IT spotlight: State-of-the-art VNA

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 - Boriz Zavalkovskiy
Boriz Zavalkovskiy

Medical image storage has become complex: People expect easy access to images, and with the proliferation of electronic health records (EHR), this includes physicians. Vendor-neutral archive (VNAs) technology provides a single consolidated enterprise image management system, eliminating silo storage of specialized images.

Since its inception, VNA technology has been promoted as the heir apparent to conventional PACS storage. If the proliferation of commercial VNAs exhibited at RSNA 2014 is an indicator, its time has come. 

Boriz Zavalkovskiy knows a lot about VNAs. He was part of a team at the Mayo Clinic that architected and developed the integration requirements for the very first VNA, a healthcare enterprise initiative undertaken in the early 2000s. Today, as the IT director of imaging systems and services at Stanford Health Care, Stanford, CA, he oversees the implementation and utilization of the enterprise’s Radinformatics talked with him about the current capabilities of VNAs, stumbling blocks that still need to be overcome and factors that will stimulate widespread adoption.

The main components of a VNA are an archive that has the ability to store and distribute the images it receives in a standard format and the software that makes this happen accurately, intelligently and expeditiously. The infrastructure of the software system incorporates components for data integrity, content management, image life cycle management, application workflows, image delivery and viewing and system self-monitoring.

Two kinds of VNAs

Zavalkovskiy identified two distinct types of VNA image archival systems: One is designed from inception to be a stand-alone neutral archive, a true VNA, and the other is built upon an existing PACS image storage platform. “They are differentiated by the fact that a true VNA does not have any workflows associated with clinical image management and workflow,” he explains “Rather it has a workflow for image archiving, retention, and distribution, in compliance with DICOM and the other standards of the images it contains.”

VNAs built upon an existing PACS platform have expanded their scope to include DICOM images of other medical specialties and to be able to store non-DICOM images that are, as Zavalkovskiy explains, “DICOM-ized”, essentially clothed in a DICOM wrapper. “If a VNA cannot be used independently of a PAC system, it has been designed as an extension of the existing PACS platform,” he specifies.

The VNA in use at Stanford accommodates any imaging standard format—such as JPG, TIFF, AVI files, and MPG files—that are commonly used in the worldwide web and a vendor-neutral DICOM archive. “If a VNA is DICOM-based, it doesn’t have standards for some types of images, and this will leave a large portion of an enterprise’s clinical practice unaddressed,” Zavalkovskiy says. “A VNA that creates a DICOM wrapper around the image—DICOM-izing the file—works from the perspective of storage and distribution, but it does not restore the image to its original format.”

The debate over DICOM versus true VNAs recalls the debates associated with reversible and irreversible image compression, he notes. There was a great deal of debate and concern regarding the stage at which a lossy compressed image would cease to be diagnostically useful versus lossless compressed images, which retained their original data integrity.

 Zavalkovskiy compares the DICOMized image to the lossy compressed images of the earliest PACS. It can be retrieved, but it cannot be restored to its original format, a deterrent to a clinician who needs to reference the original format. Accurate measurement isn’t possible, because the spatial resolution of a DICOMized image does not replicate the original.

He expects that this technical issue will be resolved at some time in the future, but for now, hospitals that use a DICOM-based VNA may have to to retain storage archives of non-DICOM images that could be needed in their original state.

The role of software

Although the truly enterprise VNA encompasses the ability to archive all medical images from all the systems that exist in the enterprise, it is not sufficient by itself. To be clinically useful, it has to integrate with the enterprise hospital information system and link to the episode of care, and that is accomplished via software.

The software needs to be able to accommodate storage, distribution, modality worklists and DICOM routing. Another factor to consider: retention of image policies