A natural language processing algorithm to extract characteristics of subdural hematoma from head CT reports

  • Peter PruittEmail author
  • Andrew Naidech
  • Jonathan Van Ornam
  • Pierre Borczuk
  • William Thompson
Original Article



Subdural hematoma (SDH) is the most common form of traumatic intracranial hemorrhage, and radiographic characteristics of SDH are predictive of complications and patient outcomes. We created a natural language processing (NLP) algorithm to extract structured data from cranial computed tomography (CT) scan reports for patients with SDH.


CT scan reports from patients with SDH were collected from a single center. All reports were based on cranial CT scan interpretations by board-certified attending radiologists. Reports were then coded by a pair of physicians for four variables: number of SDH, size of midline shift, thickness of largest SDH, and side of largest SDH. Inter-rater reliability was assessed. The annotated reports were divided into training (80%) and test (20%) datasets. Relevant information was extracted from text using a pattern-matching approach, due to the lack of a mention-level gold-standard corpus. Then, the NLP pipeline components were integrated using the Apache Unstructured Information Management Architecture. Output performance was measured as algorithm accuracy compared to the data coded by the two ED physicians.


A total of 643 scans were extracted. The NLP algorithm accuracy was high: 0.84 for side of largest SDH, 0.88 for thickness of largest SDH, and 0.92 for size of midline shift.


A NLP algorithm can structure key data from non-contrast head CT reports with high accuracy. The NLP is a potential tool to detect important radiographic findings from electronic health records, and, potentially, add decision support capabilities.


Subdural hematoma Natural language processing Cranial CT reports Intracranial hemorrhage 


Funding sources

Dr. Pruitt was supported by a National Research Service Award postdoctoral fellow supported by the Agency for Healthcare Research and Quality (AHRQ) T-32 HS 000078 (PI: Jane L. Holl, MD, MPH). AHRQ was not involved in the design or execution of this research. Dr. Pruitt is now supported by a career development award from the Society for Academic Emergency Medicine Foundation.

Author contributions

PP, AN, and WKT conceived of the study and designed the analysis. PB, JO, and PP participated in the abstraction and coding of data. WKT programmed the algorithm. PP performed the data analysis. PP drafted the manuscript and all authors contributed substantially to its revision. PP takes responsibility for the paper as a whole.

Compliance with ethical standards

Conflicts of interest

The authors declare that they have no conflict of interest.


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Copyright information

© American Society of Emergency Radiology 2019

Authors and Affiliations

  1. 1.Department of Emergency MedicineNorthwestern University Feinberg School of MedicineChicagoUSA
  2. 2.Center for Healthcare StudiesNorthwestern University Feinberg School of MedicineChicagoUSA
  3. 3.Department of NeurologyNorthwestern University Feinberg School of MedicineChicagoUSA
  4. 4.Harvard Affiliated Emergency Medicine ResidencyBostonUSA
  5. 5.Department of Emergency MedicineMassachusetts General HospitalBostonUSA
  6. 6.Department of Emergency MedicineHarvard Medical SchoolBostonUSA
  7. 7.Center for Health Information PartnershipsNorthwestern University Feinberg School of MedicineChicagoUSA

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