Ultrasound is now a clinically accepted modality in the management of osteoporosis. The most common commercial clinical devices assess fracture risk from measurements of attenuation and sound speed in cancellous bone. This review discusses fundamental mechanisms underlying the interaction between ultrasound and cancellous bone. Because of its two-phase structure (mineralized trabecular network embedded in soft tissue-marrow), its anisotropy, and its inhomogeneity, cancellous bone is more difficult to characterize than most soft tissues. Experimental data for the dependencies of attenuation, sound speed, dispersion, and scattering on ultrasound frequency, bone mineral density, composition, microstructure, and mechanical properties are presented. The relative roles of absorption, scattering, and phase cancellation in determining attenuation measurements in vitro and in vivo are delineated. Common speed of sound metrics, which entail measurements of transit times of pulse leading edges (to avoid multipath interference), are greatly influenced by attenuation, dispersion, and system properties, including center frequency and bandwidth. However, a theoretical model has been shown to be effective for correction for these confounding factors in vitro and in vivo. Theoretical and phantom models are presented to elucidate why cancellous bone exhibits negative dispersion, unlike soft tissue, which exhibits positive dispersion. Signal processing methods are presented for separating "fast" and "slow" waves (predicted by poroelasticity theory and supported in cancellous bone) even when the two waves overlap in time and frequency domains. Models to explain dependencies of scattering on frequency and mean trabecular thickness are presented and compared with measurements. Anisotropy, the effect of the fluid filler medium (marrow in vivo or water in vitro), phantoms, computational modeling of ultrasound propagation, acoustic microscopy, and nonlinear properties in cancellous bone are also discussed.

中文翻译：

---

超声与松质骨相互作用的机制：综述。

现在，超声已成为骨质疏松症管理中的一种临床公认方法。最常见的商用临床设备通过测量松质骨的衰减和声速来评估骨折风险。这篇综述讨论了超声和松质骨之间相互作用的基本机制。由于其两相结构（埋在软组织骨髓中的矿化小梁网络），其各向异性和不均匀性，使得松质骨比大多数软组织更难以表征。给出了衰减，声速，色散和散射对超声频率，骨矿物质密度，组成，微结构和力学性能的依赖性的实验数据。吸收，散射，描述了在体外和体内确定衰减测量时的相抵消和相抵消。声音度量的通用速度需要测量脉冲前沿的传播时间（以避免多径干扰），其衰减，色散和系统属性（包括中心频率和带宽）会大大影响其速度。然而，已经显示出理论模型对于在体外和体内纠正这些混杂因素是有效的。提出了理论模型和幻象模型以阐明为什么松质骨表现出负色散，而软组织却表现出正色散。提出了用于分离“快速”和“慢速”的信号处理方法 即使两个波在时域和频域重叠，也可以通过多孔弹性理论预测并支撑在松质骨中。提出了解释散射对频率和平均小梁厚度的依赖性的模型，并将其与测量结果进行了比较。还讨论了各向异性，流体填充介质（体内骨髓或体外水）的作用，体模，超声传播的计算模型，声学显微镜以及松质骨中的非线性特性。