As the volume and variety of medical images increases, providers are looking for better ways to store and access them. Vendor neutral archives are fast finding favor – but in many respects the jury is still out on just what a VNA is, and what it should offer.

According to Frost and Sullivan, the market for VNA will hit $210 million by 2018. Driving this growth is the increasing need to more easily share imaging information between healthcare providers.

This market is still considerably smaller than the one for traditional picture archiving and communications systems, which are vendor-specific, but while the PACS market is showing slow growth, the market for VNAs is growing much more rapidly – about 15 percent CAGR.

According to a 2012 study by BridgeHead Software, about one-third of American hospitals had adopted a VNA, and another 19 percent were planning on adopting one in the next two years.

The distinguishing characteristic of a VNA is that it can handle many different types of images and associated data without being locked into the products of a single vendor. As medical imaging archives expand to include many different types of data – as well as image files from multiple departments and organizations – this is becoming increasingly important.

"A VNA separates out the archival functionality from the PACS," says Mike Leonard, director of product management for healthcare IT services at Iron Mountain, a Boston-based archiving company. "With a VNA you minimize the need for future migration because organizations switch PACS over time."

VNA separates the imaging layer from the archiving layer and makes it easier to share images across users. This vendor neutrality eliminates many of the headaches associated with data migration or using images from different sources.

Usually, importing an object from a PACS means involving the PACS vendor to handle the translation. "PACS has account control over PACS customers," Leonard points out.

This is time consuming and expensive. That might have been tolerable when imaging was confined to one department, but as imaging archives have grown to encompass multiple departments, or even multiple healthcare facilities, it's rapidly becoming insupportable.

Another contributing factor to the growth of VNAs is the Stage 2 meaningful use requirement for increased electronic sharing of medical records, including images.

Stage 2 doesn't require a VNA, but it does encourage sharing images and associated data among departments and organizations. According to one of the menu options, providers must receive 10 percent of their imaging via electronic health records.

Currently, the "standard" for medical imaging is DICOM, which stands for Digital Imaging and Communications in Medicine. Unfortunately, however, DICOM doesn't fully specify the contents of the metadata fields used to identify and annotate objects, and vendors have interpreted metadata differently – creating a plethora of incompatible formats within DICOM.

To further confuse matters, "VNA" has become a buzzword in the medical imaging marketplace and many products are being touted as VNAs that don't actually meet the criteria for vendor neutrality.

"The definition of VNA is definitely evolving," says Leonard. "We have different organizations using different definitions to suit their own needs, but the main features and functions are starting to solidify. It will take another couple of years for everyone to agree on what a VNA is."

So, what the heck is a VNA?

There is no standard definition of a VNA, so various vendors have published their own. For example, according to Iron Mountain, a VNA:

• Must interface with other clinical systems and disparate PACS for the purpose of communicating imaging data, by means of DICOM
• Must interface with other clinical information systems for communication of reports, results, workflow, etc. by means of HL7
• Must have the ability to store the complete suit of DICOM SOP classes including presentation states and key image notes
• Must store all objects in a non-proprietary format such as DICOM part 102
• Must support the most inclusive DICOM query/ retrieve specification as a service provider for information stored in the archive at all information levels
• Must provide context management, i.e., the ability to manipulate DICOM tags so as to convert the DICOM implementation and demographic needs of one PACS vendor (or imaging application) to the DICOM expectations of another PACS vendor (or imaging application) with no significant impact on the customer's daily operation. Context management includes the ability to prepare a PACS  through HL7 for ingestion of images from another, disparate PACS
• Must handle ADT updates to image files stored in the archive
• Must support a wide variety of store infrastructure solutions so as to facilitate storage hardware upgrades and replacement with little impact on the clinical enterprise
• Must include a separate, independent, commercially available database product which supports SQL, as as to allow for easy integration with an IT department's everyday management operations
• Must ingest any type of electronic document through the use of an API and characterize that information with the lowest level association that can be made within the archive.

This lack of standardization means prospective purchasers must look closely at the specification of vendors' products to see which will meet their needs for vendor neutrality, interoperability and conformance to open standards.

According to Leonard, there are several reasons why VNA isn't being even more widely adopted.

"Overall, there's still a lack of understanding of what a VNA is," he says. "There's also trepidation at switching your archiving strategy. That can be a pretty big change."

Also, "Cost is often seen as a barrier – as if a VNA is an all or nothing proposition," says Leonard. "In reality VNA can be staged over time. It doesn't have to be a forklift shift. That's becoming a common way to apply VNA."