A Vendor Neutral Archive (VNA) is a medical imaging technology in which images and documents (and potentially any file of clinical relevance) are stored (archived) in a standard format with a standard interface, such that they can be accessed in a vendor-neutral manner by other systems. This terminology is used as distinct from a traditional Picture Archiving and Communications Systems (PACS), although there is debate about where the boundary between a VNA and a PACS lies along the continuum of their common features.
Definition The simplest definition is "a medical device that stores medical images in a standard format with a standard interface, such that they can be accessed in a vendor-neutral manner by other systems". So-called "vendor neutrality" is implied by the standard format and interface, and the neutrality is with respect to vendor-specific devices that produce or consume those images (e.g., for display, distribution or analysis, with or without specific workflows, such as for radiology reporting, i.e., a PACS). The exact definition and feature set is contentious though, and evolves as different vendors of VNAs attempt to distinguish themselves from their competitors and avoid being excluded, and customers express desires ranging from pragmatic to fantastic. There is general agreement on the following key features:
Storage of DICOM images and related composite objects (presentation states, key objects, structured reports) DICOM network standard interface for storage, query and retrieval Administrative updates and corrections (patient ID changes and study merges) Scalability Each of the following features remain contentious, in the sense that some customers and vendors claim that some or all are fundamental to the concept, but others disagree:
Storage of objects not directly related to images (such as human-generated requests and reports) Storage of non-DICOM content (such as HL7 CDA documents) Non-DICOM access protocols (such as IHE Cross-Enterprise Document Sharing (XDS and XDS-I) Cross-domain identity and code resolution (patient ID, accession #, procedure codes) Dynamic DICOM tag morphing Information lifecycle management Exclusion of workflow management database content Independence from choice of database engine Audit trail of access
History
Evolution Traditionally, the need to store medical images has been most common in the radiology and nuclear medicine departments, and has been implemented in the form of sub-specialty and departmental (PACS), which have combined the functions of image management and image archiving into a single solution. Whilst such systems all have standard interfaces (DICOM and IHE) for ingestion and distribution of images over the network and on physical media (like CD), typically the workflow and optimal performance for display are achieved using proprietary software and protocols. Further, the persistent storage "inside" a proprietary PACS may not be in a standard form, the PACS may not update the stored files with the latest study and demographic updates and annotations stored in the database, and it may extend, abuse or depend on specific standard and non-standard (private) DICOM attributes in the stored files. Over time, in many implementations, the underlying storage infrastructure has been "factored" out of the traditional (PACS) at the hardware and file system (DAS, NAS, SAN) level, and are supplied instead by non-domain-specific computer data storage vendors. As more medical specialties incorporate images in their practice, the need to extend image storage and distribution capability to other departments, enterprise wide. Increasingly there is a desire to inter-operate at a higher application level, separating departmental-specific workflows, display and analysis solutions from image storage infrastructure, using standard protocols that are image and metadata aware, without sacrificing display performance. A complicating factor is that the (PACS) offerings are in a constant state of flux with respect to features and quality of service, and traditionally users will abandon one vendor and replace their product with another's every 3–5 years. This triggers the need to "migrate" the images and associated information to the new architecture without data loss, a non-trivial task despite the use of standard formats for image encoding. The concept of a VNA theoretically allows for greater stability (re-usability and less frequent migration) at the archive level, despite rapid evolution and change at the higher application-level (display and workflow). Of course, migrating from one vendor's VNA to another isn't trivial either, just hopefully less frequent. An alternative term for a VNA is a "PACS Neutral Archive", which perhaps better conveys the original intent, but this term is rarely used, and for better or for worse, VNA has become the buzzword of choice amongst customers and salesmen.
… excerpt ends here. Continue reading the full article.
