Effects of calibration and automatic greyscale adjustment on detectability of simulated bone lesions using a storage phosphor system.

OBJECTIVES: To analyse the interaction of calibration, automatic greyscale adjustment and X-ray exposure on the evaluation of simulated bone lesions with the Digora (Orion Corporation Soredex, Helsinki, Finland) storage phosphor system. METHODS: Exposures were made under five conditions based on the exposure time for Ektaspeed Plus film: A-calibration exposure 100%, exposure 100%; B-calibration exposure 100%, exposure 50%; C-calibration exposure 100%, exposure 10%; D-calibration exposure 50%, exposure 50%; E-calibration exposure 10%, exposure 10%. Series of images of artificial bone lesions were created each representing one of the five conditions, with or without automatic greyscale adjustment and including one of two lesion sizes. The series were evaluated by seven expert radiologists. Results were analysed by means of MANOVA statistics. RESULTS: The large lesions were evaluated significantly better than the small lesions (P < 0.011). The two 10% exposure conditions were evaluated significantly worse than the other three (P < 0.029) which had comparable results. Automatic greyscale adjustment had no significant effect (P > 0.253). CONCLUSIONS: The Digora should be calibrated for the highest exposure to be used to optimize the wide latitude. Automatic greyscale adjustment is not useful for the detection of simulated bone lesions.

Reduction in size of digital images: does it lead to less detectability or loss of diagnostic information? .

OBJECTIVES: To analyse the effect of reduction in size of digital images on diagnostic outcome. METHODS: A series of 100 Visualix III (Gendex Dental Systems, Milano, Italy; Dentsply, Des Plaines, IL, USA) images was made of size 10 and 15 endodontic files in upper and lower (pre)molars. Three forms of image were created: (a) the original images, (b) reduced to one-half (containing one-quarter of the information of the original, and (c) zoomed-in, half-size images (magnification 2:1; original image size but with only one-quarter of the original information). Seven radiologists were asked to rate the position of the tip of the file, using a five-point confidence scale. ROC data were analysed by means of MANOVA statistics. RESULTS: A significant difference was found between the three image modalities for both size 10 (P < 0.005), and size 15 (P < 0.021) files. CONCLUSIONS: Reduction in size of digital images may cause less detectability as well as loss of diagnostic information.

An evaluation of periapical radiography with a charge-coupled device.

OBJECTIVES: To compare the standards of periapical radiography with a CCD-image receptor with film. METHODS: Three radiography technicians exposed a total of fifty teeth from all areas of the jaws using either size 1 or size 2 film and the Sidexis (Siemens, Bensheim, Germany) direct digital dental radiography system with the appropriate film holders. Image quality was assessed by two dental radiologists for nine individual criteria and overall, on a three-point scale. RESULTS: There was a significant difference between film and sensor exposures (P < 0.014). Six per cent of dental films required retakes compared with 28% with the sensor. CONCLUSION: Periapical radiography with a CCD sensor leads to more errors and thus more retakes than conventional film.

Efficacy of digital intra-oral radiography in clinical dentistry.

OBJECTIVES: This article emphasizes the comparison of intra-oral digital imaging to film-based imaging. Additional possibilities of digital imaging that may contribute to system efficacy are discussed as well. STUDY SELECTION: The main subjects for research in digital imaging are image quality, image acquisition, diagnostic quality, image manipulation, automated analysis, and application software. DATA SOURCES: Representative articles on these subjects from the international literature are used for this review. Indirect digital imaging still requires film processing, sophisticated film digitizers, and time to digitize film. Although it is not an efficient method for the dental practice, digitization can be very useful for quantitative analysis of radiographs. Direct digital imaging is more efficient than indirect digital imaging. The main advantages are (semi) real time imaging, low X-ray dose requirements, and no need for chemical processing. In spite of a more limited resolution of the images, direct imaging may perform as accurately as film-based imaging. Direct image plate systems can well be used, for instance, for full-mouth series. The main application of direct sensor systems appears to be endodontology and implantology. In summary, direct digital imaging may be as efficient as film-based imaging in clinical dentistry. The computer provides for many additional options in digital imaging, such as the digital storage, compression, and exchange of radiographic information. Image manipulation (e.g. image enhancement, subtraction radiography and image reconstruction) and automated analysis may benefit radiodiagnosis. CONCLUSION: It can be concluded that digital imaging certainly has great potential, especially with respect to improvement of diagnostic quality and automated image analysis.

Impact of scale standardization on images of digital radiography systems.

OBJECTIVES: To test the effect of altering image size on diagnostic quality. METHODS: Endodontic files, size 10 and 15 were prepared to full root length and 1.5 mm short, in upper and lower molars and premolars. Digital images of the Sidexis (S) and Visualix/Vixa (V) system were reduced in size to Digora (D) scale, and the D images were enlarged to S scale. ROC analysis was performed and data analysed with MANOVA statistics. RESULTS: Assessment of root canal length with file size 10 was less accurate for the S images reduced in size, compared with the original S images (P < 0.011). All other differences were not significant (P > 0.081). CONCLUSIONS: Relevant diagnostic information may be lost when images are reduced in size. Therefore, for optimal presentation, the smaller images should be enlarged rather than the larger ones reduced.