IEEE Trans Ultrason Ferroelectr Freq Control. 2021 Jun;68(6):2129-2140. doi: 10.1109/TUFFC.2021.3057309. Epub 2021 May 31.
We numerically and experimentally investigate the dispersion properties of leaky Lamb waves in the cranial bone. Cranial Lamb waves leak energy from the skull into the brain when propagating at speeds higher than the speed of sound in the surrounding fluid. The understanding of their radiation mechanism is significantly complicated by the geometric and mechanical characteristics of the cortical tables and the trabecular bone (diploë). Toward such understanding, we here analyze the sub-1.0 MHz radiation angle dispersion spectrum of porous bone phantoms and parietal bone geometries obtained from μ CT scans. Our numerical results show that, when diploic pores are physically modeled, leakage angles computed from time transient finite-element analyses correspond to those predicted by an equivalent three-layered fluid-loaded waveguide model. For the bone geometries analyzed, two main leaky branches are observed in the near-field dispersion spectrum: a fast wave radiated at small angles, which is related to the fastest fundamental Lamb mode supported by the cranial bone, and a slower wave radiated at larger angles. This observation is also confirmed by experimental tests carried out on an immersed parietal bone.
我们通过数值和实验研究了颅骨中漏声 Lamb 波的频散特性。当颅 Lamb 波以高于周围液体中声速的速度传播时，会从颅骨中漏出能量进入大脑。由于皮质板和小梁骨（板障）的几何形状和力学特性，它们的辐射机制的理解变得非常复杂。为了理解这一点，我们在这里分析了从 μ CT 扫描获得的多孔骨模型和顶骨几何形状的亚 1.0MHz 辐射角频散谱。我们的数值结果表明，当物理模拟板障孔隙时，从瞬态有限元分析计算得出的泄漏角与等效的三层充液波导模型预测的泄漏角相对应。对于分析的骨几何形状，在近场频散谱中观察到两个主要的漏波分支：在小角度辐射的快波，它与颅骨中支持的最快的基本 Lamb 模式有关，以及在较大角度辐射的慢波。这一观察结果也通过在浸入式顶骨上进行的实验测试得到了证实。
