Measuring System for Bone Mineral Content by Panoramic Radiography

骨矿含量(BMC)的调查有助于骨质疏松的筛查和种植体治疗的准确预后。用定量CT等特殊设备测量BMC。本研究利用全景X线机对BMC测量系统进行了改进，一次可获得牙弓及相关结构的全程覆盖。对该系统的测量性能进行了考察，并应用骨模对X500CR(森田株式会社)步进楔进行了参照和测试。至全景X射线系统和Denoptix数字成像系统(Dentsply Co.Ltd.)到图像输入设备。照射条件为60KV，10mAs。将参考台阶固定在图像层左侧，改变测试台阶的位置：1)层内或层外，2)在前磨牙或磨牙区。验证了该系统在各种条件下的测量精度和重复性，磨牙区的测量值高于前磨牙区的测量值。测量值的变化与测量位置有关。调整后的RMET值的准确度为1.25%(相对误差)。观察到近端和远端的放大倍数的差异。与下颌骨位置对应的转换减少了变形量。结果表明，该测量系统能够准确测量无牙下颌骨的骨矿含量，为种植体治疗和骨质疏松筛查提供了准确的预测依据。

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.