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Radlex: a lexicon for radiology

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General purpose and services to the end user

RadLex provides a structured vocabulary of terms used in the field of radiology. Currently completed are listings of anatomic terms and "findings", which includes things that can be seen on or inferred from images produced by radiologists. These two sets include a total of about 7500 terms. A list of the terms used to describe the creation of such images, including information about the equipment used and the various imaging sequences performed, will be complete by the end of 2007.

Functionality examples

An example application demonstrating functionality is an image annotation program that reads in RadLex and provides users ability to search for and use particular RadLex terms to associate with images. Users would want to be able to retrieve RadLex terms by name or synonym.

Additional references



Titles of Vocabularies

RadLex: a lexicon for radiology

General characteristics (size, coverage) of the vocabularies

RadLex is a taxonomy currently built predominantly using isa relations, but there are also part-of and other relations (especially for anatomy), and new relations will be added as RadLex expands. Each term has a rich set of metadata fields to include provenance information and terminological data such as synonyms, definition, and related terms from other vocabularies.

Structure of the Vocabulary

The release version of RadLex is at

Each term has metadata, including:

--Term name
--ID number
--parents, and their relation to the term
--children, and their relation to the term
and optionally, any 
--mappings to other vocabularies
--source (a reference publication which includes this term)
--other comments (such as derivation of the term, special or preferred uses of it, etc.)

There are 9 separate hierarchies in the vocabulary: Treatment; Image acquisition, Processing and Display; Modifier; Finding; Anatomic Location; Uncertainty (to be renamed Certainty); Teaching Attribute; Relationship; and Image Quality(as seen in the screenshots above). Each term is given a numerical ID with no inherent semantics. There are currently no relations holding between terms in different hierarchies, though this could be developed in future (e.g. linking of particular Findings to potential Anatomic Locations.)

The relationships used among terms include:

Continuous with  [DEF: Two structures are “continuous with” one another if they are immediately adjacent and physically connected to one another.  This relationship is often used for cavitary and tubular structures, such as the continuity between the left ventricle and the aorta.  This is a reflexive relation.] 
Branch of [DEF: a smaller conduit is a “branch of” a larger conduit if it is one of a group of two or more conduits that continue in the direction of flow where only one conduits had existed before.  It is permissible for one of the continuing conduits to maintain the same name of original conduits.  This relation is often used with arteries.] 
Branch [DEF: the converse relation to “branch of”] 
Tributary of  [DEF: a smaller conduit is a “tributary of” a larger conduit if it is one of a group of two or more vessels that join to form a single conduit in the direction of flow.  This relation is often used with veins. ] 
Tributary [DEF: the converse relation to “tributary of”] 
Part of  [DEF:  one object is “part of” another object if it comprises less than all of the other object.  This relation is often used with solid body parts and organs.] 
Segment of [DEF: one tubular structure is a “segment of” another if it defines a part of that structure divided perpendicular to the axis of the tube.  This relation is often used to define the subparts of tubular structures, such as arteries, veins, and intestines. 
Part [DEF: the converse relation to “part of”]
Segment [DEF: the converse relation to “segment of”] 
Contained_in [DEF: One structure is “contained in” another if the first structure is inside the other.  For example the liver is contained in the abdominal cavity.] 
Contains [DEF: the converse relation to “contained in”] 
Is_a; Type of 
Member of [DEF: One structure is a “member of” a set of structures.  For example, the “liver” is a member of the “set of viscera of abdomen”] 
Member [DEF: the converse relation to “member of”] 
Synonym [DEF: the term is a less-preferred synonym of a preferred term] 

For instance, in Example 3, “nervous system” has a part called “brain”, and “nervous system” contains “nervous system spaces”. The view of the hierarchy itself does not reveal the relationships among the terms; this information is found within the term features, shown in this format on the right-hand side. In this framework, the hierachy is generated from the different relationships amongst terms, using either SPARQL or a custom interface to an application that consumes the terminology.

Language(s) in which the vocabulary is provided

English, with plans to include other languages (e.g., German)

Machine-readable representation of the vocabulary

Protégé and XML version of the vocabulary are available at

Software applications used to create and/or maintain the vocabulary, features lacking for the case


Standards and guidelines considered during the design and construction of the vocabulary

We used basic guidelines from Cimino and Chute, such as ensuring that a term only corresponds to one concept. As we are developing the terminology into a more structured form, with more types of relationships, we are allowing different parents, as long as the relationship type is different. E.g. one ISA parent, one PART-OF parent, etc. We relied on SNOMED and the American College of Radiology Index as a starting point for terminology development.

Management of changes

Potential changes are submitted to the chair of the RadLex Steering Committee of the Radiological Society of North America, who consults with the relevant lexicon development committee. Accepted changes are periodically incorporated into the vocabulary. The first release was made public in November 2006.

Additional references

The vocabulary can be searched and browsed online at

Vocabulary mappings

We are developing a mapping to the corresponding terms/codes in SNOMED (Systematized Nomenclature of Medicine) and the ACR (American College of Radiology) Index.

From a representational point of view, this mapping shall consist of equivalence and specialization links. Later, we expect people to compose atomic terms (post-coordination) to describe composite entities.