7 DCMR Context Group Specifications

Context Groups specify Value Set restrictions for Code Value (0008,0100) and Code Meaning (0008,0104) of Code Sequence Attributes for given functional or operational contexts. This Section specifies the semantics of DCMR Context Group Tables.

7.1 Context group Table field definition

Context Groups are described using tables of the following form (optional columns are shown with italic column titles):

Context ID <#><Context Group Name>Type: (Non-)Extensible Version: <yyyymmdd>

Coding Scheme Designator Coding Scheme Version Code Value Code Meaning <Reference Terminology> Equivalent Value

A row of a Context Group table specifies one coded concept. Each Context Group table is named by a title and identified by a CID number and version.

The columns of the tables consist of:

In those cases where it is necessary, Coding Scheme Version (0008,0103) may also be specified. This column may be absent if Coding Scheme Version is not required for any of the coded concepts in the Context Group.

The value specified in the Code Meaning field is an acceptable value for the specified code value, but does not preclude the use of other synonymous text in the same or other language.

Note: Some coding schemes such as LOINC do not specify the equivalent of a Code Meaning.

If further description of the concept represented by the code is required in the DCMR (rather than referring to an external coding scheme), it is included in a separate table.

An optional column may provide an informative mapping from the coded concepts of the Context Group to a reference terminology specified in the column heading.

A Context Group may alternatively be defined by narrative reference to an externally defined coding scheme.

Note: See for instance CID 82.

7.2 Special Conventions for context group tables

7.2.1 Include Context Group

The ‘Include Context Group’ macro is a concise mechanism for including (by-reference) all of the rows of a specified Context Group in the invoking Context Group, effectively substituting the specified Context Group for the row where the macro is invoked. If an ‘Include Context Group’ is specified, it shall be specified in the Concept Name column of a Context Group Table. Table 7.2.1-1 specifies the syntax of the ‘Include Context Group macro. Inclusion may be nested, in that included Context Groups may themselves include other Context Groups. This gives rise to the possibility of circular inclusion and multiple inclusion, in which case the Context Group shall consist of the transitive closure of the set of all coded concepts within the included Context Groups.

Note: For example, it is reasonable to have the following definitions for context groups:

Context ID 1, includes Context IDs 2 and 3

Context ID 2, includes Context IDs 4 and 5

Context ID 3, includes Context IDs 5 and 6

Context ID 4 contains a, b, c

Context ID 5 contains e, f, g

Context ID 6 contains a, h, i

The contents of Context ID 1 will be a, b, c, e, f, g, h, i.

Table 7.2.1-1Include Context Group Macro

Coding Scheme Designator (0008,0102) Code Value (0008,0100) Code Meaning (0008,0104)
Include CID nnn

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.