Long-Term Image Archiving

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Images are getting larger in volume and quantity. As state and national laws mandate that healthcare organizations store these gigantic files for multiple years, storage system vendors are souping up their technologies that more efficiently manage dozens upon dozens of terabytes of data. And most hospitals today set up their PACS archive so that new studies are stored online for near-instant access and historical studies are moved to a reliable, cost efficient long-term data repository - keeping in mind in the long run that accessibility and retreivability are key.

Transitioning from a film room archive to an electronic storage system has its advantages, as well as challenges. The benefits include faster retrieval of historical studies, comparison of relevant priors, better management of images produced by new digital modalities, increased productivity and streamlined workflow.

On the other hand, storage technology is advancing quickly and prices continue to decline. What's "in" today may not necessarily be the technology choice of tomorrow. So how do you find a high-performing archive that is scalable, reliable and secure? And don't forget to factor in obsolescence protection and data migration, disaster recovery, business continuity and overall cost of ownership.

The good news is there are many options hospitals have when it comes to archiving medical images in a PACS environment. While a larger facility may opt for a system that stores new medical images on spinning disc technology and older studies in an onsite and offsite data repository, specialty hospitals and imaging centers may select to outsource their images to an offsite storage service provider (SSP).

To select the right storage system, decision-makers need to consider: "The size of each element of data that will be stored; the speed in which it needs to be retrieved; the cost per gigabyte for that storage; and its integration with different applications," says Tomas Hough, principal of True North & Consulting Associates. "Knowing these four points, you can then start to weigh out what is the best application for you given what your needs are."

One approach to storing medical images uses a hierarchical storage management (HSM) system where regularly accessed files are stored on high-speed hard drive arrays and then gradually migrated to some form of removable media for long-term storage. The declining cost of fiber-channel and ATA-based drive arrays, such as NAS (network attached storage) and SAN (storage area network) have started to change the paradigm.

Estimating that the diagnostic imaging department at the Medical College of Wisconsin would produce roughly 4 terabytes (TB) of data for every 100,000 studies, the facility installed a super advanced intelligent (AIT) tape library for their long-term archive. For online storage, the facility uses spinning disc on NAS. "We never ever pull from [the tape library]," says Paul Nagy, assistant professor of radiology and director of radiology informatics laboratory. "The only thing we use the tape for is a legal copy and or disaster recovery. We use an ATA drive on the NAS and we get away with that by saying that this is our convenient copy that is being used for interpretation and clinical use."

Long-term archives facilitate data migration, something Nagy insists all healthcare organizations must include in their storage plan. "Be aware of migration and exit strategies so that when you go with another vendor, you know how much is it going to cost to get the data back," instructs Nagy. "Don't expect that this is going to be your last vendor. Expect that this will be one vendor amongst many. It won't be your last archive either, so plan for the migration ahead of time because usually it's the most painful part."

HOW WILL MY ARCHIVE GROW?

When it comes to storage costs, there are three factors to consider, says Barbara Dumery, senior product manager of eMed Technologies: hardware for the server, software and the cost of storage. "The cost of storage depends on the type of storage it is and how much is needed," explains Dumery. Capacity is more often an approximation at the time of installation since image volume in most facilities is continuously increasing. As a result, the total cost of ownership for a hospital's long-term archive typically includes both initial and reoccurring costs.

"In the beginning, we did not anticipate annually that we would grow 25 percent," states Scott Dent, IT PACS Administrator