title: Comparison of trained and untrained observers using subjective and objective measures of imaging performance.
abstract: OBJECTIVE
  We compared subjective and objective measures of imaging performance using variations of Rose- and Burger-type low-contrast phantoms with trained (radiology residents) and untrained (graduate students) observers.
  
  
  METHODS
  With one phantom variant, observers indicated the total number of objects seen when test objects were presented in a regular pattern (subjective). With the second phantom variant, observers stated whether a low-contrast disk was present in each locale, thereby permitting the true-positive fraction and false-positive fraction to be determined (objective).
  
  
  RESULTS
  The untrained-observer group had a significantly lower imaging performance than the trained observer group in subjective tests. These differences were not found on objective tests. For the trained-observer group, similar contrast levels were required in subjective and objective tests to yield a 50% rate of detection.
  
  
  CONCLUSIONS
  Trained observers are superior subjects compared with untrained observers for assessing imaging performance using subjective low-contrast phantoms. In experiments using phantoms that allowed objective testing, both groups of observers yield similar results.
authors.affiliation: Department of Radiology, College of Medicine, University of Florida, Gainesville 32610-0374, USA.
authors.forename: G
authors.initials: G
authors.lastname: Qu
authors.forename: W
authors.initials: W
authors.lastname: Huda
authors.forename: C J
authors.initials: CJ
authors.lastname: Belden
mesh_terms: D004522:Educational Status; D006801:Humans; D007396:Internship and Residency; D015588:Observer Variation; D019047:Phantoms, Imaging; D011859:Radiography; D011871:Radiology / Q000193:education; D013334:Students