Embedded wavelet region-based coding methods applied to digital mammography

In this paper, we investigate region-based embedded wavelet compression methods and introduce region-based extensions of the Set Partitioning In Hierarchical Trees (SPIHT) and the Set Partitioning Embedded bloCK (SPECK) coding algorithms applied to the breast region of digital mammograms. We have compared these region-based extensions, called OB-SPIHT and OB-SPECK, against the original SPIHT and the new standard JPEG 2000 on five digital mammograms compressed at rates ranging from 0.1 to 1.0 bits per pixel (bpp). Distortion was evaluated for all images and compression rates by the Peak Signal-to-Noise Ratio (PSNR). A comparison applying SPIHT and JPEG 2000 to the same set of images with the background pixels fixed to zero was also carried out. For digital mammography, region-based compression methods represent an improvement in compression efficiency from full-image methods, also providing the possibility of encoding multiple regions of interest.