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  • 11
    ISSN: 1613-9674
    Keywords: intraoral radiography ; computed radiography ; low-pass filter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: 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.
    Type of Medium: Electronic Resource
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  • 12
    ISSN: 1613-9674
    Keywords: Subtraction CT ; Maxillary sinusitis ; Maxillary cancer ; Highspeed serial scanning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract This study was conducted to investigate the usefulness of subtraction CT for diagnosing lesions of the maxillary sinus, and to compare the enhancement patterns of maxillary cancer and unilateral chronic maxillary sinusitis. Twenty-two cases of unilateral chronic maxillary sinusitis and four cases of maxillary cancer were reviewed. The subtraction images were classified according to the following three patterns: no enhancement, linear enhancement, and heterogeneous enhancement. In unilateral chronic maxillary sinusitis, no enhancement was found in 41% of the cases, linear enhancement in 50%, and heterogeneous enhancement in 9%. Conversely, while all cases of maxillary cancer showed a heterogeneous enhancement pattern of the soft tissue lesion, there were no cases which also showed areas of no enhancement or of linear enhancement. In conclusion, it was suggested that this enhancement pattern might be used supplementary to differentiate maxillary cancer from unilateral chronic maxillary sinusitis.
    Type of Medium: Electronic Resource
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  • 13
    Electronic Resource
    Electronic Resource
    Springer
    Oral radiology 11 (1995), S. 64-64 
    ISSN: 1613-9674
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 14
    Electronic Resource
    Electronic Resource
    Springer
    Oral radiology 11 (1995), S. 65-65 
    ISSN: 1613-9674
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 15
    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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  • 16
    Electronic Resource
    Electronic Resource
    Springer
    Oral radiology 12 (1996), S. 1-10 
    ISSN: 1613-9674
    Keywords: Magnetic resonance (MR) imaging ; Multi-functional phantom ; Surface coil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A multi-functional phantom was developed for Magnetic resonance (MR) imaging using a surface coil by combining a single signal-producing material and a non-signal-producing material to evaluate spatial resolution, slice thickness, image distortion, the signal-to-noise ratio (SNR), and image uniformity. The phantom was examined by comparing the preset and measured values of varying scan conditions, such as matrix size, field of view (FOV), and slice thickness. The results illustrated that the spatial resolution increased as the pixel size decreased. The percent error in slice thickness increased as the preset slice thickness value was reduced. The image distortion decreased as the FOV became smaller. The SNR increased as the slice became thicker. The image uniformity ranked high within the effective sensitivity range of the surface coil. These results were consistent with the theoretical MR imaging characteristics. Therefore, it was concluded that the developed phantom is effective as a multi-functional phantom for MR imaging using surface coils.
    Type of Medium: Electronic Resource
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  • 17
    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.
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  • 18
    ISSN: 1613-9674
    Keywords: 99mTc-MDP ; Hydroxyapatite ; Adsorption ; Bone scintigraphy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The accumulation mechanisms of technetium-99m methylene diphosphonate (99mTc-MDP) were investigated using hydroxyapatite powder and various phosphates. After reaction with99mTc-MDP, radioactivity was analyzed using a scintillation counter. The adsorption of99mTc-MDP onto hydroxyapatite occurred within 30 sec, and was not temperature dependent at 0–95°C. There was no change in the adsorption of99mTc-MDP onto hydroxyapatite in 5 or 50mM water-soluble organic compounds (glucose or urea). Anions had a greater effect on adsorption than cations. The only phosphate with adsorption equal to that of hydroxyapatite was calcium pyrophosphate. Adsorption onto calcium hydrogenphosphate was low at a pH of 6.0 in comparison with hydroxyapatite. These findings suggest that the adsorption of99mTc-MDP onto hydroxyapatite is influenced by the concentration of coexisting anions and by the chemical constitution of the phosphate components.
    Type of Medium: Electronic Resource
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  • 19
    ISSN: 1613-9674
    Keywords: Irradiation effect ; Growth plate chondrocytes ; Cytodifferentiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of X-ray irradiation on the proliferation and differentiation of growth plate chondrocytes were examined. Chondrocytes were isolated from the ribs of 4-week-old New Zealand white rabbits and cultured as a packed mass in centrifuge tubes. The cells in the centrifuge tubes proliferated, matured and hypertrophied likein vivo chondrocytes. Irradiation at a dose as low as 3 Gy to proliferating chondrocytes significantly decreased the DNA content, alkaline phosphatase (ALPase) activity, and matrix calcification, without decreasing the proteoglycan content. Irradiation at 10Gy to mature chondrocytes caused significant decrease in ALPase activity and matrix calcification, although it did not have marked effects on DNA and proteoglycan contents. On the other hand, irradiation at 10Gy to hypertrophic chondrocytes did not cause any change in ALPase activity or cartilage-matrix calcification. These findings suggest that the irradiation sensitivity of chondrocytes changes during cytodifferentiation. Furthermore, the inhibition of ALPase expression and matrix calcification by irradiation proved to be independent of the suppression of proliferation.
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  • 20
    ISSN: 1613-9674
    Keywords: Double mental foramina ; Double mandibular foramina ; Double mandibular canals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We report a forensic case in which bilateral double mental foramina with double mandibular foramina, and double mandibular canals on the left side of the lower jaw were noted in the bleached white skull of an unidentified Japanese male of the estimated age of 50 years.
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