title: The effect of JPEG2000 compression on detection of skull fractures.
abstract: OBJECTIVE
  To investigate the effect of the Joint Photographic Experts Group (JPEG2000) 30:1 and 60:1 lossy compression on the detection of cranial vault fractures when compared to JPEG2000 lossless compression.
  
  
  METHODS
  Fifty cranial computed tomography (CT) images were processed with three different level of JPEG2000 compression (lossless, 30:1 lossy, and 60:1 lossy) creating three sets of images. These were presented to five musculoskeletal specialists and five neuroradiologists. Each reader read at two of the three compression levels. Twenty-two cases contained a single fracture; the remaining 28 cases contained no fractures. Observers were asked to identify the presence or absence of a fracture, to locate its site, and rate their degree of confidence. Receiver operating characteristic (ROC), jackknife free-response receiver operating characteristic (JAFROC) and the Dorfman-Berbaum-Metz multiple reader multiple case (DBM-MRMC) analyses were used to explore differences between the lossless and lossy compressed images.
  
  
  RESULTS
  JPEG2000 lossless and 30:1 lossy compression demonstrated no significant difference in their performance with JAFROC and DBM-MRMC analysis (P < .416); however, JPEG2000 30:1 lossy compression demonstrated significantly better performance than 60:1 lossy compression (P < .016). A significant increase in misplaced confidence ratings was also seen with 60:1 (P < .037) over 30:1 lossy and lossless compression.
  
  
  CONCLUSIONS
  JPEG2000 60:1 compression degrades the detection of skull fractures significantly while increasing the confidence with which readers rate fractures compared with 30:1 lossy and lossless compression. JPEG2000 30:1 lossy compression does not significantly change performance when compared to JPEG2000 lossless for the detection of skull fractures on CT.
authors.affiliation: Discipline of Medical Radiation Sciences, Faculty of Health Science, University of Sydney, 75 East Street, Lidcombe, East Street, Sydney, 2141, Australia. mark.mcentee@sydney.edu.au
authors.forename: Mark F
authors.initials: MF
authors.lastname: McEntee
authors.forename: Ines
authors.initials: I
authors.lastname: Nikolovski
authors.forename: Roger
authors.initials: R
authors.lastname: Bourne
authors.forename: Mariusz W
authors.initials: MW
authors.lastname: Pietrzyk
authors.forename: Michael G
authors.initials: MG
authors.lastname: Evanoff
authors.forename: Patrick C
authors.initials: PC
authors.lastname: Brennan
authors.forename: Kevin L
authors.initials: KL
authors.lastname: Tay
mesh_terms: D000465:Algorithms; D044962:Data Compression / Q000379:methods*; D006801:Humans; D015588:Observer Variation; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012887:Skull Fractures / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed / Q000379:methods*