What ever happened to “deconstructed PACS”? More to the point, what would it take to achieve?

Several years ago, “deconstructed PACS” was the hot topic, also called PACS as a service, PACS 2.0, PACS 3.0, de-coupled PACS etc.  During that time many organizations made purchases based on the idea.  These were often a Vendor Neutral Archive (VNA) and a Zero Footprint Viewer (ZFV) for web and EMR viewing of radiology images.  Dictation systems have remained constant and have for the most part always been separate from the PACS.  There are several global worklist companies out in the market that have been around for a long time.   For the most part these worklist systems have been focused on the needs and requirements of teleradiology and large radiology groups.  That said they do a very good job of consolidating multiple sources of data, usually many hospitals and EMRs into a single worklist and assignment engine to get the right radiologist to read the study at the right time.  With all of this technology, why have we not seen the panacea of a deconstructed PACS come to fruition?

The answer surprisingly is that as an industry we have focused on many of the hard problems and forgotten that we still need a system to do what the PACS of yore did, and that is a departmental workflow system for the technologists.  There are several functions that need to occur before image data can be submitted into the machinery of the Enterprise Imaging Systems.  These are, while seemingly mundane extremely important:  DICOM Modality Worklist, Document Scanning, Quality Control (QC) and image management, and order validation, all tasks that are completed by the traditional PACS.  We will explore each of these in turn.

DICOM Modality Worklist (DMWL) is essential, as it ensures that images match an order, and all demographics are correct.  In my belief, a manual process is a broken process and typing in a 16 character accession number correctly is a recipe for disaster. In short something must provide DMWL and it should be used in all cases.

Document Scanning is an area I struggle with as in this day and age we should be able to remove all paper from the process.  I firmly believe that the only documents to be scanned, or electronically completed are documents that are required to be viewed by the radiologist and will alter the diagnosis.  This MUST be stored as a series with the images.  I submit that there is probably a better place for the data (the EMR) but that is another topic.

QC and image manipulation is simply verifying that the images are good and possibly adjusting the window/level.  There is sometimes a need for splitting, merging, deleting and moving images but this has gone down over the years and most of this is done at the modality.  The main point of this step is that this is the last opportunity for a technologist to review the study.  As soon as the image is released it becomes “ready to read” and will be picked up by a radiologist somewhere in the ether.  Given that in the new model it is unlikely that the tech can walk down the hallway and speak to the radiologist this step gains significance.  Like a bad picture on the internet, once it is out, it can’t be taken back.

The final task is order validation, with consistent use of DMWL this step should be not necessary, but in the real-world things happen.  In a distributed system where the worklist is driving reads from HL7, any study that does not match an order will not be read.  It can’t, as the dictation system needs to respond to an order with the report.  The viewer can’t launch it because the accession number does not match an order.  This last verification step is a gatekeeper step to ensure that every study has an order, as my old coach said, “no pass, no play”.

Again, PACS does all of these tasks, so what happens in a deconstructed model?  These tasks could be performed by the incumbent PACS, however most of the old guard has an inflated pricing structure and huge service maintenance contracts.  They tend to be not interested in this market, (or even the imaging center market).  Most of the smaller PACS companies are fixated on the diagnostic reading license and will not un-bundle the software at a relative price point to service this need.  We need a vendor or vendors to supply a light weight low cost departmental workflow system to feed into the enterprise imaging stack.  The only thing holding us back from deconstructing PACS is performing the simplest tasks that PACS does at the right price.  My challenge to the vendors out there is, who wants to fill this need and gain a footprint in almost every large organization?  Bear in mind that as a component of enterprise imaging this could be a foot in the door to then service one of the other components…. I would think that would be an attractive proposition, but the market has not responded thusly.

Is a Zero Footprint Viewer for a Radiologist’s Read the Right Tool for the Job?

 A zero-footprint viewer is an image viewer that runs completely in a web browser and does not require anything to be installed on the computer running it.  This is in direct contrast to the “thick” or “thin” client web viewers, or dedicated viewing workstations.  There are, of course, benefits to a zero-footprint viewer.  Firstly, as there is nothing to install, it does not require the user to have admin-level privileges.  Also, these viewers are presumed to be browser and OS agnostic.  Meaning, it should run on PC or MAC; Chrome, IE, Safari, and the like.  Zero-footprint viewers are now capable of displaying full DICOM image sets, as well as various levels of compression from lossless to lossy. As vendors continue to add more and more tools to these viewers, they can satisfy the needs of a much larger group of physicians.  Encompassing a variety of specialties and image sets, including cardiology and visible light. The ability for physicians to view images anywhere, including on a mobile device, is huge step forward for the industry and can potentially provide dramatic improvement in patient care, as images are no longer “locked” at a specific location.

