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File-opening guide

A .dcm file shows as unknown on iPhone: how to open it

An unknown-file icon or missing preview in iPhone Files does not establish that a .dcm file is broken. Save the original and import it through Ossidex using + then Files / ZIP, or choose Folder for a multi-file examination.

By the Ossidex team · How we write and check these pages · Updated

Download on the App StoreFree to download · iPhone & iPad · iOS 17+

Check what was actually saved

What you haveWhat it means
One .dcm attachmentCould be one image or a multi-frame object. Its extension does not tell you whether the examination is complete.
Many .dcm filesUsually need to be imported together to assemble their series. Do not select only the first attachment.
A web page renamed .dcmStill a web page. Return to the portal and download the image export.

How to open the images

  1. Save the original attachment. Use the sending app’s share or save action to keep the file in Files. Wait for any cloud download to finish before importing.
  2. Import from inside Ossidex. Tap +, then Files / ZIP, and select the saved DCM. This avoids relying on a preview or on Ossidex appearing in another app’s share menu.
  3. Include the rest of the series. For a folder of slices, use Folder. Ask for a complete ZIP if the sender shared only one file from a larger series.
  4. Check the imported examination. Open the study, select the intended series and scroll through its images. Compare the examination date and series with the clinic’s export. An image appearing on screen is not proof that every series arrived.

What to check if it still does not open

If Ossidex rejects the file too, record its message rather than treating “unknown” in Files as the diagnosis. The file may be incomplete, use an unsupported encoding, or be a DICOM object without displayable image pixels.

Renaming to JPG does not convert medical pixels to a photograph. Keep the DCM for the study; request or export a separate rendered image only when an ordinary picture is what the recipient needs.

Viewer options and format limits

On a Mac, open the browser viewer and choose Open folder for the complete DICOM folder or Open files for a ZIP. Browser format and memory limits differ from the iPhone/iPad app; a successful import does not establish that the examination is complete.

See the matching format or export guide and tested samples and compatibility limits. Ossidex is a viewer and planning aid, not a diagnostic device.

Frequently asked questions

Why does Files not show a thumbnail?

A file preview depends on the app handling that format. A missing preview is not a test of whether the DICOM pixels are intact.

Do I need every DCM file?

For a multi-file series, keep every slice. A single multi-frame DICOM file can contain a volume, so ask the sender which export you received.

Sources

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