THE PERCEPTIBILITY CURVE TEST APPLIED TO DIRECT DIGITAL DENTAL RADIOGRAPHY

Objective: To compare the effect of an additional scintillator layer o n the psychophysical properties of a CCD detector for digital dental r adiography. Methods: Radiographs of a test object containing ten holes of increasing depth were obtained throughout the exposure range of tw o CCD detectors at 70 and 90 kVp. One was the original detector for th e Sens-A-Ray system (Regam Medical Systems, Sundsvall, Sweden) and the other the same detector covered by a scintillator layer. Ten viewers evaluated the radiographs for the number of perceptible holes. From th ese data and the dose response functions for the two detectors, the mi nimum perceptible exposure difference was found. The reciprocal values of this parameter were plotted against the logarithm of exposure to c reate Perceptibility Curves (PCs). Results: The four PCs had essential ly the same shape and height. There was a shift to lower exposures in the PCs for the detector covered by a scintillator.Conclusions: The tw o detectors have essentially the same psychophysical properties. Since the detector covered by a scintillator layer is more sensitive, it sh ould be preferred for clinical practice since the dose to the patient is reduced.