.dcm File Extension
.dcm file contains, which DICOM viewers open it, how Poly supports it, and how to share or convert it safely. File extension details for .dcm
Storage Only| File type | DICOM medical data file |
|---|---|
| MIME type | |
| Encoding | Binary DICOM PS3.10 file with structured metadata and an encoded data set |
| Operating systems | Windows, macOS, Linux |
| Opens with | 3D Slicer, OsiriX MD, DICOM workstations |
| Poly support | Yes. Poly stores, syncs, shares, versions, and downloads DCM files. |
| Indexed by Poly | Name only. DICOM metadata, reports, frames, and pixels are not indexed. |
| Preview in Poly | No. Download the file to open it in a DICOM viewer. |
| Poly agent | No. The Poly agent cannot read the DICOM object's contents. |
What kind of file is a .dcm?
A .dcm file usually contains one DICOM object, such as a CT, MRI, ultrasound, or X-ray instance. DICOM can also represent structured reports, waveforms, radiotherapy plans, and other clinical objects, so a DCM file is not necessarily a single ordinary image. It normally uses the application/dicom MIME type.1
A standard DICOM PS3.10 file has a 128-byte preamble followed by the ASCII characters DICM at byte offset 128. File metadata then identifies the object and the transfer syntax used to encode its data.2 The signature is a useful check, but software still needs to parse the file. A .dcm filename alone does not prove that its contents are valid DICOM.
.dcm file to .jpg does not extract or convert its image. DICOM may combine clinical metadata with uncompressed pixels or pixels encoded using JPEG, JPEG 2000, or another transfer syntax.How do I open a .dcm on my computer?
Use a DICOM-aware viewer rather than a general photo app:
- Windows, macOS, or Linux: 3D Slicer can import DICOM files into its DICOM database and load supported objects.3
- macOS: OsiriX MD provides DICOM database management and 2D, 3D, and 4D medical-image viewing.4
- Clinical systems: A PACS workstation or viewer supplied by a healthcare provider may best preserve series order, presentation states, measurements, and study context.
Import the complete folder when possible. An exam commonly contains many DCM instances grouped into studies and series, and opening one file may show only one slice. Keep any DICOMDIR file with the directory structure it indexes.
Poly support for .dcm
Poly safely stores, syncs, shares, versions, and downloads DCM files. It recognizes the extension and makes the file findable by name and ordinary file properties.
Poly does not currently parse DICOM tags, reports, transfer syntaxes, frames, or pixel data. It therefore does not generate a thumbnail, offer an in-app medical viewer, index clinical contents, or make those contents available to the Poly agent. Download the original and open it in a trusted DICOM application.
History of .dcm
The American College of Radiology and National Electrical Manufacturers Association formed a joint committee in 1983 to improve interoperability between medical-imaging systems. ACR-NEMA 1.0 followed in 1985 and version 2.0 in 1988. A major 1993 revision adopted the name DICOM and added network communication, offline file exchange, and formal conformance statements.6
The .dcm convention was later recorded in the application/dicom media-type registration. RFC 3240, published in 2002, recommends .dcm for DICOM files saved to disk, except for the specially named DICOMDIR index.1
Working with .dcm and alternatives
Choose an export based on what the recipient needs:
| Format | Best use | What is lost or changed |
|---|---|---|
DICOM .dcm | Clinical exchange and preserving the complete object | Requires DICOM-aware software |
| PNG or TIFF | A lossless rendered frame | Clinical metadata, series relationships, and original pixel interpretation |
| JPEG | A small display-ready reference image | Metadata and possibly image detail or bit depth |
| NIfTI or NRRD | Volumetric analysis | DICOM's metadata model and per-instance organization |
Export through a DICOM application instead of changing the filename. Keep the original study when fidelity, provenance, or later clinical use matters, and verify orientation, spacing, windowing, and de-identification in the destination workflow.
Footnotes
- Internet Assigned Numbers Authority. application/dicom Media Type Registration. The registration specifies binary encoding, the
DICMsignature, privacy considerations, and the recommended.dcmextension. ↩ ↩2 - DICOM Standards Committee. DICOM PS3.10: Media Storage and File Format for Media Interchange. Section 7 defines the preamble, prefix, file meta information, and encapsulated data set. ↩
- 3D Slicer Project. Data Loading and Saving. The guide documents DICOM database import and loading. ↩
- Pixmeo. OsiriX MD DICOM Viewer. The product documentation describes DICOM database and multidimensional viewing support. ↩
- DICOM Standards Committee. DICOM PS3.15: Security and System Management Profiles. Annex E defines attribute confidentiality profiles and de-identification options. ↩
- DICOM Standards Committee. DICOM PS3.1, Section 1.3: History. The official history covers ACR-NEMA and the 1993 DICOM revision. ↩