IMAGE QUALITY IN LOSSY COMPRESSED DIGITAL MAMMOGRAMS

The substitution of digital representations for analog images provides access to methods for digital storage and transmission and enables th e use of a variety of digital image processing techniques, including e nhancement and computer assisted screening and diagnosis. Lossy compre ssion can further improve the efficiency of transmission and storage a nd can facilitate subsequent image processing. Both digitization (or d igital acquisition) and lossy compression alter an image from its trad itional form, and hence it becomes important that any such alteration be shown to improve or at least not damage the utility of the image in a screening or diagnostic application. One approach to demonstrating in a quantifiable manner that a specific image mode is at least equal to another is by clinical experiment simulating ordinary practice and suitable statistical analysis. In this paper we describe a general pro tocol for performing such a verification and present preliminary resul ts of a specific experiment designed to show that 12 bpp digital mammo grams compressed in a lossy fashion to 0.015 bpp using an embedded wav elet coding scheme result in no significant differences from the analo g or digital originals. (C) 1997 Elsevier Science B.V.