7.2.2 Units Of Measurement

Context Group 82 is defined to include all units of measurement relevant to DICOM IODs. In the past it was envisaged that an extensible list of pre-coordinated codes would be included in the mapping resource.

DICOM has now adopted the Unified Codes for Units of Measurement (UCUM) standard for all units of measurement. This coding scheme allows for the “construction” of pre-coordinated codes from atomic components.

The specialization of the UCUM standard as it is used in DICOM involves the following rules:

7.2.3 Extension of Context Groups

An Application may extend an Extensible Context Group by adding terms for new concepts. Applications may not substitute other terms of the same concept in the Context Group. Such extension may be made without a change in Context Group Identifier, but with the specification of Context Group Extensions (see PS3.3).

Non-extensible Context Groups shall not be modified in an Application.

Note: The set of concepts in either an Extensible or a Non-extensible Context Group may be changed in subsequent editions of the Standard, in accordance with the procedures of the DICOM Standards Committee.