DICOM PS3.5 2017d - Data Structures and Encoding

B.2 UUID Derived UID

[ISO/IEC 9834-8] / [ITU-T X.667] defines a method by which a UID may be constructed from the root "2.25." followed by a decimal representation of a Universally Unique Identifier (UUID). That decimal representation treats the 128 bit UUID as an integer, and may thus be up to 39 digits long (leading zeros must be suppressed).

A UUID derived UID may be appropriate for dynamically created UIDs, such as SOP Instance UIDs, but is usually not appropriate for UIDs determined during application software design, such as private SOP Class or Transfer Syntax UIDs, or Implementation Class UIDs.

DICOM PS3.5 2017d - Data Structures and Encoding