoing subtraction should be registered before compression and if so, J90 compression with a compression ratio of 1:7 can be used to detect and measure 4 mg and larger bone gain.
authors.affiliation: University of Ljubljana, Faculty of Medicine, Department of Stomatology, Slovenia.
authors.forename: A
authors.initials: A
authors.lastname: Fidler
authors.forename: B
authors.initials: B
authors.lastname: Likar
authors.forename: F
authors.initials: F
authors.lastname: Pernus
authors.forename: U
authors.initials: U
authors.lastname: Skaleric
mesh_terms: D000539:Alveolar Process / Q000000981:diagnostic imaging*; D000704:Analysis of Variance; D000818:Animals; D004195:Disease Models, Animal; D005096:Exostoses / Q000000981:diagnostic imaging; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008334:Mandible / Q000000981:diagnostic imaging; D008336:Mandibular Diseases / Q000000981:diagnostic imaging; D019252:Radiography, Dental, Digital / Q000379:methods*; D013223:Statistics as Topic; D018709:Statistics, Nonparametric; D013382:Subtraction Technique; D013552:Swine