Journal of Digital Imaging

, Volume 23, Issue 5, pp 517–518 | Cite as

Letter to the Editor Re: PanCanadian Evaluation of Irreversible Compression Ratios (“Lossy” Compression) for Development of National Guidelines

  • Geoff Norman
  • Peter Bak
  • Andre Matos
  • David A. KoffEmail author

Because of the important implications of the findings of the Pan-Canadian Evaluation of Irreversible Compression Ratios study,1 we have been approached to provide power estimates, or some other indication of the overall magnitude of the effect of compression on test characteristics. That is the intent of the present submission.

The concerns can be summarized into two broad categories: (1) is it possible that the few differences that were reported were simply statistical fluctuations, and can be safely discounted (a type I error)? And (2) is it possible that, at the level of individual comparisons, the sample size was so small that important differences were not detected (a type II error)? In this follow-up, we have decided to focus on indices of diagnostic performance (sensitivity, specificity, and accuracy) and not pursue measures of image quality, since performance is more central to an examination of the effect of compression.

With respect to the type I error concern, that is, the...


Image Quality Diagnostic Performance Compression Ratio Compression Algorithm Statistical Fluctuation 
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  1. 1.
    Koff D, Bak P, Brownrigg P, Hosseinzadeh D, Khademi A, Kiss A, Lepanto L, Michalak T, Shulman H, Volkening A: Pan-Canadian evaluation of irreversible compression ratios ("lossy"compression) for development of national guidelines. J Digit Imaging 22:569–78, 2009. Epub 2008 Oct 18CrossRefPubMedGoogle Scholar

Copyright information

© Society for Imaging Informatics in Medicine 2010

Authors and Affiliations

  • Geoff Norman
    • 1
  • Peter Bak
    • 2
  • Andre Matos
    • 2
  • David A. Koff
    • 2
    Email author
  1. 1.Department of Clinical Epidemiology and BiostatisticsMcMaster UniversityHamiltonCanada
  2. 2.Department of RadiologyMcMaster UniversityHamiltonCanada

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