A Lexicon for Uniform Indexing and Retrieval of Radiology Information Resources

1
A Lexicon for UniformIndexing and Retrieval
ofRadiology Information Resources

• June 17, 2009
• Curtis P. Langlotz, MD, PhD

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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• Existing lexicons incomplete or outdated

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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

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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 3709, 1996
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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 3709, 1996
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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 3709, 1996
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NY Cartoon
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Why Are Lexicons Important?

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

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The Goals of the RadLex Project

• June 17, 2009
• Curtis P. Langlotz, MD, PhD

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RadLex

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

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RSNAs 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

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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

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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

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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

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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

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Use Case Reporting Advisor

• DSS suggests features to look for in the image
• DSS lists ranked differential diagnosis

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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

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Medical Lexicons Completeness for Radiology
Percent of imaging terms in lexicon
Bell Greenes, AMIA Proceedings216, 1994
Humphreys et al, JAMIA 4484, 1997.
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ACR Index Demo
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ACR Index Limitations

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

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What is RadLex ?

• Joint effort with professional organizations and
  standards bodies
• ACR, Fleischner, STR, DICOM, NLM
• Harmonize lexicon development efforts
• Unifying framework for concepts and terms
• Common development process
• Harmonize/collaborate
• Result a freely-available resource

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RSNA Organizational Structure
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Collaborative Process
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Desirable Properties of a Lexicon

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

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Organization of the RadLex System

• June 17, 2009
• Curtis P. Langlotz, MD, PhD

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• Lexicon
• Terminology
• Vocabulary
• Dictionary
• Glossary

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The Lexicon Development Process
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Lexicon Development Process (1)
Primary Data Sources
Texts
Lexicon Steering Committee
Draft Lexicon
Informatics
Journal Articles
Imaging
Standards
Existing Lexicons And DBs
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Lexicon Development Process (2)
Final Lexicon
Lexicon Devel. Committee
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What is a RadLex Term?

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

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Term Hierarchies

• 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

• Is-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

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Term Categories

• Examination type
• Patient identifiers
• Clinical history
• Technique
• Observer context
• Level of difficulty
• Exam quality

• Image location
• Anatomic location
• Findings
• Uncertainty
• Conclusions
• Recommendations
• Relationships

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Lexicon Development Approach

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

• Pitfall
• Competitive terms
• Required terms
• Clinical standards
• Reinvent
• Proprietary

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Relationship to Other Lexicons
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Thoracic Lexicon Efforts

• Fleischner Society Glossaries
• NCI Common Data Elements (CDEs)
• NCI Lung Image Database Consortium (LIDC)
• DICOM Chest CAD supplement

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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

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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

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Points for Discussion

• Inaccuracies
• Gaps
• Duplication
• Need for definition
• Helpful sources

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Lexicographer. A writer of dictionaries a
harmless drudge. -Samuel Johnson A Dictionary
of the English Language (1755)
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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
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Lets Get Started!
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Term Categories

• Examination type
• Patient identifiers
• Clinical history
• Technique
• Observer context
• Level of difficulty
• Exam quality

• Image location
• Anatomic location
• Findings
• Uncertainty
• Conclusions
• Recommendations
• Relationships

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RadLex Term CategoryExamination Type

• Radiograph foot
• CT chest
• MRI abdomen
• Ultrasound pelvis
• Fluoro upper GI series

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RadLex Term CategoryPatient Identifiers

• Name
• Medical record number/Subject number
• Age
• Gender
• Ethnicity
• Sociodemographics (e.g., zip code)

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RadLex Term CategoryClinical History

• Reason for exam
• Medical history
• Symptoms
• Medications
• Family history
• Surgical history
• Physical exam findings
• Laboratory values

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RadLex Term CategoryTechnique

• 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

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RadLex Term CategoryObserver Context

• Who viewed the images?
• Display medium
• Window/level information
• Reconstruction algorithm (e.g., surface
  rendering)
• Availability of CAD or decision support

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RadLex Term CategoryDegree of Difficulty

• Layperson
• Medical student
• Junior resident
• Senior resident
• Radiologist
• Sub-specialist

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RadLex Term CategoryImage Quality

• Uninterpretable
• Non-diagnostic
• Limited
• Diagnostic
• Optimal

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RadLex Term CategoryImage Location

• For example
• On the corner of the lateral view
• On series 1, image 5
• On the post contrast images

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RadLex Term CategoryAnatomic Location

• For example
• The left upper lobe
• The trachea
• The right costophrenic angle

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RadLex Term CategoryFinding

• Visual features
• Anatomical derangements
• Pathologic processes
• Diseases
• Syndromes

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RadLex Term CategoryUncertainty

• Definitely not
• Probably not
• Possibly not
• Uncertain
• Possibly
• Probably
• Definitely

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RadLex Term CategoryConclusion

• 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)

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RadLex Term CategoryRecommendation

• 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

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RadLex Term CategoryRelationships

• 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)