OBSERVERS USE OF IMAGE-ENHANCEMENT IN ASSESSING CARIES IN RADIOGRAPHSTAKEN BY 4 INTRAORAL DIGITAL-SYSTEMS

Objectives. To evaluate observers' use of image-enhancement facilities and time consumption in assessing caries in radiographs taken with fo ur digital systems. Methods. In total, 131 extracted human premolars a nd molars were mounted three in a line. Radiographs were taken using f our digital systems: Digora (DIG), Radio VisioGraphy (RVG), Sens-A-Ray (SAR) and Visualix (VIX), and imported into a programme with routines for adjustment of brightness, contrast and gamma curve. Sixteen image s from each digital system were compressed (JPEG, irreversible compres sion). The 588 images were scored by six observers for approximal and occlusal caries on a five-point confidence scale using enhancement as they pleased. The programme automatically recorded any enhancement mad e without the observers knowing this. Results. Some form of digital en hancement was used in almost all images, with the gamma curve being th e most frequent. The VIX images were enhanced most followed by SAR, DI G and RVG images. The differences were significant (p < 0.01) except b etween DIG and SAR images. The compressed images were enhanced signifi cantly more than their uncompressed counterparts (p = 0.02). The avera ge time spent recording one image was 24 s. On average, significantly less time was spent with the DIG images than the other systems (p < 0. 01), while there were no significant differences between the CCD-based systems (p > 0.2). There was no relationship between time spent and n umber of manipulations performed. Conclusions. The observers took adva ntage of the facilities available for enhancement of density and contr ast in digital images. The potential of gamma curve manipulation requi res further investigation.