Where I diverge from trending industry-think is in the idea that every radiologist viewer should be zero-footprint.  Radiology standards, when viewing and interpreting images, are necessarily high.  First and foremost, when following industry standards, a radiologist requires the use of DICOM calibrated monitors. For “diagnostic” monitors there should be a QA program in place to validate the calibration of the monitor and its ability to display the full depth of data in the radiology image.  In addition to the need for diagnostic quality monitors, a radiologist typically dictates into a voice recognition system to generate a report.  There are indeed cloud-based dictation solutions and, while it is possible for a radiologist to type a report directly into the EMR, these are not the norm for primary interpretation.  The industry dominant voice recognition system, used by the majority of radiologists, requires its application to be installed on a workstation, running windows OS.  It is very difficult to have this software running on one PC but pointing to two different versions or implementations.  It is in effect one dictation client per PC.  Combined, these two factors generally limit radiologists, in my experience, to an average of 2-3 physical locations in which they dictate.  This is important, as here is where we begin to see the technology trade-offs of having a zero-footprint viewer.  First in that a web browser, such as IE or Safari, does not have a reliable way of determining how many monitors are being used on the workstation (a typical read configuration has 3 monitors) nor how to best utilize that real estate. And, second is that speed is paramount.  When comparing viewers if there is a compromise between features and responsiveness to be made, most radiologists that I’ve worked with will, within reason, choose speed.  The zero-footprint viewers tend to do well on a good network, but over a high latency low bandwidth network it is very difficult to provide lightning fast response times.  In this type of instance, a client-based viewer can download full data sets in the background and pre-cache data for viewing, i.e. it is loading the next case.  Additionally, while the zero-footprint will probably beat the client in time-to-first-image, often the client-based viewer will win during significant image manipulation.  Overall, the client is more resilient to the inherent variability of a network connection.  So, given that a radiologist is, more often than not, reading from a pre-defined set of locations, which require specific physical hardware in terms of monitors and a dedicated dictation application, is there a superior advantage to the radiologist in having a zero-footprint viewer?  I submit that, currently, there is not one.

I believe that, as an industry, we need BOTH zero-footprint viewers of diagnostic quality, as well as client-based viewers.  Currently, clients provide a rich feature set, faster manipulation and integration in a reading environment while, zero-footprint viewers provide flexibility of delivery, fast review of compressed data sets to any browser, anytime, anywhere.   These are different tools for  different needs.  You wouldn’t try to use a screwdriver to drive a nail or vice versa.

 

Ultimately, the best solution will blend the advantages of both systems, depending on the needs of the user at a particular time and place.

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

Please let me know what topics you would like to discuss

Kyle@kylehenson.org

That’s not a pencil, it’s a MEDICAL DEVICE!

Three years ago, I was visiting my primary care physician for an annual exam.  My Dr, not fresh out of medical school and had been my family physician for a number of years.  Dr. L did not like computers.  He was writing on my cart in pencil (yes a for real paper chart!).  When I noticed that the pencil was worn down so far that it would only write from one angle and even so was more like a crayon.  I looked at him and said, “you might want to sharpen that pencil.”  He replied, “I can’t, this is a medical device.”  Being the highly technical Imaging person that I am I said, “forgive me Dr, but that is not a medical device, it is just a pencil.”  Slightly exasperated he took off his glasses and looked at me, replying “This is your chart, a medical record.  Obviously, you can see I am making notes and documenting your diagnosis.  You can’t do that with just any writing device, that would be illegal!  I might be audited, you can only make a diagnosis with a medical device!”  Not taking the hint I said, “well at least sharpen it, you can barely write with that.”  Now clearly ticked off Dr. L replied, “were you not listening?!  This pencil is a medical device, if I were to sharpen it, I would have to have a licensed carpenter come in, charging me $400 an hour to sharpen it!  You can’t go messing with a medial device unless you have FDA clearance!”

Sooooooo, maybe there is a hint of sarcasm in my story, but let’s talk about what a medical device is and what the FDA really says.  I was at one time a vendor, and while I was I said many of the same things about my system.  Medical device… can’t patch… blah blah, FDA certification…. I truly believed everything I said.  I had been told that by my company, and I had never read any FDA filings (at the time) so I was retelling what was for me the truth.  Like my former self, many vendors have never read nor do they understand FDA process..

