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首页> 外文会议>Ultrasonics Symposium (IUS), 2009 >Time-domain model of the ultrasonic wave propagation in an inhomogeneous anisotropic viscoelastic fluid/solid multilayer medium: application to cortical bone
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Time-domain model of the ultrasonic wave propagation in an inhomogeneous anisotropic viscoelastic fluid/solid multilayer medium: application to cortical bone

机译：非均质各向异性粘弹性流体/固体多层介质中超声波传播的时域模型：在皮质骨中的应用

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Cortical bone quality is assessed in clinical practice using axial transmission (AT) devices, which allow the measurement of quantitative ultrasonic parameters such as the first arriving signal (FAS) velocity. However, the physical interaction between an ultrasonic wave and cortical bone remains poorly understood due to the complex nature of the bone structure. Cortical bone and the surrounding soft tissues are attenuating media, which might affect the analysis of the results obtained with AT devices. Moreover, cortical bone is highly heterogeneous and a gradient of material properties from the outer to inner part of the cortical shell has been reported. The aim of this work is to evaluate the effect of anisotropic heterogeneous dissipative phenomena occurring in bone and in soft tissues on the ultrasonic response of the bone structure. A two-dimensional finite element time-domain method is derived to model transient wave propagation in a three-layer medium composed of an inhomogeneous transverse isotropic viscoelastic solid layer sandwiched between two dissipative acoustic fluid layers. The model couples acoustic propagation in both dissipative acoustic fluid media with the response of the solid whose constitutive equation is based on the linear theory of viscoelasticity without memory. Bone viscoelasticity is assumed to be heterogeneous and a constant spatial gradient of viscoelastic properties is considered for a value of bone thickness corresponding to a relatively thick bone. Realistic variations of the viscosity of the soft tissues within the physiological range do not affect the FAS velocity in any configuration. However, when the viscoelastic bone parameters vary within their physiological range, changes of the value of the FAS velocity (up to 301 m/s) are comparable to what has been obtained for variation of the elastic parameters. The components of the viscoelastic tensor affecting the results are the same as those of the stiffness tensor found. Our result-s highlight the importance of accounting for absorption phenomena occurring in cortical bone for the analysis of ultrasonic measurements with AT device.
机译：在临床实践中，使用轴向传输（AT）设备评估皮质骨质量，该设备可以测量定量超声参数，例如首次到达信号（FAS）速度。但是，由于骨骼结构的复杂性，超声波与皮质骨骼之间的物理相互作用仍然知之甚少。皮质骨和周围的软组织是衰减介质，这可能会影响对使用AT设备获得的结果的分析。此外，皮质骨是高度异质的，并且已经报道了从皮质壳的外部到内部的材料特性的梯度。这项工作的目的是评估在骨骼和软组织中发生的各向异性异质耗散现象对骨骼结构超声响应的影响。推导了二维时域有限元方法，以模拟瞬变波在三层介质中的传播，该介质由夹在两个耗散声流体层之间的不均匀横向各向同性粘弹性固体层组成。该模型将两种耗散声流体介质中的声传播与固体的响应耦合，该固体的本构方程是基于粘弹性线性理论而无记忆的。假定骨粘弹性是异质的，并且对于对应于相对较厚的骨头的骨厚度值，认为粘弹性特性的空间梯度恒定。生理范围内软组织粘度的实际变化在任何配置下均不影响FAS速度。但是，当粘弹性骨参数在其生理范围内变化时，FAS速度值（最高301 m / s）的变化与弹性参数变化所获得的变化相当。影响结果的粘弹性张量的分量与发现的刚度张量的分量相同。我们的结果- s强调了考虑使用AT设备进行超声测量时分析皮质骨中发生的吸收现象的重要性。

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