title: Semi-automated scoring of pulmonary emphysema from X-ray CT: trainee reproducibility and accuracy.
abstract: OBJECTIVE
  We developed a semi-automated tool to quantify emphysema from thoracic X-ray multi-detector (64-slice) computed tomography (CT) for training purposes and multi-reader studies.
  
  
  METHODS
  Thoracic X-ray CT was acquired in 93 ex-smokers, who were evaluated by six trainees with little or no expertise (trainees) and a single experienced thoracic radiologist (expert). A graphic user interface (GUI) was developed for emphysema quantification based on the percentile of lung where a score of 0=no abnormalities, 1=1-25%, 2=26-50%, 3=51-75% and 4=76-100% for each lung side/slice. Trainees blinded to subject characteristics scored randomized images twice; accuracy was determined by comparison to expert scores, density histogram 15th percentile (HU 15), relative area at -950 HU (RA(950)), low attenuation clusters at -950 HU (LAC(950)), -856 HU (LAC(856)) and the diffusing capacity for carbon monoxide (DL(CO%pred)). Intra- and inter-observer reproducibility was evaluated using coefficients-of-variation (COV), intra-class (ICC) and Pearson correlations.
  
  
  RESULTS
  Trainee-expert correlations were significant (r=0.85-0.97, p<0.0001) and a significant trainee bias (0.15 ± 0.22) was observed. Emphysema score was correlated with RA(950) (r=0.88, p<0.0001), HU 15 (r=-0.77, p<0.0001), LAC(950) (r=0.76, p<0.0001), LAC(856) (r=0.74, p=0.0001) and DLCO%pred (r=-0.71, p<0.0001). Intra-observer reproducibility (COV=4-27%; ICC=0.75-0.94) was moderate to high for trainees; intra- and inter-observer COV were negatively and non-linearly correlated with emphysema score.
  
  
  CONCLUSIONS
  We developed a GUI for rapid and interactive emphysema scoring that allows for comparison of multiple readers with clinical and radiological standards.
authors: Imaging Research Laboratories, Robarts Research Institute, London, Canada; Graduate Program in Biomedical Engineering. Electronic address: aowrangi@robarts.ca.
authors: Amir M
authors: AM
authors: Owrangi
authors: Brandon
authors: B
authors: Entwistle
authors: Andrew
authors: A
authors: Lu
authors: Jack
authors: J
authors: Chiu
authors: Nabil
authors: N
authors: Hussain
authors: Roya
authors: R
authors: Etemad-Rezai
authors: Grace
authors: G
authors: Parraga
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D009864:Ontario / Q000453:epidemiology; D010363:Pattern Recognition, Automated / Q000379:methods* / Q000706:statistics & numerical data; D015995:Prevalence; D011361:Professional Competence / Q000706:statistics & numerical data*; D011656:Pulmonary Emphysema / Q000000981:diagnostic imaging* / Q000453:epidemiology; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods* / Q000706:statistics & numerical data*; D014584:User-Computer Interface
keywords: COPD; Computed tomography; Emphysema; Subjective quantification