A Lexicon for UniformIndexing and Retrieval ofRadiology Information Resources

April 12, 2023

Curtis P. Langlotz, MD, PhD

Motivations for a Unifying Medical Imaging Lexicon

Tower of Babel Fragmented educational resources for

imaging Irreconcilable research results Suboptimal clinical communication Existing lexicons incomplete or outdated

Benefits of a Unified Imaging Lexicon:

Automatic indexing and retrieval of teaching files

Comparison or unification of disparate research databases

Point and click “structured” reporting systems Literature searches tailored to specific

imaging examinations or patients

Content and Clarity of Radiologists’ Reports

822 Medicare inpatients from 297 hospitals Admission diagnoses: pneumonia, CHF, MI 14 different terms for interstitial edema/infiltrate 23 terms suggesting presence of an abnormality 30 terms for expressing uncertainty

Sobel et al, Acad Radiol 3:709, 1996

Alternative Terms forInterstitial Edema/Infiltrate acute interstitial change edema along markings horizontal linear stranding increase in interstitial

markings Kerley B lines linear parenchymal change septal fluid

interstitial disease interstitial process interstitial changes interstitial prominence fluid congestion peribronchial cuffing perivascular edema vessel type infiltrate

Sobel et al, Acad Radiol 3:709, 1996

Alternative Terms for Presence of an Abnormality appears to be are a bit believe to be compatible with consistent with definite due to evidence for first consideration given to

indicating most likely presumably representing representing seems to be significant somewhat suspect thought to be

Sobel et al, Acad Radiol 3:709, 1996

NY Cartoon

Why Are Lexicons Important?

Donald Harrington, M.D.Professor and Chair, Department of Radiology,State University of New York-Stony Brook

The Goals of the RadLex Project

April 12, 2023

Curtis P. Langlotz, MD, PhD

RadLex

RadLex hypothetical use cases Origins: MIRC and the ACR Index Motivations: incomplete existing lexicons RadLex organizational structure

RSNA’s Medical Image Resource Center (MIRC) Sharing of images and information for

education, research and clinical practice Originally conceived as a central point of

storage (teaching file archive) Now a community of teaching files linked

through a common index Searchable via the Internet

Use Case: Teaching File Creator

Radiologist is reading an interesting case Radiologist selects case for teaching file Radiologist assigns RadLex terms to the case Radiologist makes the case publicly available All radiologists can now search for the case on

the Internet using MIRC and RadLex

Use Case: Information Seeker

Radiologist seeks optimal follow up interval for nodule on hi-res chest CT

Enters RadLex terms describing nodule and clinical history

Receives web page listing links to relevant information

Use Case: Information Seeker

Web page listing relevant: MedLine citations RSNA meeting content (refresher courses, scientific

abstracts) RSNA full-text journal articles MIRC teaching files Professional standards Relevant billing codes

Use Case: Reporting Advisor

Radiologist is using an automated reporting system to report a case

Decision support system is running in the background

Decision support system has been tracking RadLex term co-occurrence over time

Radiologist describes a lung cancer on chest X-ray using RadLex terms

Use Case: Reporting Advisor

DSS suggests features to look for in the image

DSS lists ranked differential diagnosis

Medical Lexicons for Radiology

UMLS (National Library of Medicine) SNOMED-RT (College of American

Pathology) Index for Radiological Diagnoses (ACR) NCI Common Data Elements (CDEs) Subspecialty lexicons: ACR BI-RADSTM,

ASSR-intervertebral disks, Fleischner, ... Coding schemes: ICD, CPT, LOINC

Medical Lexicons: Completeness for Radiology

0%

20%

40%

60%

80%

100%

SNOMED UMLS ACR Index LSVT

Percent of imaging terms in lexicon:

Bell & Greenes, AMIA Proceedings:216, 1994Humphreys et al, JAMIA 4:484, 1997.

ACR Index Demo

ACR Index Limitations

Two “fields”: Anatomy, Pathology Semantics embedded in identifiers Designed for “off-line” teaching files Coarse hierarchy Static categories for findings

What is RadLex ?

Joint effort with professional organizations and standards bodiesACR, Fleischner, STR, DICOM, NLM

Harmonize lexicon development effortsUnifying framework for concepts and termsCommon development processHarmonize/collaborate

Result: a freely-available resource

RSNA Organizational Structure

RadLex

Steering

Committee

RadLex

Thoracic Lexicon

Devel. Committee

Other RadLex

Lexicon Devel.

Committees

…

Collaborative ProcessTask RSNA Partner

Common lexicon framework X

Common development process X

Select committee members X X

Create draft lexicons X

Provide informatics tools X

Support meetings, conf. calls X

Review and refine lexicons X X

Establish on-line availability X

Disseminate new lexicon X X

Liaison to standards, govt. orgs. X

Desirable Properties of a Lexicon

Donald Harrington, M.D.Professor and Chair, Department of Radiology,State University of New York-Stony Brook

Organization of the RadLex System

April 12, 2023

Curtis P. Langlotz, MD, PhD

LexiconTerminologyVocabularyDictionaryGlossary

The Lexicon Development Process

Lexicon Development Process (1)

Texts

JournalArticles

ExistingLexiconsAnd DBs

Informatics

Imaging

Standards

Lexicon Steering Committee

Primary Data Sources

Draft Lexicon

Lexicon Development Process (2)

Final Lexicon

Lexicon Devel.Committee

Web-based resource

You are here.

