The wall motion of atherosclerotic plaque was analyzed using a computational method, and the effects of tissue viscoelasticity, fibrosis thickness, and lipid-core stiffness on wall displacement waveforms were examined. The viscoelasticity of plaque tissues was modeled using a time Prony series with four Maxwell elements. Computational simulation of tissue indentation tests showed the validity of the proposed viscoelastic constitutive models. Decreasing the relative moduli of the viscoelastic model reduced their viscous characteristics while enhancing the stiffness of the wall, which corresponded with the effects of decreased smooth muscle cells content. A finite-element analysis was conducted for atherosclerotic wall models and wall displacement waveforms were computed. The phase difference between the first harmonics of pressure and displacement waves was selected to represent the time delay of the wall motion. As the relative modulus decreased, the wall displacement and phase lag decreased. A thinner wall and softer lipid core corresponded to a greater wall displacement and smaller phase lag. Because the phase lag of the arterial-wall motion was smaller for the plaque with a thinner cap, lower smooth muscle cells content, and softer lipid core (all features of plaques with high rupture risk), first harmonics of pressure and displacement waves can be used as an index to assess plaque vulnerability.

中文翻译：

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用于评估斑块易损性的动脉壁运动相位滞后的计算研究。

使用计算方法分析了动脉粥样硬化斑块的壁运动，并研究了组织粘弹性，纤维化厚度和脂质核心硬度对壁位移波形的影响。使用具有四个麦克斯韦元素的时间Prony系列对斑块组织的粘弹性进行建模。组织压痕试验的计算仿真表明了所提出的粘弹性本构模型的有效性。减小粘弹性模型的相对模量可降低其粘滞特性，同时提高壁的刚度，这与减少平滑肌细胞含量的效果相对应。对动脉粥样硬化壁模型进行了有限元分析，并计算了壁位移波形。选择压力和位移波的一次谐波之间的相位差来表示壁运动的时间延迟。随着相对模量的减小，壁位移和相位滞后减小。较薄的壁和较软的脂质核心对应于较大的壁位移和较小的相位滞后。因为具有较薄帽盖的斑块，较低的平滑肌细胞含量和较软的脂质核心（斑块的所有特征均具有高破裂风险）的斑块的动脉壁运动的相位滞后较小，所以压力和位移波的一次谐波可以是用作评估菌斑脆弱性的指标。较薄的壁和较软的脂质核心对应于较大的壁位移和较小的相位滞后。因为具有较薄帽盖的斑块，较低的平滑肌细胞含量和较软的脂质核心（斑块的所有特征均具有高破裂风险）的斑块的动脉壁运动的相位滞后较小，所以压力和位移波的一次谐波可以是用作评估菌斑脆弱性的指标。较薄的壁和较软的脂质核心对应于较大的壁位移和较小的相位滞后。因为具有较薄帽盖的斑块，较低的平滑肌细胞含量和较软的脂质核心（斑块的所有特征均具有高破裂风险）的斑块的动脉壁运动的相位滞后较小，所以压力和位移波的初次谐波可以是用作评估菌斑脆弱性的指标。