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At least 109 records · Page 6Linked to original sources
PubMed1992

Effects of niobium filtration and constant potential on image quality in dental radiography. 2. Objective assessment.

The effects of niobium filtration and constant potential on image quality were explored by asking observers to identify numbers of circular areas of small density differences in zones of high and low density. Successful identification was related negatively to half-value layer. This relationship was particularly strong in the case of self-rectified units without additional niobium filtration and the constant potential units (r2 = 0.994, P < 0.0005). Constant potential had no effect other than in relation to half-value layer. Additional niobium filtration detracted from successful identification, but slightly less than would be predicted by the half-value layer. Whether this difference is significant or relevant has not been established. The findings of this study, in conjunction with our previous investigations, have failed to demonstrate any clear indications for preferring constant potential supply over self-rectification or for using niobium as an additional filter material. Half-value layer has been shown to be a reliable indicator of the effects of beam quality on emulsion speed, attenuation in water, and image quality. It appears that the methods employed to change the beam quality have no specific effects.

Filtration↗
PubMed1996

Correction of background noise in direct digital dental radiography.

OBJECTIVES: To clarify the source of noise in direct digital intra-oral radiography with RVG-S (Trophy Radiologie, Vincennes, France) and to use these to develop a method for correction of background noise. METHODS: Sensor temperature, image acquisition time and X-ray dose were independently analysed with the IPLab Spectrum (Signal Analytics, Vienna, VA) software. RESULTS: The decrease in pixel value due to the dark current was linearly related to the image acquisition time. Although a variation in sensitivity was observed when the sensor was exposed to X-rays, the mean pixel value of the entire image was linearly related to the exposure time. The image showing only the signal due to X-ray dose was derived from the original RVG-S image by correcting for the dark current and the pixel-by-pixel sensitivity variation of the CCD sensor. CONCLUSION: The image formed only by X-ray dose distribution can be derived by correcting for the background noise.

Algorithms↗