Purge your PACS: Deleting old images produces storage savings

2013 12 09 16 40 21 596 Binary 0s 1s 250 20131216213435

Looking for a simple way to extend the life of your PACS archive? Try deleting old images after their useful life is over, according to research presented at RSNA 2013. One institution found that using image life-cycle management with rules-based image deletion policies reduced growth in its PACS archive to nearly zero.

By adopting these deletion policies in its 13 image archives over the next year and a half, Ascension Health expects to save millions in storage media and future data migration costs, according to presenter Carol Joseph.

"We are in the process of purging our archives that are eligible, based on regulatory and local policy retention requirements, and putting daily deletion runs in place," she told AuntMinnie.com. "This process will help Ascension Health avoid significant storage media costs over the upcoming years."

Part of Ascension Health Alliance, Ascension Health is the largest Catholic health system, the largest private nonprofit health system, and the third largest health system based on revenues in the U.S., Joseph said. It operates in 23 states and the District of Columbia.

About three-quarters of Ascension Health's sites use a PACS from the same vendor, but they also have an archive at each health ministry. The remainder use PACS from different vendors. The health system has experienced dramatic annual growth in new imaging studies and today stores an average of 6.4 million new exams each year.

The average size of an imaging study has increased along with growing study volumes. In 2000, Ascension Health stored 252,000 studies at an average size of approximately 5 MB per study. By 2010, Ascension was storing 4.6 million studies at more than 20 MB per study, and by December 2012, average exam size had reached about 26 MB per study.

"Today we have well over 1 petabyte of data within our image archive for our primary images only," she said.

If Ascension continued on its prior path, the system was projected to be storing nearly 120 million new studies in its archive within 10 years, with the addition of 72 million new studies over that time period, Joseph said.

"When you multiply that by 25.6 MB per study ... in 2012 -- and we know that's growing -- that's going to be about 1,750 petabytes of new data, or 1.7 exabytes," she said. "So it's a huge and significant issue for us."

Taking action

After researching state and federal image retention requirements, the Ascension team was surprised to find that some states, such as Alabama, don't have any image retention requirements at all. Other states, such as Washington, require image retention for 10 years after final patient discharge.

"That information isn't necessarily kept in a PACS archive," Joseph said.

There are no federal requirements for image retention, but "Medicare does have the right to conduct audits to ensure you've provided the services you've billed for up to five years," she said.

As a result, Ascension decided to implement a default five-year image retention policy for those states without defined image retention requirements.

The group investigated image life-cycle management tools from vendors, some of which didn't have rules-based deletion capabilities. While the majority of Ascension's archives did have such tools, they weren't using them, Joseph said.

Ascension also looked at local retention policies at individual hospitals. Policies varied not only by hospital, but within different departments such as radiology, the cath lab, etc., in the same hospital.

"When you look across several hospitals in a health system, things got considerably worse," she said. "Getting folks to change policies can take a considerable amount of time, and that took quite a bit of work."

After testing and working with the vendor's software engineers to get the image life-cycle management tool to be 100% accurate and to be able to apply complex rule sets, they tested and validated that they could reuse the archive space gained by deleting old images, Joseph said.

"We have used the tool to delete seven years of old data from an archive and set up rules to run daily to delete images that have aged and now meet the deletion rule," she told AuntMinnie.com. "This has put the archive annual storage growth in a near-neutral pattern."

Implementing the new rules-based deletion program across Ascension Health should keep the health system at a cumulative storage volume of 40 million studies from 2013 to 2024, a little more than one-third of what the projected study volume would have been without adoption of these policies.

Cost avoidance

Joseph estimated that the initial archive cleanup of 166 terabytes (TB) based on the new policies will avoid costs of $296,000. Moving forward, annual cost avoidance is expected to reach $134,000 given the current annual storage rate of 75 TB. Over 10 years, the policies will save the health system $1.3 million -- and those numbers are conservative estimates, she noted.

"We know that these will be substantially higher because study size continues to grow," Joseph said.

Perhaps more importantly, the rules-based deletion polices will produce significant savings by avoiding future image migration costs. The initial 160 TB of archive cleanup will save $498,000 in future migration spending, followed by annual cost avoidance of $225,000. Total 10-year cost avoidance for future migration is projected to reach $2.25 million.

"This is on a small set of our archives, but it's going to be in the tens of millions of dollars in cost savings and cost avoidance over a period of time," she said.

Ascension expects to have 13 image archives cleaned up and in deletion mode within a year to 18 months, Joseph said.

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