When PACS Pushes the Limit - Image Storage: The Basics

Twitter icon
Facebook icon
LinkedIn icon
e-mail icon
Google icon

 With image volumes surging every day, many healthcare facilities are re-evaluating their image storage strategies. And as more sites move toward filmless and paperless environments, the need for more storage space seems to be never-ending. Fortunately, as patient data, imaging studies and archived images increase, the cost of storage is coming down and choices in data storage are expanding.

Hospitals and imaging centers running out of disk space on their PACS are looking for ways to upgrade infrastructure to expand capacity. “We’re seeing growth all over, but specifically in cardiology and medical imaging, as we digitize more, the images are getting bigger and bigger, such as in digital mammography and 64-slice CT,” says Jonathan Goldberg, VP and CIO at St. Peter’s Healthcare Services in Albany, N.Y. “We’re seeing huge growth rates in terms of what the needs are.”

Facilities down the road and across the country are experiencing the same thing. Health Imaging & IT spoke with several that are revisiting their storage strategies. How to save short term? What to save long term? How can I guarantee immediate image access? They provide some answers on quenching the storage need.

Image storage overview

A PACS archive requires two levels of storage: short-term and long-term. The short-term or online storage is a temporary directory that receives files directly from the imaging modality, and typically stores images for 12 to 18 months on fast-access, spinning disk with a retrieval rate of two to five seconds per study on average. Long-term or near-line storage is the more permanent form of storage where images are housed for about two years.

PACS archives typically need networked storage, such as a storage attached network (SAN) — a network that connects storage devices to computers, or network attached storage (NAS) — a network that’s not attached to servers, allowing access to storage using network standard protocols. A SAN is about two and a half times more expensive than NAS because a SAN requires dedicated networks and costly gigabyte switches.

Forming a winning team

St. Peter’s Healthcare revamped its infrastructure in 2004 to manage the organization’s explosive data growth of about five to 10 terabytes per year. The healthcare network comprises 24 facilities, including a 450-bed hospital, specialty clinics, nursing homes and rehabilitation centers. “We were running out of space on our current storage,” Goldberg says, adding that when their Siemens Medical Solutions Sienet PACS was installed in 2004 it relied on an optical disk jukebox, and they were coming to the end of that capacity. “We knew at that growth rate, within four to six months, we’d be out of disk space.”

First, St. Peter’s looked into an expansion module they could simply plug into their current storage, but they soon realized that wasn’t practical in preparing for the future. They ultimately selected EMC Corporation to create a centralized, highly available storage infrastructure. Goldberg said they chose EMC because of the reputable relationship between Siemens and EMC, and the fact that Siemens PACS easily integrated with EMC CLARiiON NAS and EMC Centera content-addressed storage (CAS).

St. Peter’s merged radiology and cardiology PACS images, as well as other application storage onto both the CLARiiON and Centera to archive stores of data and to serve as their primary storage. The CLARiiON CX700 NAS system is designed for environments like St Peter’s that require high capacities (40 terabytes) and maximum application performance. It works best for heavy database applications, as it scales up to 76 TB with a modular pay-as-you-grow approach.

CLARiiON serves as St. Peter’s storage area network, storing all enterprise organizational data, including serving as the disk for their 100-plus virtual servers. Centera provides archive storage for medical images both in radiology and cardiology PACS.

St. Peter’s evolving storage infrastructure has cut data retrieval time for patient-critical from five minutes to only 30 seconds, Goldberg says. Physicians are extremely happy with it. “They like the response time, and they like the fact that they can go from study to study quicker. Now it’s an expectation that we’ve set,” he adds. “To them, it’s invisible. They have no idea it’s there. The only thing they know is that [images are available] a lot quicker.”

The new storage strategy has improved St. Peter’s customer satisfaction, made the infrastructure easier to