What Exactly is DICOM?

Posted by P. Varma on Mar 21, 2018 11:00:00 AM

There are so many different formats out there: JPEG, PNG, PDF, MP3, MOV… the list just goes on and on. While these formats might ring a bell, many people are caught off guard by DICOM. What is it? Plain and simple, DICOM stands for Digital Imaging and COmmunications in Medicine. So, if you are trying to figure out what this format is and how it is relevant to you, keep reading.


DICOM is a worldwide standard in medical imaging. It is used to store and transmit medical images. Similar to how you can embed a tag with a JPEG, DICOM allows you to group essential information into data sets. This can include patient ID, date of birth, as well as other pertinent patient identifier information. However, what this format really ensures is that the data is never separated from the image itself.

So why not just use JPEG? Glad you asked. Here’s the thing - JPEG is far inferior to DICOM. For the most part DICOM images are converted and compressed to a JPEG format when exporting (depending on their end use). JPEG files contain a single monochrome (or color) image. They also have no associated meta-data. DICOM files on the other hand, can contain multiple monochrome images along with a rich set of metadata. Such information can be anything from patient information, institution, modality, and more. So while DICOM can support compressed algorithms like that of JPEG; JPEG cannot do the same. Furthermore, in medical imaging you want a sharp image for diagnosis. In the case of JPEG files, you are looking at lossy images not lossless. This means that the image has a potential of blurring sharp lines.

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How to View DICOM

DICOM formatting ensures that all of the metadata associated with the file stays intact. It is the primary reason why this format is preferred when transferring and storing medical imaging between devices supporting DICOM. So how does one go about opening a .dcm file? You need a DICOM viewer. In fact, here’s a word of warning: do not try to rename the extension on such files. It will not change the format. You must have special conversion software to do this.

In order to view your files, you can open them with your PACS. Typically your local or Cloud PACS includes a viewer. If you have a local PACS, the file will be opened on your viewing station. However, if you are using a Cloud solution, the preferred alternative amongst the medical community, you can open your files directly into your browser anytime and anywhere. If, however, you do not have an infrastructure supporting a PACS, you have other options. For instance, you can download a free DICOM viewer.

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A Word of Advice

Not all free open source DICOM viewers are created equal. Maybe were are bias, but we recommend Horos, a free open source DICOM viewer operable on a Mac. The people at Horos truly care about improving medical outcomes. That’s why along with launching Horos Academy (Horos training straight fom the experts), we are pursuing FDA and CE approval in the year of 2018. What’s really awesome about this venture is that even upon becoming diagnostically approved, Horos will remain free - making it the most widely used free open source DICOM viewer in the world. While it's only been around for 3 years, Horos is now used actively in 160 countries with over 100,000 unique users from radiologists to scientists to students.

Final Thought

DICOM is the preferred file format when it comes to medical imaging. It enables all of the pertinent metadata to remain attached to the file without getting lost. Accessing DICOM files is not difficult either. Just open your files into your implemented solution. Or, if you don't have a PACS, try any one of many paid DICOM viewers...or our personal favorite: Horos, the world’s preferred free open source DICOM viewer. It incorporates all of your valued features and tools without the annoying advertisements.

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