 

The FDA defines a Medical Device as “”…an instrument, apparatus, implement, machine, contrivance, implant, in vitro reagent, or other similar or related article, including a component part, or accessory which is: recognized in the official National Formulary, or the United States Pharmacopoeia, or any supplement to them, intended for use in the diagnosis of disease or other conditions, or in the cure, mitigation, treatment, or prevention of disease, in man or other animals, or intended to affect the structure or any function of the body of man or other animals, and which does not achieve any of its primary intended purposes through chemical action within or on the body of man or other animals and which is not dependent upon being metabolized for the achievement of any of its primary intended purposes.” (Syring, 2018)

 

From that definition we could assume that yes, a pencil is indeed a medical device, or could we?  Did the pencil do anything?  Did it assist in the diagnosis?  Not really, it assisted in recording it.  Similarly, we have to look at the distinction between things that are used in the diagnosis vs what is supporting.  Is a CT or Ultrasound a medical device?  Yes, no question.  What about PACS?  The software is considered a medical device, but the hardware it is running on likely is not.  Let’s examine a real 510(k) letter for a PACS.  By the way if you want to look up the certification for your vendor, which I strongly encourage you can do so on the FDA website.

https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfpmn/pmn.cfm

Back to Vendor X……  “PACS X is medical image and information management software that is intended to receive, transmit, store, archive, retrieve, manage, display, print and process digital medical images, digital medical video and associated patient and medical information.  PACS X includes a suite of standalone, web-enabled software components, and is intended for installation and use with off-the-shelf hardware that meets or exceeds minimum specifications.” (emphasis added)

 

What this means is that the software is a medical device, and when the SOFTWARE is patched it must be tested in accordance with General Principles of Software Validation linked here (Food and Drug Administration (FDA), 2001).  The hardware that it runs on however, does not.  You can run PACS X on any hardware that meets or exceeds specs and it has no impact on the FDA certification whatsoever!  A vendor is well within their rights to provide an approved hardware list, but this is a support issue and not a FDA issue.  This distinction is very important!

 

Because the computer and operating system that run PACS software are not part of the 510(k) certification there is no requirement for the FDA to review security patches.

“Medical device manufacturers can always update a medical device for cybersecurity. In fact, the FDA does not typically need to review changes made to medical devices solely to strengthen cybersecurity.” (Food and Drug Administration, 2018)

There is a one page fact sheet that is very clearly written and I also encourage you to read here.

In summary, your PACS software IS a medical device, however what it RUNS on likely is not.   Especially given security concerns it behooves us all to read the FDA guidance and hold our vendors accountable to make sure that our devices are patched and up to date.  No one wants to report to the CEO or CIO that their system was responsible for a virus or ransomware attack on the enterprise.  Also surprising to me was that for all the secrecy and mystery surrounding medical devices and subsequent maintenance, the FDA website is surprisingly clear and easy to understand.

 

Thank you for reading, please post comments and questions !

Kyle Henson

 

 

References

Food and Drug Administration (FDA). (2001, 02 25). Information for Healthcare Organizations about FDA’s “Guidance for Industry: Cybersecurity for Networked Medical Devices Containing Off-The-Shelf (OTS) Software”. Retrieved from Food and Drug Administration Website: https://www.fda.gov/medicaldevices/deviceregulationandguidance/guidancedocuments/ucm070634.htm

Food and Drug Administration. (2018, 02 02). Information for Healthcare Organizations about FDA’s “Guidance for Industry: Cybersecurity for Networked Medical Devices Containing Off-The-Shelf (OTS) Software”. Retrieved from Food and Drug Administration: https://www.fda.gov/medicaldevices/deviceregulationandguidance/guidancedocuments/ucm070634.htm

Food and Drug Administration. (2018, 02 07). THE FDA’S ROLE IN MEDICAL DEVICE CYBERSECURITY. Retrieved from Food and Drug Administration: https://www.fda.gov/downloads/MedicalDevices/DigitalHealth/UCM544684.pdf

Syring, G. (2018, 02 25). Overview: FDA Regulation of Medical Devices. Retrieved from Quality and Regulatory Assoicats: http://www.qrasupport.com/FDA_MED_DEVICE.html

 

 

 

The DICOM is in the Details! Part 2 the Query Retrieve

 

Given the apparent interest in some of the details about DICOM store transactions, thank you to all who read it!  I thought I would add in a brief description of Query / Retrieve and then next week I will write about my favorite, Storage Commit.

