[Relationship between image quality and signal detectability in CR and FPD systems]

With the screen/film X-rays imaging system, Wakamatsu et al. reported that there was a close relationship between the square root of spectral signal-to-noise ratio area and sensitivity measure d' in receiver operating characteristic (ROC) analysis. In this study, we investigated the relationship between image quality and signal detectability in two digital X-ray imaging systems using computed radiography (CR) and a flat panel detector (FPD). We used urethane resin balls with a diameter of 2 mm as a signal for cases samples in ROC analysis. In this experiment, the square root of the spectral signal-to-noise ratio area was closely related to d' in ROC analysis in both digital X-ray imaging systems. In addition, when the exposure dose increased, signal detectability improved, but then saturated at one level. These results suggest that the exposure dose can be reduced when the optimal dose setting can be determined.