Radiation exposure with the RVG-S and conventional intraoral X-ray film

Oral Radiology (Impact Factor: 0.17). 05/1994; 10(1):33-40. DOI: 10.1007/BF02348012

ABSTRACT The exposure required to obtain optimal image quality was determined using conventional intraoral x-ray film (Eastman Kodak,
Rochester, NY) and the RVG-S Radio VisioGraphy-S: Trophy Radiology, Vincennes, France) CCD-based intraoral radiographic imaging
system. The RVG-S permitted dose reductions of 50 to 65% for individual exposures in comparison with Ektaspeed film, and 73
to 76% when compared to Ultraspeed film. The dose dynamic for the RVG-S was 8.6 times narrower than that for conventional
film. Perception of low contrast details was not significantly different between either type of x-ray film and the RVG-S.

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    ABSTRACT: PurposeCurrent 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). MethodsImages 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. ResultsThe 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. ConclusionsThe 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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    ABSTRACT: ObjectivesThis study investigated the effect of the size of the sensitive area of the charge-coupled devices (CCD) used in digital intraoral radiographic systems on the patient effective dose in full-mouth radiographic examinations. MethodsThe effective dose was assessed in full-mouth radiographic examinations using the bisecting angle technique, while assuming that CCD sensitivity is equivalent to that of E-speed film. The results were compared with the effective doses obtained using E-speed film. The tube potentials used were 70, 80, and 90 kV. The diameter of the circular field at the cone tip was 7 cm, and the length of the spacer cone was 20 cm. Twelve types of CCD devices with sensitive areas ranging from 307 to 1200 mm2 were assessed in seven digital intraoral radiographic systems. ResultsThe number of exposures and effective dose using the CCD devices were inversely proportional to the sensitive area of the CCD. Both the number of exposures and the effective dose were increased when using a CCD with a sensitive area smaller than the intraoral film size. Consequently, a reduction in the patient dose did not occur to the extent expected, based on the relative sensitivity of the CCD to film. ConclusionsIn order to fully realize the advantages of a CCD, it will be necessary both to reduce the frequency of examinations and to use a rectangular-shaped beam in CCD-based intraoral radiographic systems.
    Oral Radiology 22(2):62-68. · 0.17 Impact Factor
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    ABSTRACT: Cutoff frequency images eliminating radiographic information of high frequency areas were obtained using a low-pass filter in a spatial frequency domain and inverse fast Fourier transform processing. Using these images, the spatial frequency range of the radiographic information necessary for the X-ray diagnosis of normal anatomical structures on intraoral computed radiography was investigated. Normal anatomical structures were evaluated on either gradational enhancement images or frequency-enhanced images, from which the frequency range of 2.0–3.0 cycles/mm had been eliminated. The mean value of spatial frequency components did not differ markedly between the frequency-enhanced images and the gradational enhancement images. However, the evaluations made by different examiners varied less in the case of the frequency-enhanced images. The diagnostic ability demonstrated, with film output images and cathode ray tube (CRT) output images, was within a narrow range. This indicates that images displayed on monitors are as useful diagnostically as conventional dental film images. These results suggest that the maximum spatial frequency required for the evaluation of normal anatomical structures in intraoral radiography is 3.0 cycles/mm. Also, diagnosis is possible from the CRT, and it is unnecessary to output the image to film.
    Oral Radiology 11/1995; 11(2):37-46. · 0.17 Impact Factor