DICOM Tag Morphing – Essential Ingredient in Enterprise PACS Archive

Herman Oosterwijk, principal of Otech Inc., reported his observations of the recent Society of Imaging Informatics in Medicine (SIIM, formerly SCAR) conference that was held in Providence, Rhode Island. In Herman’s article, he laments that it was hard to find anything “new”. I have heard much of the same, from several colleagues that were also in attendance.

I stopped attending the SCAR meetings several years ago, believing that many of the presentations either focused on updates of old subjects, or introduced concepts that were too impractical for commercial implementation. I decided to break my personal embargo in 2006 and attended the meeting in Austin, Texas. I came away with the same feelings that Herman expressed this year: “nothing new”. To me it seems as if there is a major disconnect between the subject matter of the papers in the meeting hall and the subject matter of the vendor booths in the exhibit hall. Perhaps I’m growing jaded, but if an idea is not compelling enough to quickly make its way into a commercial offering, is it worth looking at? At the 2006 meeting, one of the presenters suggested the time was right to replace the mouse with wireless video gamer gloves, sort of creating the diagnostic play station. Well the creators of the Nintendo Wii thought that was a good idea, but…

Actually I did mine some nuggets in Austin, but they were found on the other side of the street. I spent enough time in the Exhibitor’s Hall to discover several technologies that would prove to be the next new thing; “The PACS-neutral Enterprise Archive”.

In Herman’s June 15 story, he reported on an interesting paper presented by representatives from the Mayo Clinic. I’d love to give them credit here, but the SIIM papers are not yet available on-line.

Mayo has apparently constructed a massive central image archive that uses “16 servers for image archiving and provides access to more than 100 million images for tens of thousand of users”.

According to the paper, the Mayo Clinic uses “a commercial PACS only for short-term archiving (less than 3 months)”. Herman points out that this dual-tier storage strategy underscores “how much information goes back and forth between the image manager and long-term archive”. Actually it underscores how little data is going back and forth. Sizing the short-term cache on the PACS is all about matching the age of the priors. In this case, the heaviest recall is obviously within three months.

At any rate, the interesting point made in this article is;

“The presenters commented that the lack of standardization between the PACS image manager and the image archive could definitely be improved.”

Well, good luck. There are numerous reasons why even the current PACS do not “play well” with standalone DICOM archives, and I don’t believe for a minute that those reasons are technology challenges. I don’t see the PACS vendors giving up the Archive any time soon. Proprietary data objects or use of Private Tags simply locks the archive (and the data) to the PACS.

Therefore, the more practical strategy for anyone wishing to pair a PACS from one vendor with an Enterprise Archive from another is to expect that the PACS will continue to store some key meta data objects as proprietary objects, or store them as DICOM objects in Private Tags, or use proprietary Value Representations (the text that describes the encoding of the Tag).

The only way to defeat this particular marketing strategy is to deploy an Enterprise Archive that is capable of Tag Morphing. When confronted with a PACS that does not treat all key meta data objects as DICOM objects stored in Public Tags, the vendor can simply program the Archive to extract a copy of the meta data and convert it to a DICOM object and place it in a Public Tag, before committing it to the Archive’s long-term storage solution. The Image Header now contains the original PACS meta data and a copy placed by the Archive in a Public DICOM tag. When the originating PACS requests the data back, the original meta data objects (in their original format) are still where the originating PACS expects them to be.

If a different PACS were to request this data from the Enterprise Archive, there are two possibilities. If the second PACS is capable of reading Public DICOM Tags, the vendor of the second PACS can be given the Group and Element numbers of all the Public Tags where the meta data can be found in the Archived version of the image data file. If the second PACS cannot read the Public Tags, the Enterprise Archive can Morph the Image Header once again and transfer the copy of the meta data from its Public Tag to any Public or Private Tag that is utilized by the second PACS to store this meta data.

DICOM Tag Morphing is an intriguing example of “reverse engineering”, but it is not new or a stretch of the imagination.  It has been perfected over time by those individuals and companies that have been doing the dirty work of DICOM data migrations.   The library of their morphing experience is simply being put to use in the Archiving application.  Tag Morphing in the Enterprise Archive is the only practical solution today to deal with the inconsistencies in the way meta data is treated by many of the current PACS. You cannot hold your breath waiting for the PACS vendors to truly standardize.

I’ve found only three vendors that have deployed Enterprise Archives capable of Tag Morphing: Acuo Technologies, DeJarnette Research Systems, Emageon Inc. If there are others, they haven’t made this capability apparent.

I’ve written a few other pieces on this subject that can be found on this web site.

PACS-neutral Enterprise Archive – Who will build it?
Looking for a PACS-neutral DICOM Archive?
An Enhanced DICOM Archive would be the ticket!
PACS Vendors think PACS-neutral Archive is crazy idea
SCAR ’06 Update