By default, current versions (1.9.6 or later) of the Gateway software are configured to use lossy compression for locally storing studies, as well as transmitting studies to OnePacs, for all study types other than conventional radiography and mammography studies. (CR and MG studies use lossless compression, at a compression ratio of approximately 3:1). For lossy compression, the JPEG2000 algorithm with a compression ratio of 8:1 is used. The JPEG2000 algorithm was selected due to an established body of research demonstrating JPEG2000 to have optimal characteristics as a compression algorithm for medical imaging, including the ability to maintain excellent image quality even at high compression ratios (see “JPEG2000 Compression of Medical Imagery”, Proc. of SPIE Vol. 3980, Feb. 2000). The 8:1 ratio chosen for the default OnePacs installation is a conservative figure and for the large majority of uses, no perceptible change in image characteristics or quality will result from the compression.
Some users may wish to change the default compression settings, either to utilize lossless compression, or to increase or decrease the lossy compression ratio.
The compression used can be configured in the jmx-console, reached in a web browser at the following URL:
(On the gateway machine itself) http://localhost:8080/jmx-console
After login to the jmx console, select the “Service=StoreSCP” option. Scroll down the screen to find the “CompressionRules” item. Into the text box containing the compression rules, you may paste in one of the following options:
|JPLL||Compress all studies with JPEG lossless|
|J2KI||Compress all studies with JPEG2000 lossy|
You may also edit the “LossyCompressionQuality” item to change the compression ratio. The default value is 0.12, signifying an approximately 8 to 1 compression ratio (that is, the final image will be 0.12 times the size of the original image).
Implications of Compression for Archiving
Whatever compression method you choose at the Gateway will determine how studies are stored in the OnePacs system. If you are archiving studies with OnePacs, you may choose to either archive studies in a lossless format, or with lossy compression. Using lossy compression has the advantage of reducing file size, which reduces storage costs and transmission times. However, some facilities/groups may wish to archive studies only using lossless compression.
If you wish to have all studies for one or more facilities managed in the OnePacs system using only lossless compression, simply configure the Gateway(s) for such facility(ies) to utilize lossless compression. If studies are compressed using lossless compression at the Gateway, they will remain compressed with lossless compression for the remainder of their life cycle with OnePacs, including permanent archiving, if applicable.