Sunday, September 11, 2011

PACS Migration Using A Standard-format Intermediate Offline Archive

Summary: Creation of an offline disposable archive of standard DICOM objects on an external transportable disk array is proposed as an approach to the PACS migration problem; an IHE profile has been proposed.

Long version:

This isn't actually going to be very long, since most of the content is elsewhere.

On the RCR Imaging Informatics Group there was a recent discussion of PACS migration that arose in the context of the existing contracts expiring some time soon (see "http://www.pacsgroup.org.uk/cgi-bin/forum/show.cgi?2/58490"). During the course of that there was discussion of DICOM "Part 10" format objects, that ultimately lead to a proposal for all PACS to be able to create a a new archive copy on an externally supplied filesystem (directly or network-attached) of standard DICOM files with a standard (lossless) compressed transfer syntax and all the "headers" up to date.

So, since it is that time of year once again, I put together an IHE brief proposal to define an Image Manager/Archive Content Migration Profile for this. Just swap "PACS" for "IM/IA" if you are not familiar with IHE-speak.

This is not a particularly new idea. I recall that many years ago Peter Kuzmak of the VA put forth some suggestions related to an interchangeable archive format for migration with some file system organization and naming as well as potential DICOMDIR-related changes in that context, but using DVD-R; I dug out his old presentation that was referenced from the minutes of the WG 5 meeting in Feb 2000.

Nowadays studies are so large and multitudinous that migrating them on thousands of CDs or DVDs would seem to be infeasible, but the low cost of consumer price-point hard drives and RAID boxes seem to suggest that making what is essentially a "throw away" copy of an entire PACS archive is nowadays realistic. It only needs to last long enough to be populated, reattached to the new PACS and its content imported. The DICOM standard already supports the notion of USB-attached media (physical media unspecified) to allow for flash drives and hard drives, although there may be details that need to be worked through for the sheer size of an entire PACS archive.

Anyway, it remains to be seen how the IHE Radiology Planning Committee receives this, and if they (well, we, since I am a member) don't reject it out of hand, and prioritizes it relative to other profile proposals (since the Technical Committee has limited bandwidth and each year only works on a small number of proposals).

So if any of you out there have any thoughts about whether this is a good idea or a terrible one, or suggestions for improvement of the proposal, please let me know.

1 comment:

Carlos Estevam said...

Hello, David!

That is something that should in a standard because it is not easy to create software to map database and filesystems for the process of backup. The PACS Dcm4chee, for example, stores data in a distinct format: if there is a need to move a big amount and maintain the compatibility for other PACs systems, it is almost impossible since there is no rules in DICOM related to retrieving those stored dicom files beyond the limitation of getting only each file and the need to read them all before knowing from which study/series/etc. each one belongs, or querying obsolete database information for objects that were linked with those informations only for immediate access, having no way to deal with offline storage media because those, as said, don't need to be stored by rules of DICOM standard.

Regards!