A DICOM Query Retrieve transaction is a fairly simple transaction. First there is a query, and then a retrieve, luckily the standards team didn’t go crazy with the names. The first part is of course the query, which is a C-FIND transaction. In a C-FIND we again have a service class user (SCU) and a service class provider (SCP). The provider is going to be the “server” and the user the “client” or the one making the request. The query can be for a study or for a patient. However, it does not have to be only one. The query could be for “all” patients, or All studies done on a certain date, or if you get a wild hair, all dexa studies completed on Friday the 13th that have a patient who’s first name begins with the letter Q.

No matter what the C-FIND attributes are (specifics of the query) the user will send the query to the SCP (provider) and the provider will then issue a C-FIND response. The response is the list of studies that meet the criteria.  Different systems have built in mechanisms to deal with large C-FIND requests, some will reject the request if it is too broad, others will limit the number of responses to and arbitrary number such as 300, while still others don’t mind at all and simply send back a very long list of matches.

The client or SCU now has a list of studies and may decide to retrieve the studies. The command to retrieve a study is typically not “send me x study” it is often a C-MOVE command. Which roughly translates to “send X study over there” with the there usually being the requester. This is mostly semantical, but interesting to me. The C-MOVE command consists of what study is to be sent and where it is to be sent. The where is an Application Entity or AE title. Once the C-MOVE provider has this information, it then begins a DICOM Store transaction with the AE title requested.  For info on the DICOM Store,

see The DICOM is in the Details!

(Yes, shameless plug for clicks)

One interesting note here, in the C-MOVE command the only destination is the AE title, it does not include the IP address or port! This gets complex because almost every PACS and modality has a standard AE title that the vendor uses for EVERY SINGLE INSTALLATION, I won’t call out a single vendor, because they all do it. This was not a problem back in the day because relatively few systems queried each other, and they were often different vendors. Now however, when you are building an enterprise system like a VNA it is not uncommon at all to have many PACS or CPACS from the same vendor. Which brings AE uniqueness into play.

Some PACS will have the ability to use multiple AE titles so you can simply add a new AE for your VNA to send back to, and not change the modalities. Other PACS will only support one AE title and you may have to reconfigure all modalities sending to it. Last tangential point on Query / Retrieve is that this process of C-FIND and C-MOVE is pretty much what all data migration companies do. They simply do a lot of transactions!

Kyle Henson

Please let me know what topics you would like to discuss

Kyle@kylehenson.org

When a picture ISN’T worth a thousand words, where do reports fit into VNA’s and Enterprise Imaging?

 

In traditional imaging systems like Radiology and Cardiology PACS the report is always with the images. In Radiology, the dictation system sends a copy of the report to PACS via HL7 which is ok since it is text. In cardiology it is either a textual report, or the cardiology system creates the report and therefore has a copy. As we get outside of the walls of those two systems, where does the report really live?

For those that don’t read to the end … the answer is DICOM SR  in your VNA but please keep reading!

In an environment where all users are logged into the EMR and launching images from there, it is not an issue as the EMR is now the system of record for the reports and will have a copy. Now, IMAGINE A WORLD (queue deep commercial voice) where images are sent for reading to various physician groups who are not logged into the EMR.  Reading the newest image is not an issue, but what about priors? In some teleradiology workflows prior reports are faxed, others copy and paste prior reports from the EMR, and still others simply read what is in front of them.

I submit that there is a better way. As we move forward with outsourcing reads, and facilities are divested and acquired regularly it makes no sense whatsoever to not keep reports with the images. The two are intrinsically linked and are important for different reasons as part of the patient record. Luckily there are several mechanisms to resolve this. Surprisingly I don’t see them often implemented.

Let’s start with the low hanging fruit, cardiology. Since most CPACS have reporting modules within the system the report is already with the images before the images are archived and / or sent elsewhere. While I am all for FHIR and emerging solutions I prefer to stick with what I can implement today, now, and yes there are options. The simplest is to do an HL7 export to the EMR. This will provide the text but no images. Often times CPACS will generate a PDF report but that ends up being imported as a separate document into the EMR and not linked. There are actually 3 options to export a content rich report besides emailing the pdf.

