Reference
DICOMDIR
The index file on a DICOM CD or USB that catalogues the studies, series, and images on the medium.
A DICOMDIR is a single index file at the root of a patient CD/USB that lists every study, series, and image on the medium and where each file sits — so a viewer can browse the disc without scanning every file. Importing or cleaning up a patient CD usually starts from its DICOMDIR.