DICOMDIR

The index file on a DICOM CD or USB that catalogues the studies, series, and images on the medium.

A DICOMDIR is the index file of a DICOM file set, the collection of files written to a CD, DVD or USB drive. It sits at the root of the medium and lists every patient, study, series and image on it, together with the path to each file. A viewer reads it to show what is on the disc without opening every file. Importing or cleaning up a patient CD usually starts from its DICOMDIR.

What is inside a DICOMDIR

A DICOMDIR is itself a DICOM file, of the Media Storage Directory Storage SOP Class defined in DICOM PS3.10 and PS3.3. Its Directory Record Sequence (0004,1220) holds a tree of records, one level per item:

• PATIENT records carry the patient’s name and ID.
• STUDY records carry the study date, time, description and Study Instance UID.
• SERIES records carry the modality, series number and Series Instance UID.
• IMAGE records, or other leaf types such as SR DOCUMENT, carry the instance number and the Referenced File ID (0004,1500), which is the path to the file.

Each record points to its next sibling and its first child by byte offset within the DICOMDIR. The file also has a File-set ID (0004,1130) that names the whole set.

PS3.10 limits each part of a file path to eight characters, using only uppercase letters, digits and the underscore. That is why the files on a patient CD have names like DICOM/0000A1B2/00000001 with no extension.

Why a disc may not open without it

Viewers that follow the standard read the DICOMDIR first and show the studies it lists. If the DICOMDIR is missing, damaged, or points to paths that do not exist, some viewers show an empty disc even though the image files are there. Others can scan the folder and read the files directly.

Open a DICOMDIR in dcmage

Click Open folder… on the start screen and choose the folder that holds the DICOMDIR. In the Mac app you can also use File → Open Folder….

• In the Mac app, the DICOMDIR must be at the top level of the folder you choose. dcmage loads the files it references. If the DICOMDIR cannot be parsed, loading stops with an error.
• In the browser, dcmage looks for a DICOMDIR anywhere in the chosen folder and matches the paths it lists without regard to case. If the DICOMDIR cannot be read or none of its paths match, dcmage loads the .dcm files in the folder instead.

dcmage reads the records in sequence order and loads every record that has a Referenced File ID. Once the files are loaded, you can review the studies in the Files tab, edit tags, or de-identify them.

To export loaded files as a media set with its own DICOMDIR, see DICOMDIR generation.