What is a RadLex Term?

Unique concept Unique numeric ID Name Definition Sample image(s) Source(s) Links to related terms/lexicons

Term HierarchiesIs-a (e.g., Finding) pneumonia

bacterial pneumonia aerobic bacterial

pneumonia gram-positive aerobic

bacterial pneumonia gram-negative aerobic

bacterial pneumonia anaerobic bacterial

pneumonia mycobacterial pneumonia

tuberculosis primary tuberculosis post-primary

tuberculosis non-tuberculous

mycobacterial pneumonia …

Part-of (e.g., Anatomy) lungs

left lung left upper lobe of lung

superior division of the left upper lobe

anterior segment of the left upper lobe

apicoposterior segment of the left upper lobe

lingula inferior segment

of the lingula superior

segment of the lingula

left lower lobe of the lung …

Term Categories

1. Examination type

2. Patient identifiers

3. Clinical history

4. Technique

5. Observer context

6. Level of difficulty

7. Exam quality

8. Image location

9. Anatomic location

10. Findings

11. Uncertainty

12. Conclusions

13. Recommendations

14. Relationships

Lexicon Development Approach

Solution Synonymous terms Common terms Standard descriptors Adopt and link Publicly available

Pitfall Competitive terms Required terms Clinical standards Reinvent Proprietary

Relationship to Other Lexicons

ACR

Index

SNOMED CPT4

ICD-9-CM

RadLex

UMLS

Thesaurus

Thoracic Lexicon Efforts

Fleischner Society Glossaries NCI Common Data Elements (CDEs) NCI Lung Image Database Consortium

(LIDC) DICOM Chest CAD supplement

Fleischner Glossaries

Imaging features unique to radiology Excellent definitions No categories, hierarchies or other

framework No unique identifiers Not available in electronic form for indexing

RadLex-Fleischner Process

Use Fleischner glossary terms and definitions when possible

Note when the Fleischner glossary is a source of a RadLex term

Assign a RadLex unique identifier to each term

Place each Term in a RadLex category

Points for Discussion

Inaccuracies Gaps Duplication Need for definition Helpful sources

Lexicographer. A writer of dictionaries; a harmless drudge.

-Samuel JohnsonA Dictionary of the English Language (1755)

The Augean Stables

For the fifth labor, Eurystheus ordered Hercules to clean up King Augeas' stables. Now King Augeas owned more cattle than anyone in Greece. Some say that he was a son of one of the great gods, and others that he was a son of a mortal; whosever son he was, Augeas was very rich, and he had many herds of cows, bulls, goats, sheep and horses. Hercules knew this job would mean getting dirty and smelly, but sometimes even a hero has to do these things.

-The Perseus Project; www.perseus.tufts.edu

Let’s Get Started!

Term Categories

1. Examination type

2. Patient identifiers

3. Clinical history

4. Technique

5. Observer context

6. Level of difficulty

7. Exam quality

8. Image location

9. Anatomic location

10. Findings

11. Uncertainty

12. Conclusions

13. Recommendations

14. Relationships

RadLex Term Category:Examination Type Radiograph foot CT chest MRI abdomen Ultrasound pelvis Fluoro upper GI

series

RadLex Term Category:Patient Identifiers Name Medical record number/Subject number Age Gender Ethnicity Sociodemographics (e.g., zip code)

RadLex Term Category:Clinical History Reason for exam Medical history Symptoms Medications Family history Surgical history Physical exam findings Laboratory values

RadLex Term Category:Technique Equipment (e.g. 1.5T MRI) Imaging parameters (e.g., image

weighting) Patient positioning Date/time images created Field of view Contrast agent administered, if any

RadLex Term Category:Observer Context Who viewed the images? Display medium Window/level information Reconstruction algorithm (e.g., surface

rendering) Availability of CAD or decision support

RadLex Term Category:Degree of Difficulty Layperson Medical student Junior resident Senior resident Radiologist Sub-specialist

RadLex Term Category:Image Quality Uninterpretable Non-diagnostic Limited Diagnostic Optimal

RadLex Term Category:Image Location For example

On the corner of the lateral viewOn series #1, image #5On the post contrast images

RadLex Term Category:Anatomic Location For example:

The left upper lobeThe tracheaThe right costophrenic angle

RadLex Term Category:Finding Visual features Anatomical derangements Pathologic processes Diseases Syndromes

RadLex Term Category:Uncertainty Definitely not Probably not Possibly not Uncertain Possibly Probably Definitely

RadLex Term Category:Conclusion Normal No clinically significant findings Expected findings for patient demographics

(e.g., normal for age) Probably no clinically significant findings

(confirmatory future follow-up needed) Clinically significant findings (workup should

continue) Urgent clinically significant findings (definitive

therapy required)

RadLex Term Category:Recommendation Comparison to prior exams Correlation with other patient information, such

as laboratory tests, surgical and medical history Follow up imaging, including the type of imaging

examination and the time interval Tissue sampling Definitive therapy, such as surgical excision or

medical therapy

RadLex Term Category:Relationships Spatial

(e.g., the tumor arises from the upper pole) Logical

(e.g., pneumonia and congestive heart failure) Causal

(e.g., the increased signal is due to a brain tumor)