Direct digital radiography for the detection of defects in a standard aluminium test object through composite resin...

While the RVG 32000 (Trophy Radiologie, Vincennes, France) is in wide use for direct digital intraoral radiography in dentistry, there is a dearth of information in the literature concerning the system's sensitivity to small changes in radiographic density consistent with initial and recurrent dental caries. A standardized 7 mm aluminium test block was used as a phantom for perceptibility testing of density changes, both with and without the superimposition of composite resin sheets of various thicknesses. Defects in the block were randomly positioned and varied from 0.1 to 1.5 mm. Thermal prints were used for evaluation. Standard linear images, with no enhancement, were compared with three enhanced modes, standard mode with gradient enhancement (enhanced standard), standard X-function and zoom high resolution (ZHR). Sensitivity improved in the following sequence: standard 0.58 < enhanced standard 0.75 < X-function 0.94 < ZHR 0.95. Accuracy improved in the following sequence: standard 0.45 < enhanced standard 0.58 < X-function 0.73 < ZHR 0.74. Specificity was 1.0 both for X-function and for ZHR. These two modes both proved significantly better (P < 0.05) for the detection of 0.1 mm defects than the other two modes tested. No significant difference was found between X-function and ZHR. As ZHR requires four times the radiation exposure as standard exposures with the X-function, the latter is preferred for the task described in this study.