DICOMDIR is file that is used when software saves DICOM file to external storage device such as CD/DVD, USB flash drive, etc.
DICOMDIR records patient and examination information, and others as DICOM tags of tree structure.
And it takes on a role of simple database.
By using DICOMDIR file, it is not necessary to build its own index with scanning the whole file system.
So its performance and usability will be significantly improved.
The name of DICOMDIR file is "DICOMDIR", and it does not have any extension.