A comparison of wavelet and Joint Photographic Experts Group lossy compression methods applied to medical images

This presentation focuses on the quantitative comparison of three lossy com pression methods applied to a variety of 12-bit medical images. One Joint P hotographic Exports Group (JPEG) and two wavelet algorithms were used on a population of 60 images. The medical images were obtained in Digital Imagin g and Communications in Medicine (DICOM) file format and ranged in matrix s ize from 256 x 256 (magnetic resonance [MRI) to 2,560 x 2,048 (computed rad iography [CR], digital radiography [DR], etc). The algorithms were applied to each image at multiple levels of compression such that comparable compre ssed file sizes were obtained at each level. Each compressed image was then decompressed and quantitative analysis was performed to compare each compr essed-then-decompressed image with its corresponding original image. The st atistical measures computed were sum of absolute differences, sum of square d differences, and peak signal-to-noise ratio (PSNR). Our results verify ot her research studies which show that wavelet compression yields better comp ression quality at constant compressed file sizes compared with JPEG. The D ICOM standard does not yet include wavelet as a recognized lossy compressio n standard. For implementers and users to adopt wavelet technology as part of their image management and communication installations, there has to be significant differences in quality and compressibility compared with JPEG t o justify expensive software licenses and the introduction of proprietary e lements in the standard, Our study shows that different wavelet implementat ions vary in their capacity to differentiate themselves from the old, estab lished lossy JPEG, Copyright (C) 1999 by W.B. Saunders Company.