Comparison of trained and untrained observers using subjective and objective measures of imaging performance

Rationale and Objectives. 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. Conclusion. 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.