Quantitative Study in Absorption of Mandible Caused by Aging and Disease

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Absorption of mandible is caused by aging, desease, and prosthetic Factors. It is difficult to estimate these absorption, and if possible, that is useful information for the prosthetic treatment, design and prognosis of prosthetics. Therefore, there were many studies in absorption of mandible with the tool of radiology, histology and biochemistry. But, there was no quantitative study in absorption of mandible and no method which can make quantitative measurements of bone mineral content. In this respect, we developed a sistem which can produce a quantitative image of bone mineral content. The system consists of a radiographing system and an image processor. Two radiograms were taken with dual X-ray energy in a single exposure using an X-ray beam dichromized by a tin filter. The image processing included the corrections of the film characteristics and heterogeneity in the X-ray field, and the dual energy subtraction in which the effect of the high energy component of the dichromized beam on the tube side image as corrected. In order to determine conditions of exposure of X-ray and some parameters of image analysis, experiments using wedge phantoms made of mixtures of epoxy resin and bone mineral-equvalent materials in various fractions were performed. The results as follows : the best tube potetials were from 60kV to 70kV.10x10 pixels image sample was suitable for image processing and it could make the best accuracy for the measurement of bone mineral content.