To understand the in-plane elastic character of ultrasonic waves in the skull, longitudinal wave velocities were studied in the MHz range using a conventional pulse technique. Taking advantage of the thickness of swine skulls, anisotropic in-plane wave velocity changes in the outer and diploe layers were experimentally investigated using structural information measured by X-ray computer tomography (CT). The velocities in the thin inner layer were difficult to measure. The main trabecular alignment (MTA) in the thick swine diploe layer was almost perpendicular to the thickness direction and changed with position inside the skull. The degree of anisotropy of in-plane longitudinal wave velocity ranged 1.07–1.33 in both outer and diploe layers, depending on position and swine sample. The angle of the fastest velocity in the outer layer was different from that in most parts of the diploe layer. Anisotropic character in the diploe layer gradually changed with position in the thickness direction.

中文翻译：

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猪头骨中各向异性纵向波的传播

为了了解头骨中超声波的面内弹性特征，使用常规脉冲技术研究了MHz范围内的纵向波速。利用猪头骨的厚度，利用X射线计算机断层扫描（CT）测量的结构信息，通过实验研究了外层和二倍体的各向异性面内波速变化。薄内层的速度很难测量。猪二倍体厚层中的主要小梁排列（MTA）几乎垂直于厚度方向，并随颅骨内位置的变化而变化。外层和二倍体层的面内纵波速度的各向异性程度在1.07-1.33之间，这取决于位置和猪样品。在外层中最快速度的角度与多数倍普洛层的角度不同。在厚度方向上，二倍体层中的各向异性特征逐渐变化。