Is my EMR/EHR system a PACS system? And what’s DICOM?

A part of healthcare mandate in recent years is mandatory EMR system. EMR and PACS along with EHR and DICOM comparisons are on top of confusing topics. EMR or EHR stands for Electronic Medical Record (EMR) or Electronic Health Record system (EHR). One of common scenario I run into is where customer says they have PACS system when they only have EMR system. And by the way, what’s DICOM? and RIS? How about MWL? In this article, we’ll go over each term in plain English with examples + share my original diagram to finally put an end to this confusion! We’ll also address basic differences of these systems to help you understand the difference to make an informed decision. (Or at least resolve your curiosity)

PACS system illustration

PACS system illustration in its simplest form I can come up with

If you look at image above, this will give you a basic guideline of how you should think of this topic. And to be honest, there are few more things that can be added to this illustration like HL7, HIS and few other things. But in most clinic settings, you probably won’t see those so I’m limiting this article to what we can expect in ‘normal office/clinic settings’. To help understand the illustration, Circles are Systems/Software, Rectangle is language, Triangle is sub-system, and arrows are Bridge as noted. And keep in mind that I’m intentionally not going into details on each system on this article as goal of this article is to provide summary and basic understanding of functions and difference of all systems. (otherwise this article will never end)

First of all, DICOM is NOT a system. (hence it has different shape in illustration) It’s an international standard language that medical communities use to protect medical images and patient information in a system where only parties with sufficient permission can view and edit. (versus JPG) If you noticed DICOM is on top of all four circles which represents system/software because DICOM can be a connecting factor of all those systems. Just think of DICOM as secret language that only ‘licensed’ system/people can speak, like Latin or chicken scratches.


EMR system is an easy one. It’s your old style paper chart in a computer, aka E-Chart.
EHR is bigger, more comprehensive system that includes EMR. EHR isn’t just record of charts of a patient but it’s designed to contain pretty much all information in regards to health history of a patient. That’s why EHR includes EMR in the illustration.


PACS stands for Picture Archiving and Communication System. PACS system in short is a secure medical image storage system. PACS system also features advanced options and powerful tools to manipulate images for annotations. While most non-hospital clinics are not required to have PACS, terms like PACS and DICOM will often come out when discussing modality (equipment) communication or EMR/EHR compatibilities.
RIS stands for Radiology Information System. RIS is used to order exam of a patient, scheduling and reporting of system. PACS and RIS are usually used together since they go hand in hand where one takes care of ordering and information while the other manages images.
MWL is a sub-component of RIS system but sometimes can be operated semi-independently or directly with PACS. Modality Work List (MWL) manages communications between RIS/PACS and different imaging devices. (modalities)


Here’s an example of PACS/RIS/MWL at work: A family doctor makes an order for CT scan. He inputs that via RIS web portal. When patient goes to a CT center or hospital, receptionist will pull the order via RIS system and send the information to MWL. CT technician at his station gets notified by MWL system and scans the patient according to the instruction provided in MWL system. Once completed, MWL will notify RIS system that study has been completed, updating status to: scanned or pending annotation. MWL will also notify PACS system that image is ready. PACS system, according to its pre-configured schedule pulls information and images into PACS server/central storage. RIS/PACS system then alerts radiologist that image is ready for annotation. Radiologists uses PACS system to manipulate and view the image, making his notes via PACS/RIS system. (remember, these two systems are very closely linked) Usually radiologist will write his notes on images via PACS system and full report on RIS system but that’s depends on personal/organization workflow. Once completed, RIS system will update status to: study complete and notify family doctor who originally placed the order for review.

Simply put (in a long paragraph), this is how these system will work with each other.

Common confusions on these systems/terms come from use of word DICOM. You’ll often hear a sales rep telling you that your ‘EMR/EHR software has DICOM’ or ‘can work like PACS because it has DICOM’. And if you remember, DICOM = PACS, right? If you said yes, you didn’t read my article carefully. It’s ok, I know it’s a long article with lots of confusing terms over and over. Imagine someone argues that because he can write like doctors (chicken scratch), he is a doctor. Saying DICOM = PACS is exactly same argument. When someone says your EMR system has DICOM, they’re either shortening the term to help you understand (but increasing confusion) or they simply don’t understand the term either. Correct term that should be used is ‘Your system (EMR/EHR) comes with DICOM output or DICOM send or even DICOM client.

PACS system illustration

Click here for a full sized illustration

When you have a DICOM send/output (feature), that means you can send your images to a PACS system. Remember, PACS system is by default a secure system. And in order to maintain that security, it will not accept any public images (jpg, png, gif, whatever you can open with regular pc without special software). Many modalities or EMR systems comes with DICOM output to be in compliance with a PACS system, if you already have one. Keyword here is if you already have one. I often get customers who purchase a modality or EMR system with DICOM out, and they tell people that they have a PACS system. Then I’d get calls from technicians who wants to connect their equipment to ‘Customer’s PACS system’ that only has DICOM out. Do you see the problem here?

You cannot create a working system using two programs that only have DICOM send.

Given the length of the article and depth, I think this is a good pause point before this gets too long. If I get the request to explain any specific area of this article further, I’ll be happy to create follow-up articles going in-depth on any of these topics with lots and lots of real life examples and some of my natural sarcastic responses. So feel free to share your thoughts in comments below!

Please remember that this article is simplified version of summary without going into any terminology details or technical details intentionally to help understanding. Let me know if this helped! :)


Notify of

Oldest Most Voted
Inline Feedbacks
View all comments

Thanks. It was both interesting and useful