Nagatani Yoshiki, Mizuno Katsunori, Saeki Takashi, Matsukawa Mami, Sakaguchi Takefumi, Hosoi Hiroshi
Department of Otorhinolaryngology, Nara Medical University, 840 Shijo-cho, Kashihara, Nara 634-8522, Japan.
Ultrasonics. 2008 Nov;48(6-7):607-12. doi: 10.1016/j.ultras.2008.04.011. Epub 2008 May 13.
In cancellous bone, longitudinal waves often separate into fast and slow waves depending on the alignment of bone trabeculae in the propagation path. This interesting phenomenon becomes an effective tool for the diagnosis of osteoporosis because wave propagation behavior depends on the bone structure. Since the fast wave mainly propagates in trabeculae, this wave is considered to reflect the structure of trabeculae. For a new diagnosis method using the information of this fast wave, therefore, it is necessary to understand the generation mechanism and propagation behavior precisely. In this study, the generation process of fast wave was examined by numerical simulations using elastic finite-difference time-domain (FDTD) method and experimental measurements. As simulation models, three-dimensional X-ray computer tomography (CT) data of actual bone samples were used. Simulation and experimental results showed that the attenuation of fast wave was always higher in the early state of propagation, and they gradually decreased as the wave propagated in bone. This phenomenon is supposed to come from the complicated propagating paths of fast waves in cancellous bone.
在松质骨中，纵波常常会根据传播路径中骨小梁的排列情况分离成快波和慢波。这一有趣的现象成为骨质疏松症诊断的有效工具，因为波的传播行为取决于骨骼结构。由于快波主要在骨小梁中传播，所以该波被认为反映了骨小梁的结构。因此，对于一种利用这种快波信息的新诊断方法，有必要精确了解其产生机制和传播行为。在本研究中，通过使用弹性时域有限差分（FDTD）方法的数值模拟和实验测量来研究快波的产生过程。作为模拟模型，使用了实际骨样本的三维X射线计算机断层扫描（CT）数据。模拟和实验结果表明，快波在传播初期的衰减总是更高，并且随着波在骨中传播，衰减逐渐降低。这种现象应该源于快波在松质骨中复杂的传播路径。
