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A VNA and a Workstation Do Not Make a PACS!

February 27, 2012
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VNA's were not intended to replace departmental workflows.

Image previewIn a continuing series looking at the so-called Vendor Neutral Archive (VNA), this installment addresses the role a VNA can be expected to play in future PACS.  There are some who believe the VNA will become the core of all future PACS, replacing legacy PACS altogether.  I am not one of them!

The premise is that one can capitalize on the intelligence of a VNA to manage distribution of images to a diagnostic workstation, and thereby replace the PACS.  I would subscribe that such talk misses a key element of a PACS – Workflow, and that such functionality has never been a planned feature of a VNA. 

On the surface, the thought of being free to pick and choose PACS elements independently and to not be encumbered by a particular vendor is attractive.  On the other hand, PACS has been over twenty-five years in the making.  Over that time there has been a significant evolution in the capability of a PACS.  Perhaps the most significant thing has been the shift from a PACS-centric to a RIS-centric architecture in the case of radiology.  Modern-day RIS-centric PACS rely on the RIS to access the patient, and to launch the PACS for image display.  Reporting can be done via a speech recognition application, either stand alone or embedded within the RIS. 

Part of this workflow involves the interpretation of the study using the PACS.  A key aspect of a modern-day workflow is the ability to “lock out” other diagnosticians once dictation has been initiated.  This is part of the PACS workflow that spans the RIS, PACS, and speech recognition application.  Consequently, it is not just a workstation function.  Similarly, there may be changes to the image study during the interpretation.  The diagnostician may annotate some images, or save a specific presentation state.  The net result is a need to update the image storage with these changes.  Some PACS initially store the study in a short-term cache memory, and send the study to the long-term archive once it has been interpreted, to avoid multiple archive study changes. 

Another RIS-PACS workflow element is the interaction between image acquisition and interpretation.  How does a radiologist know when a study has been completed and is ready for interpretation?  Usually there are status messages that flow between the imaging device, RIS, and PACS that address the study status.  If a study is still being acquired, it might have a status of “in process,” whereas when the study has been completed within the RIS, the status changes to “ready for interpretation” and the study appears on the radiologist’s worklist.  When the radiologist opens the study and begins reporting, the status may change again to alert others that the study is being interpreted. 

It is functionality such as this that makes a workable departmental workflow.  If the expectation is that the legacy PACS can be eliminated by a combination of a VNA, RIS, and Workstations, where is this functionality to reside?  It is my opinion that one would simply be “reinventing the wheel” to move such functionality to where – the workstation?  The VNA? 

Vendors have spent years addressing the interoperability between systems to address these issues.  Granted, IHE (Integrating the Healthcare Enterprise) could be expanded to address all of the protocols within a PACS, but in reality this would simply be pushing the interoperability further down into the system, and to what end?  Just so one vendor’s workstation could plug and play with another vendor’s VNA, RIS or other system element? 

From my perspective, this is simply making a PACS (or more systems) out of a VNA.  I don’t dispute that there may be advantages to being able to easily adapt a third party’s advanced visualization application, but this is usually an additive capability to an existing PACS, not a PACS replacement.  Conversely, a full degree of VNA functionality has not resided within a PACS, so it is just as “additive” to add a VNA to a PACS. 

Last year I blogged on the “modularization” of PACS, but in the context of enabling the expansion of a legacy PACS not as a replacement.  I think this is still true and indicative of the additive nature of a VNA, not as a replacement of a PACS.  Another advantage of the VNA is the independent linkage to an Electronic Medical Record (EMR) that can enable a simple image viewer to access images without accessing the departmental PACS.  Again, I see this as an additive enterprise capability, not a PACS replacement.  The side benefit of the expansion of enterprise applications is that it allows departmental PACS to focus on what they do best – manage a particular “ologie’s” departmental workflow.

Feel free to comment.  I’d welcome the opinion of VNA vendors on whether they see their role as a PACS replacement!



Hi Joe, excellent post. Question - could the future of PACS be a 3-tiered system? VNA, Workstation and Workflow?

I ask this question because as you have probably noticed there are a number of vendors hitting the market that are touting workflow independent from the data source and display, driving integration and PACS workflow in the middle (dictation, worklist, locking, and modern web technologies for integration of external data sources).

By the way, I agree with you full in the context of this article but it begs the question, can workflow be added as an integrated component such that the "so called VNA" could still be the foundation for the next PACS, DICOM and non-DICOM content?

Acuo Technologies

I agree that there will likely be indepenent solutions such as workstations, but I don't know if anyone has extended the context to replace a PACS with a VNA. I don't know why there is the emphasis to "reinvent" the wheel by replacing the PACS. The primary reason for a VNA from my perspective is to integrate images across the enterprise -not replace departmental functionality! There is still a place for departmental solutions. I think it is better tfor the VNA to emphasize the benefits of enterprise image management and accessibility versus replacing departmental functions. This does not preclude specialized applications such as advanced visualization vendors improving on the workflow process in their own solution, and being able to pull images directly from a VNA. Therefore I think there is room for both solutions without having to turn the VNA into something it was not necessisarily designed for.