Tuesday, December 1, 2009

Semi-neutral Archiving

"Vendor neutral archiving" is the current buzz-term from the 2009 RSNA meeting in Chicago. It is a requirement if an institution would like to have a single enterprise solution for all of its images. In most cases, additional sources of images after radiology are cardiology, surgery, endoscopy, as well as other specialties such as dentistry, and dermatology. Using an individual image archive for each department that generates medical images makes no sense. 

A single data repository for all medical images in an institution is driven, in part, by IT professionals who see this solution as achieving economies of scale for both physical infrastructure and administrative support. In addition, the increasing implementation of EMR technology literally demands a single source for image data. 

However, early experiences with trying to disconnect and isolate the archive component from the PACS have not always been easy or painless. Unfortunately, the IHE has not yet delivered a bulletproof profile, as the image manager and image archive do not yet have a standardized protocol and/or interface. Users have found that there is still proprietary information that is vendor specific in their archives. Also, archive performance has been reported also to be an issue. 

What should a system administrator do to prepare for transitioning their department to a shared, enterprise-wide archive? 

First, it is prudent to maintain the first archiving tier from the same PACS vendor. Images are still retrieved from this primary server, and retrievals for the first few days and/or weeks are served by this first tier archive. A copy can be sent to the vendor-neutral enterprise archive for distribution as part of the EMR. Image retrievals and/or pre-fetching of images after the roll-off date to the second archive (enterprise) tier (such as 1-3 months after implementation) will be from the enterprise archive. 

Second, a well defined interface specification, performance requirements and comprehensive acceptance testing should be part of the enterprise archive purchasing process. References from other sites who have implemented an enterprise archive using your flavor of PACS with that archive are important, too. 

One test I recommend conducting is to run a "compare" script. This will demonstrate that images are archived and retrieved in an identical fashion from both the PACS archive and the enterprise archive. Note that synchronization between tier 1 and tier 2 archives can be tricky, particularly when changes are made—such as modifying patient demographics—at one or the other archive level. Make sure that the DICOM standards that deal with Presentation States and Key Images are supported.