Measuring System for Bone Mineral Content by Panoramic Radiography

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The investigation of bone mineral content(BMC) is useful for osteoporosis screening and for accurate prognosis for implant treatment. BMC was measured by special devices, as quantitative computed tomography. In this study, BMC measuring system was improved by using panoramic X-ray system to obtain overall coverage of the dental arches and associated structures at a time. We surveyed the measuring performance of this system.We applied bone phantom to reference and test stepwedges, X500CR(Morita Co.Ltd.) to panoramic X-ray system and Denoptix digital imaging system ( Dentsply Co. Ltd.) to image input device. The exposure condition was 60kV, 10mAs. The reference stepwedge was fixed at left side on image layer, the position of test stepwedge was changed as followings 1)inside or outside of the layer, 2) in premolar or molar region. We verified the measuring accuracy and reproducibility of this system at each condition.Measured value in molar region was higher than that in premolar region. The variation of measured value depended on the measuring position. The accuracy of adjusted RMET value was 1.25%(relative error). The difference in the magnification between in the mesial and the distal region was detected. The conversion corresponding with the position in mandible decreased the distortion. The BMC value from this study showed 1.7 times as large as from previous method, however, the distribution of BMC from this study was similar to one from previous method.The results demonstrated that the measuring system was able to measure BMC in edentulous mandible and that this system may be useful for an accurate prognosis for implant treatment and for osteoporosis screening.