The first is to utilize HL7 and the encapsulated document (ED) standard. The standard does exist, and it can be done but I have not seen it nor talked to anyone who has tried. The second is to store the PDF document in the XDS, I am all about standards and a big believer in XDS. The problem is that first you have to HAVE an XDS repository which many don’t, and secondly you need a system to act as the XDS source, which many (most) imaging systems don’t do. There is a very easy answer to this problem and one that has been around for a very long time it just isn’t used.

The easy answer is to DICOM Encapsulate the PDF report and store it with the images as another series. Many CPACS do this natively, it is as simple as clicking a button in the configuration to “archive report with images”.   Why this is not done more often is a mystery to me. This is a very good option for CPACS which commonly creates pdfs as the report product but for other systems that rely more on plain text is the PDF the way to go?

There are several options for textual reports as well. HL7 interfaces between systems is an option but HL7 tends to be more of an all or nothing proposition. Again, XDS offers several opportunities, we stored the text reports as CDA objects in XDS, however this shares some of the previously stated limitations with XDS, namely the lack of adoption so far. Still, there is an old school solution to this problem. The DICOM Structured Report (SR).  By using the DICOM SR one can store the report with the images, any time the images are viewed or sent to another location the report goes with it with no additional steps.

I did this with my VNA from the beginning and it has been a huge success as my EMR Viewer can process the SR and therefore when looking at priors for history the report is available for review without the hospitalist having to go back and forth to the EMR to view the interpretation that goes with the images. Similarly, any time images are requested by another facility or need to be shared for patient care the report is always with the images, either as a DICOM SR or an encapsulated PDF. See that was worth reading to the end wasn’t it?

Kyle Henson

Please let me know what topics you would like to discuss

Kyle@kylehenson.org

The DICOM is in the Details! but how does it work?

Most of us use DICOM every day, we smell it, we live it and we talk about it. However, often the deep dark secured is that we don’t really know how it works. What is a SOP? What is a Transfer syntax? And why do the engineers keep talking about Endians?

To begin with lets quickly review how a DICOM Store occurs, the sending system initiates a transaction. The sending system is the USER of DICOM Store (Service Class User or SCU) and the receiver is the Provider of DICOM Store or the Service Class provider (SCP). The user says I have this study that I want to store. The provider (receiver) says great, here I am. Then the user says I want to send a Breast Tomosynthesis Image.

*nerd alert- The type of image to be sent is defined by the SOP Class, the SOP stands for Service-Object Pair which is the Information Object Definition (image type) and DICOM Service Elements (DICOM Wrapper).   The SOP for Breas Tomo is 1.2.840.10008.5.1.4.1.1.13.1.3, which is in a supplement.

https://www.dicomlibrary.com/dicom/sop/

At this time the provider will reply back with yes, no problem or no, I don’t know that that is. If the answer is yes and the receiver (SCP) supports that SOP (see how you are starting to get the lingo!) it will also send back the list of languages it speaks. We are all pretty familiar by now with the 3 types of compression, uncompressed commonly called DICOM, lossless compressed which is compressed but still ok for reading and lossy compressed in which image data is lost but is much smaller. Each of these along with several others are called in DICOM Speak a transfer syntax.

Once the sender and receiver have agreed on what will be stored, the receiver sends back a list of languages it speaks, or transfer syntaxes. The sender or SCU will then select one of these to send the image. Thus, it is the sender the decides whether or not the image is sent compressed or not. Implicit VR Endian is the default DICOM transfer syntax and therefore supported by ALL vendors.  Because of this, many vendors take the easy road and simply accept the default. This is … OK… within a LAN but when the data is stored or transferred over a WAN compression becomes very important.

https://www.dicomlibrary.com/dicom/transfer-syntax/

Now that SCU and SCP have agreed on what is to be sent and how it will be sent the data transmission goes. The transmission can be at the instance level which refers to individual images or at the study level in which many images are sent on the same association. Once the association is complete the sender may initiate a Storage Commit, which I highly recommend when sending to VNA across a WAN.

Briefly in a storage commit message the sender reaches back out to the provider and sends a list of all individual images that were sent. The Provider then responds back either positively that ALL images were received or negatively in which something wasn’t. In the case of negative the entire study is considered a failure and will be resent, which takes up a lot of your bandwidth.

Please like, share and comment. I would love to know what topics are of interest to the imaging people out there!

Kyle Henson

Please let me know what topics you would like to discuss

Kyle@kylehenson.org

How do you architect your VNA?

