Which comes first the PACS or the VNA?


This is a question that several years ago was philosophical and interesting but not terribly relevant.  Today as the landscape is changing the answer for your organization is vital to your overall success.  Like all good questions the answer is….. It Depends!

First what do we mean by PACS  or VNA First?  It simply means in your environment after images are acquired, are they stored to a PACS, presumably for interpretation and then archived to the VNA for storage, or are they sent to the VNA first and then routed elsewhere.  As one might expect there are pros and cons to each strategy and the determination really relates to how each is used.  I hesitate to use the term workflow because it, like “train the trainer” is one of the overused terms in the industry.

A PACS first orientation is the more classical approach to a VNA.  The study is acquired by modalities, typically reviewed by a technologist at a PACS workstation in which demographics are verified.  There may be some study manipulation such as window leveling, deleting of images and general image QA.  Often times additional information is added in the form of scanned documents which can be anything from the insurance card, to technologist notes and worksheets.  Finally, the exam is marked as ready to be viewed by the physician or radiologist.  When the study is interpreted, and a report created the study is marked complete or reported.  At some point in this flow the study is put into the archive queue and it is sent on to the VNA.  In this flow the VNA is acting primarily as the archive, and in some cases is called the deep archive or cold archive.  If the study is ever needed again as a prior and it is not in local storage PACS will retrieve it as needed.

A VNA first orientation is a different flow.  After the images are acquired they are sent to a technologist imaging system.  At this step the image manipulation occurs, this can be done in a department-based system like a PACS, it could be on a dedicated QC workstation, web system or components in the VNA itself.  Then the study is sent to the VNA, which likely maintains a local cache, but could be a cloud-based system.  After the study is in the VNA it is ready to be read.  The study is then sent from the VNA to the reading station where the interpretation takes place.

One of the keys in the distinction between the two is how quickly the study is available in the VNA.  In a VNA first scenario the study is almost immediately available on the VNA.  This becomes important when there are multiple consumers of the image, such as an EMR integration that is serviced by the VNA not PACS.  A PACS first orientation the study is interpreted prior to archival which means the likelihood of the images changing is very low.  I would opine that the images should NOT change once they have been reported.  If they do, then an addendum is warranted.  This data flow also maintains a linear nature and is relatively simple.  There is value in simplicity and that should not be understated.   The downside of this is the time required for the image to get to the VNA and the relative inflexibility of the system.  If there is an issue with PACS or the study is “missed” it will not be available to downstream systems.

In the VNA first method there are multiple systems at play any of which could be down.  It is also a more complex workflow involving several steps.  The benefit however is near immediate access in downstream systems to the images as well as significant flexibility to integrate multiple data flows and systems.  A VNA first architecture allows for a reduced PACS footprint that can lower overall maintenance costs (often 15-20% annually of the PACS license cost).   It also supports the integration of multiple viewing systems for referring physicians, specialist viewers and outside contracted radiology groups.  I would also argue that it better supports the transition to PACS as a service or “deconstructed PACS” or PACS 3.0 whichever is your favorite term, as well as a multi facility multi PACS environment in which a single study needs to “live” in many places at once.

So back to the question, which is better?  It depends on what the current imaging needs are, in terms of access to images, how many systems are integrated and   what the future vision is for the system.  For simple systems stick with PACS first (your PACS vendor will love it!) if the intent is to implement more exotic workflows or there are multiple downstream systems it would be worth investigating a VNA first data flow.


Kyle Henson

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