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This study investigated the possibility of using a video display system instead of film for radiological diagnosis. Also investigated were the relationships between characteristics of the system and the observer's accuracy level. Radiologists were used as observers. Thirty-six clinical bone fractures were separated into two matched sets of equal difficulty. The difficulty parameters and ratings were defined by a panel of expert bone radiologists at the Arizona Health Sciences Center, Radiology Department. These two sets of fracture images were then matched with verifiably normal images using parameters such as film type, angle of view, size, portion of anatomy, the film's density range, and the patient's age and sex. The two sets of images were then displayed, using a counterbalanced design, to each of the participating radiologists for diagnosis. Whenever a response was given to a video image, the radiologist used enhancement controls to "window in" on the grey levels of interest. During the TV phase, the radiologist was required to record the settings of the calibrated controls of the image enhancer during interpretation. At no time did any single radiologist see the same film in both modes. The study was designed so that a standard analysis of variance would show the effects of viewing mode (film vs TV), the effects due to stimulus set, and any interactions with observers. A signal detection analysis of observer performance was also performed. Results indicate that the TV display system is almost as good as the view box display; an average of only two more errors were made on the TV display. The difference between the systems has been traced to four observers who had poor accuracy on a small number of films viewed on the TV display. This information is now being correlated with the video system's signal-to-noise ratio (SNR), signal transfer function (STF), and resolution measurements, to obtain information on the basic display and enhancement requirements for a video-based radiologic system. Due to time constraints the results are not included here. The complete results of this study will be reported at the conference.
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