SNOMED aka SNOMED-CT (Clinical Terms) is a coding scheme used in DICOM. SNOMED stands for Systematized Nomenclature for Medicine.

Codes or controlled terminology is essential to communicate concepts and entities in a manner that leaves no guessing. Many codes which are used within DICOM, originate from the SNOMED data dictionary. 

If a new code is needed in a DICOM object, first the most common code schemes (particularly SNOMED) are searched to determine if there is a code already available so as not to duplicate efforts. If there is a new code needed, it will be defined as a DICOM (DCM) code in Part 16 of the DICOM standard.

These codes are encoded in a DICOM image. They are always exchanged as a multi-element group or sequence (SQ) containing the coding scheme used to define the code (SNOMED or any other), its code scheme version number, the code itself and its meaning as a text string. This meaning allows a receiver that does not have access to the list of codes to still display the information to a user.