The perceptibility curve test applied to CCD and two methods of digitization of dental film-based radiographs

After introduction of digital radiography into dentistry several methods of image acquisition were accessible in the field of dentistry. In many instances it is necessary to digitize analog images. There is no overall acceptable method for image digitization so all different types of
images can be comparable. The objective of this study was to compare the diagnostic accuracy of different methods of image digitization.
This study was an accuracy diagnostic test study. In current study perceptibility curve test which first introduced by de Balder was applied. In this test a test object is used which is usually made by aluminum. Different levels of thickness are necessary and there are a number of holes in the test object to have different levels of contrast. Images from film and CCD and digitized images by means of CCD scanners and digital camera were prepared. Nine observers assessed the images. Data collected from observers delivered to SPSS software (SPSS 13.0, Chicago, IL) and for each image acquisition method interclass correlation coefficience (ICC) was computed and compared to the gold standard.
Mean sensitivity, specifity, positive and negative like hood ratios in dependence on material thickness (steps) and the background gray value were calculated. In regions of high optical density (dark images, low gray value in background) the sensitivity for the film images was highest (0.994) following by CCD (0.905), scanner (0.889) and camera (0.821). Difference between CCD images and scanner images was not significant. (P >0.05) In dark regions of no dark holes the sensitivity was highest for film images (0.832) following by CCD (0.798), camera (0.714) and scanner (0.615) Difference between film and CCD images was not significant. (P >0.05).
The diagnostic quality of radiographic films was better than digital CCD sensors. And for digitizing analog images scanners are better than digital cameras.