What is a DICOM File?

How to Open, Edit, & Convert DICOM Files

Picture of a brain scan
© Peter Dazeley / Photographer's Choice / Getty Images

DICOM is an acronym for Digital Imaging and Communications in Medicine. Files in this format are most likely saved with either a DCM or DCM30 (DICOM 3.0) file extension, but some may not have an extension at all.

DICOM is both a communications protocol and a file format, which means it can store medical information, such as ultrasound and MRI images, along with a patient's information, all in one file.

The format ensures that all the data stays together, as well provides the ability to transfer said information between devices that support the DICOM format.

Note: The DCM extension is also used by the macOS DiskCatalogMaker program as the DiskCatalogMaker Catalog format.

Important: Don't confuse the DICOM format, or a file with a DCM extension, with the DCIM folder that your digital camera, or smartphone app, stores photos in. See Why Are Photos Stored in a DCIM Folder? for more on this.

Open DICOM Files With a Free Viewer

DCM or DCM30 files that you find on a disc or flash drive given to you after a medical procedure can be viewed with the included DICOM viewer software that you'll also find on the disc or drive. Look for a file called setup.exe or similar, or look through any documentation given to you with the data.

If you can't get the DICOM viewer to work, or there wasn't one included with your medical images, the free MicroDicom program is an option.

With it, you can open the X-ray or another medical image directly from the disc, via a ZIP file, or even by having it search through your folders to find the DICOM files. Once one is opened in MicroDicom, you can view its metadata, export it as a JPG, TIF, or another common image file type, and more.

Note: MicroDicom is available for both 32-bit and 64-bit versions of Windows in both an installable and a portable form. See Am I Running a 32-bit or 64-bit Version of Windows? if you're not sure which download link you should choose.

If you'd rather use a web-based tool to open your DICOM files, the free Jack Imaging viewer is one option - just drag your DCM file into the square on the screen to view it. If you've received a file from your doctor that's supposed to have medical images on it, like from an X-ray, this tool will let you view it.

DICOM Library is another free online DICOM viewer you can use and RadiAnt DICOM Viewer is one more downloadable program that opens DICOM files, but it's only an evaluation version of the full program.

DICOM files may also open with IrfanView, Adobe Photoshop, and GIMP.

Tip: If you're still having trouble opening the DICOM file, it might be because it's compressed. You can try renaming the file so it ends in .zip and then uncompressing it with a free file extractor program, like PeaZip or 7-Zip.

macOS DiskCatalogMaker Catalog files that are saved using the DCM extension can be opened using DiskCatalogMaker.

If you find that an application on your PC does try to open the DICOM file but it's the wrong application or if you would rather have another installed program open DICOM files, see my How To Change the Default Program for a Specific File Extension guide for making that change in Windows.

How To Convert a DICOM File

The MicroDicom program I mentioned a few times already can export whatever DICOM file you have to BMP, GIF, JPG, PNG, TIF, or WMF. If there's a series of images, it also supports saving them to a video file in the WMV or AVI format.

Some of the other programs from above that support the DICOM format might also be able to save or export the file to another format, an option that's likely in a File > Save as or Export menu.

More Help With DICOM Files

See Get More Help for information about contacting me on social networks or via email, posting on tech support forums, and more.

Let me know what kinds of problems you're having with opening or using the DICOM file and I'll see what I can do to help.