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  • 1
    ISSN: 1613-9674
    Keywords: Dental Radiography ; CCD-based intraoral imaging system ; Signal-to-noise ratio
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The signal-to-noise ratio (SNR) describes the ability of a detector to differentiate a signal from random fluctuations in signal intensity or noise in an image. The dose-response curves and the SNRs were measured and compared between Computed Dental Radiography (CDR) and Sens-A-Ray. The dose-response curves at 60, 70 and 80 kVp of both systems indicated that the pixel values increased in proportion to the radiation exposure. The pixel value gradient was slightly steeper for the CDR than for the Sens-A-Ray. Sensitivity increased slightly at the higher kVp setting with the CDR only. All SNRs increased with increased exposure for both systems. The SNR for the CDR was superior to that for the Sens-A-Ray, even with low exposures. The SNR for CDR increased steeply as exposure and average pixel values increased. On the other hand, the SNR for the Sens-A-Ray showed only a relatively slight increase with exposure. In conclusion, due to the high SNR in the lower exposure range, the CDR has the capability of substantially reducing the level of exposure in comparison with the Sens-A-Ray.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1613-9674
    Keywords: Dental Radiography ; Digital image processing ; CCD-based intraoral radiographic system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The RVG-4 permits automatic exposure compensation (AEC). The purpose of this investigation was to determine the effects of AEC on image contrast. Images were made either with or without a dental QA jaw phantom using a fixed image projection geometry. Exposures were 6.3 through 27.3 μC/kg using an X-ray generator operated at 70 kVp. Region of interest pixel value distributions were measured at tissue thicknesses in this phantom, and the average pixel values and signal-to-noise ratios (SNR) were calculated. The use of AEC without an object in place resulted in a disproportionate relationship between pixel value and exposure with a marked reduction in SNR. The use of AEC on under- and over-exposed images of the phantom simultaneously enhanced image contrast and reduced SNR. Thus, AEC provides a convenient and quick method for achieving high-contrast images with sub-optimal exposures, however, this could lead to inappropriate patient dosages if the function is used for over-exposed images. AEC reduces the SNR and produces disproportionate pixel values relative to exposure.
    Type of Medium: Electronic Resource
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