The IR Radlex Project: An Interventional Radiology Lexicon—A Collaborative Project of the Radiological Society of North America and the Society of Interventional Radiology

Background 

In 2005, six RadLex organ system committees were formed by the RSNA in collaboration with more than 30 radiology professional and standards organizations, including ACR, Digital Imaging and Communications in Medicine, and Integrating the Healthcare Enterprise. During 2006, each of these committees met twice to discuss and approve anatomic and pathologic terms. As a result of these deliberations, more than 7,500 terms were released publicly in November 2006.

In 2007, six additional committees were recruited, each focusing on a specific imaging modality. These modality committees defined terms to describe the devices, imaging examinations, and procedure steps performed in radiology. This modality effort is called the RadLex Playbook because it is intended to describe the tasks that can be performed in the radiology department— the radiology “playbook”. The Play-book is an initiative complementary to the Uniform Protocols for Imaging in Clinical Trials initiative, which aims to foster the ongoing development of widely acceptable, consistent imaging protocols and quality control procedures across multiple sites and modalities (7). The goal of the Playbook is to ensure that, when a protocol is standardized, manufacturers will harmonize the nomenclature and parameters of their equipment. The interventional radiology (IR) RadLex project is part of RadLex. In January 2007, Dr. Gary Becker and Dr. John Cardella put the IR RadLex project into motion on behalf of the Society of Interventional Radiology. Dr. Sanjoy Kundu chairs the Society of Interventional Radiology (SIR) IR RadLex/lexicon and RSNA IR RadLex committees. Over a 3-month period, an international committee of interventional radiologists was assembled to establish the IR RadLex Committee. During the subsequent 6 months, terms and descriptions were compiled using multiple resources. These included IR textbooks, SIR quality improvement standards documents, and recent research. The IR RadLex project was completed in November 2007 and approved by the SIR Executive Council. Playbook terms are now available on the RadLex Web site, together with a new version of anatomy and pathology terms.

Significant adoption of RadLex is already occurring, including by radiology decision support and reporting vendors, and translations into German, Spanish and Portuguese. There have been more than two dozen RSNA scientific abstracts and exhibits related to RadLex in the past 3 years. RadLex is supported both by the National Institute of Biomedical Imaging and Bio-engineering and by the cancer Biomedical Informatics Grid project, a large National Institutes of Health– sponsored effort to develop unified computing infrastructure for clinical trials.

Lexicon Organization 

To understand the scope of RadLex, it is helpful to review the overall organization of the lexicon.

IR RadLex Terminology 

There has been specific terminology created for the IR RadLex unique to interventional radiology. Table 1 shows example terms describing the preliminary “procedure step”.

Table 1. Example Terms Describing the Preliminary “Procedure Step”

	ISA:	Interventional procedure step
	ATT:	Target anatomic location [DEF: anatomic location of the finding being treated]
		{RadLex anatomic location}
		Finding being treated
		{RadLex finding}
		Interventional procedure anesthesia type
		{RadLex anesthesia type}
		Interventional procedure sedation depth
		{RadLex sedation depth}
		Image guidance modality
		{RadLex imaging modality}

Note.—Key to understanding RadLex text files is as follows: Indentation indicates a parent-child relationship between terms. The three-letter codes at the beginning of line describe the relationship between the parent term and the child term (eg, ISA, child is a type of the parent; ATT, child is an attribute of the parent). These relationships carry over to subsequent lines of the file until a new code appears. The codes in square brackets list additional attributes of terms (eg, DEF, definition; COM, comment). Synonyms are listed after the preferred term on the same line, separated by semicolons. Boldface indicates key terms being defined. Curly brackets indicate possible values of an attribute. Curly brackets containing “RadLex” followed by a term name indicate the value of this attribute can be that term name or any of its offspring in the RadLex tree. The raw IR RadLex files can be viewed on the SIR Web site at http://sirweb.org under the Clinical Practice Guidelines section. The entire RadLex lexicon can be viewed at http://radlex.org.

Sample IR Procedure Using the IR RadLex 

Table 2 shows an example involving use of the IR RadLex in a percutaneous liver biopsy for a focal mass.

Table 2. Sample IR Procedure Using the IR RadLex: Percutaneous Liver Biopsy for a Focal Mass

	Procedure step
	Interventional procedure step
	Target anatomic location
	Liver: right lobe: segment 8
	Finding being treated
	Focal liver mass
	Interventional procedure anesthesia type
	Local anesthetic: 2% xylocaine: 8 mL
	Interventional procedure sedation depth
	Moderate sedation: 2 mg midazolam, 50 μg fentanyl
	Image guidance modality
	US
	Obtain access procedure step
	Organ system access location
	Percutaneous: liver
	Cutaneous access location
	Subcoastal
	Interventional approach access technique
	Transhepatic
	Needle stylet: yes with notch
	Needle Tip type
	Bevel needle tip
	Needle diameter: 18 gauge
	Needle length: 10 cm
	Biopsy procedure step
	Biopsy instrument type core biopsy gun
	Number of samples: 3

Application to IR 

The IR RadLex will enable rich indexing of online teaching materials and clinical data. When procedures are uniformly indexed, clinical and teaching materials are more likely to be found and used by students, trainees, researchers, and radiologists seeking continuing education opportunities. A uniform method of indexing will permit data mining for clinical research and registries, auditing of types of procedures and outcomes, and quality assurance regardless of location or site of practice. Interventional radiologists in different parts of the world will be able to communicate regarding procedures using a common language and vocabulary. The IR RadLex may also facilitate structured IR procedure reporting in the future.

Future Directions 

RadLex has completed the initial development phase, comprising largely term acquisition. However, to make it more useful, additional knowledge must be added to RadLex. During the next few years, RadLex will begin acquiring representative images to provide a more explicit definition of RadLex terms. English definitions will also be provided to reduce potential ambiguity by users of RadLex terms. It will also be important to begin making links from RadLex to related terms in other lexicons. Both the National Library of Medicine and the National Cancer Institute distribute comprehensive thesauri of clinical terms. Both these organizations have indicated preliminary interest in including the new elements of RadLex into their thesauri. The RadLex project will also establish links to the ACR Index. Later this year, the lexicon will be distributed through BioPortal, an effort by the National Center for Biomedical Ontology, to distribute terminology systems like RadLex on the internet (http://www.bioontology.org/ncbo/faces/index.xhtml, http://www.bioontology.org/ncbo/faces/pages/ontology_list.xhtml). BioPortal will provide a set of Web services that will enable developers to create RadLex-enabled applications, such as text indexing, Web search, and terminology-enhanced voice recognition. The IR RadLex will continue to be updated over time, reflecting new techniques and technologies being developed in interventional radiology.