Digital image processing
CCD-based intraoral radiographic system
Springer Online Journal Archives 1860-2000
Abstract Purpose Current CCD-based intraoral radiographic systems permit the use of any dental X-ray generator. As a consequence, beam quality can be altered. This study was carried out to investigate studied the effects of varying beam quality on the VIXA-2 image contrast (Gendex Dental Systems srl Milan, Italy). Methods Images were made of a standard aluminum stepwedge and the pixel value of each step was measured. An optical bench was used to standardize geometric projection. Soft-tissue equivalent attenuation was effected using 1.75 cm plexiglass. Exposures were made at 2–48 impulses using 50–90 kVp settings at 10 kVp intervals. Exposures (μC/kg) were determined using a beryllium-windowed ionization chamber. Results The pixel values for each step decreased both with increased exposure (μC/kg) and with increased kVp. The relationship between exposure and pixel value was not linear. The longest scale of contrast was obtained at 17.3, 15.2, 13.5, 11.7, and 11.3 μC/kg respectively at 50, 60, 70, 80, and 90 kVp. The gradient for pixel values along the steps was steeper at lower kVp settings than at higher kVp settings. Conclusions The VIXA-2 can be operated at a wide range of kVp settings. Gamma conversion inherent in the VIXA-2 creates wide variations in the pixel values for different stepwedge thicknesses.
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