SNOMED (the Systematized Nomenclature of Medicine) is the preferred coding system within DICOM for anatomy, clinical findings, procedures, pharmaceutical/biologic products (including contrast agents), and other clinical terms.

Note: SNOMED is a registered trademark of the International Health Terminology Standards Development Organisation.

SNOMED has had various versions, including SNOMED International (Version 3), which was issued in 1993 and revised through 1998, SNOMED Reference Terminology, the successor to SNOMED 3 that was published between 1999 and 2001, and SNOMED Clinical Terms, which has been the name since 2002. The coding scheme is fully backward-compatible across SNOMED 3, SNOMED-RT, and SNOMED CT. SNOMED CT introduced a solely numeric set of codes (ConceptID) in addition to the former alphanumeric codes (SnomedID), but all SNOMED terminology concepts have both a numeric and an alphanumeric code.

In previous editions of the DICOM Standard, the following Coding Scheme Designators were used for SNOMED codes in DICOM:

• "99SDM", denoting the provisional SNOMED DICOM Microglossary

• "SNM3", denoting SNOMED International (Version 3)

• “SRT”, originally denoting SNOMED-RT

All uses of SNOMED coded terms in DICOM are now indicated by the Coding Scheme Designator “SRT”, identifying them as SNOMED CT terms using the “SNOMED-RT style” alphanumeric code values, with some exceptions:

• The NM and PET Image IODs in some code sequences require the Coding Scheme Designator “99SDM” as an Enumerated Value (see PS3.3).

• The Mammography View Codes of CID 4014 and CID 4015 may use the Coding Scheme Designator “SNM3” for implementation adherence to regulatory approvals.

Consequently, when a Coding Scheme Designator of “99SDM” or “SNM3” is encountered, it shall be treated as equivalent to “SRT” for the purpose of interpreting the Code Value.

Note: “SRT” as a coding scheme designator is used only in the DICOM Standard. HL7v2 did not standardize a coding scheme designator for SNOMED-RT.

When interoperating with systems that use SNOMED CT codes obtained from a source other than the DICOM Standard, Application Entities may receive Code Sequences with a Coding Scheme Designator of “SNOMED-CT” and a numeric ConceptID code. It is the responsibility of such Application Entities to convert any such codes to the alphanumeric SnomedID with Coding Scheme Designator “SRT” for use in DICOM objects and services.