Observer Performance Studies

Performance on Film vs. Monitor - Chest Radiography

The goal of this study [1] was to assess the suitability of using an image console monitor for interpretation of adult portable chest radiographs using ROC analysis and subjective evaluation techniques.



  • 80 Computed Radiography Chest Images
  • 25 subtle subsegmental atelectasis (AT)
  • 15 subtle pneumothorax (PT)
  • 40 no active disease (NAD)
  • Half of the images in each group contained a variety of tubes & lines.


CR film on a viewbox 1,024 x 1,538 resolution display monitor


6 radiologists Read each image twice (once on film, once on the monitor) Report diagnostic decision as AT, PT or NAD & give confidence using a 6-level scale Determine if tube/line placement was OK or not OK Subjectively rated the quality of film vs monitor


ROC Performance Analysis

  Az Film Az Monitor
PT 0.706 0.789
df = 5 t = -3.102 p = 0.03
AT 0.903 0.934
df = 5 t = -1.21 p = 0.28

Tube/Line Placement

86% agreement in confidence of placement between film & monitor 10% complete disagreement 4% cannot tell ratings

Viewing Time

Film : average = 33.63 sec per image Monitor : average = 99.82 sec per image df = 5, t = 10.89, p = .0001 Time to manipulate images on monitor = 13.7 sec on average out of the 99.82 sec vs 5.2 sec to hang a new film out of the 33.63 sec

Use of Image Processing

100% of readers used window/level 67% of readers used enlarge function 17% of readers used bold/edge enhance function

Subjective Quality Ratings of Monitor

Overall image quality : good/excellent Structure visibility : good Monitor rated same as or somewhat better than film


  • Viewing computed radiography chest images on a monitor does not affect diagnostic accuracy
  • Tube/line placement judgements are equivalent for film & monitor
  • Viewing time is significantly longer on the monitor than film
  • Very few image processing functions are used during monitor viewing

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