Exposure parameters in sens-a-ray direct digital radiography and their effects on diagnostic accuracy of carious lesions

We studied the effects of tube potentials and exposures on the accuracy of carious diagnosis using Sens-A-Ray direct digital radiography with two types of CCD detectors, one without and one with a scintillator layer. Our second objective was to determine the optimum exposure factors. Radiographs of 75 extracted premolars with and without clinically observed discolorations or cavities were obtained at exposure settings of 70 kVp and 90 kVp. The observers diagnosed dental caries in radiographs exposed with the two types of detectors. The results were analyzed with Receiver Operating Curve (ROC) technique. The averaged areas under the ROC curves were plotted as functions of exposure to obtain Diagnostic Accuracy (DA) curves. No statistically significant difference was found in diagnostic accuracy for the two tube potentials. However, there was a statistically significant difference in diagnostic accuracy for the two lesion types, discolorations and cavities. There was also a significant effect on diagnostic accuracy related to exposure: the exposure providing the optimum diagnostic accuracy corresponds to a gray level of about 31 when SVGA graphics are employed, i.e., in the middle of the available range. To acquire optimum radiographs for diagnosing carious lesions with the Sens-A-Ray system, the operator must select the appropriate exposure parameters.