 

 

Before you can design your VNA you need to identify what exactly it is that you want to build. Implying that requirements are simply to be the long-term archive for images is about the same as saying I want a building to live in, or build me an office building downtown. While there are many, many requirements and concepts, I would like to focus on two for now. The first is the concept of location, where are the images, where are the consumers and where will the images be stored. The second is how to organize data within your VNA.

It seems somewhat anachronistic to be talking about physical location in a virtual world, but location matters because it effects latency which relates to how fast you can move the data. In a perfect world there are gigabit pipes everywhere with no latency and data moves almost instantaneously. However, in my world there are some pretty slow and saturated networks. So, where are the consumers of imaging data? This is typically the radiologists and referring physicians. These users are likely in relatively close physical proximity to the origin of the images; at least in a metropolitan area, Nighthawk and teleradiology is a different subject altogether. To provide the fastest access to data there should be some amount of images near the consumers. This is typically a local cache or short-term storage (STS) often provided by the primary PACS system. However, in many circumstances VNA is now supplying the EMR image viewer directly in which case there should be some subset of images in close proximity to the EMR servers. Depending on the configuration you may need to setup a component of the VNA to act as that short-term storage locally. This is critical in a VNA first workflow which is part of the “deconstructed PACS” concept. Also important is the location of the data center which may be in the building, across town or across the country.   The size of the cache varies based on workflows and user needs primary diagnostics may require a cache of up to 2 years’ worth of data on site, or none at all. When I say 2 years’ worth I simply mean enough storage to hold all data that was acquired in the last two years.

The second and more interesting idea is how to organize data within your VNA. Each vendor has their own terminology, so I will refer to them as “buckets”. How you put data IN to your VNA greatly effects how you get data OUT of your VNA. As we all know business cycles are cyclical, so there will likely be a period of acquisitions and growth, followed by a period of divestitures. The smart VNA team will plan for both.  The simplest way to organize the data is in one big bucket, hey that’s a VNA right? With all data stored in one bucket, something like the accession number or more likely the study Unique Identifier (UID) which is by definition and standard unique throughout the world, would be how data is separated. To find data in your bucket you need to query for a number of fields, like patient name, DOB study type, or in a perfect world the UID. This is simple to setup, easy to get data in but hard to get data out. The other extreme of the spectrum is to create a bucket for everything. Data can be split into endless buckets, I have herd of some facilities that have one bucket per modality, per hospital, per year. Meaning they have hospital A x-ray 2017, ct 2017, MR 2017, then Hospital B x-ray, ct etc….. This is difficult to get data in, but very easy to find data and get it out.

Why would one separate data? It makes reporting much easier as many VNA’s (and PACS) don’t do the best job of analytics. It is also logical when looking at the facility level. The trick is to expand the view up to an enterprise of say 20-40 hospitals and related imaging centers and the problem becomes more complex and too many buckets becomes unsustainable. Having worked with many enterprises through the years I have settled into the “sweet spot”. Basically, I plan for an eventual divestiture. This is typically not done at the modality level, but at a facility level. No one has ever asked me to separate out and deliver only one modality, but often times an imaging center is bought or sold as is a hospital. This level allows for adequate reporting and tracking but also facilitates the smooth transition during a divesture.

In practical terms I have found that 4 walls define a facility, as does a business relationship. Hospital A may have a woman’s care center in house, an imaging department and an off campus urgent care center (UCC). I would create a VNA bucket for each, as well as each source system. PACS, CPACS, ophiology, surgery and eventually pathology are unique entities that should have separate data, as they will likely be replaced and upgraded on separate schedules. Therefore, they each get their own bucket. That does of course bring up the question of mammography. When there is a separate departmental system for mammography it is often connected into PACS. If there is a workflow reason to store these images into PACS then I would not create a separate VNA bucket.  If there is no reason to then have the mammo system archive to VNA directly.

One last point, is that there is effort and complexity that goes into breaking up imaging streams into separate buckets. This setup cost must be weighed against the benefit of reporting and long term possible divesture. I can confidently say that when you go through the offloading and divesture process you will be very glad you have the data broken out because it makes the process significantly easier. In that environment the facility has already been sold and therefore it is difficult to justify resources to the process. You will want to be able to point the new owner to the data and let them retrieve it having confidence that the data is separated in your VNA such that they can’t see or accidently get to other data.

Kyle Henson

Please let me know what topics you would like to discuss

Kyle@kylehenson.org