Diagnostic image quality of video-digitized chest images : a phantom study

The diagnostic accuracy obtained within the Philips picture archiving and communications subsystem was investigated by means of an observer performance study using receiver operating characteristic (ROC) analysis. The image qualities of conventional films and video digitized images were compared. The scanner had a 1024 x 1024 x 8 bit memory. The digitized images were displayed on a 60 Hz interlaced display monitor with 1024 lines. Poster anterior (AP) roentgenograms of a chest phantom with superimposed simulated interstitial pattern disease (IPD) were produced; there were 28 normal and 40 abnormal films. Normal films were produced by the chest phantom alone. Abnormal films were taken of the chest phantom with varying degrees of superimposed simulated disease, ranging from weak to strong. We advocate the use of simulated diffuse IPD instead of pulmonary nodule disease (PND) for an observer performance study, because the results of a simulated interstitial pattern disease study are less likely to be influenced by perceptual capabilities. The conventional films and the video digitized images were viewed by five experienced observers during four separate sessions. Conventional films were presented on a viewing box, the digital images were displayed on the monitor described above. The presence of simulated interstitial disease was indicated on a 5-point ROC certainty scale by each observer. We analyzed the differences between ROC curves derived from correlated data statistically. The mean time required to evaluate 68 digitized images is approximately four times the mean time needed to read the conventional films. The diagnostic quality of the video digitized images was significantly lower (at the 5% level) than that of the conventional films (median area under the curve (AUC) of 0.71 and 0.94, respectively).