Laboratorio de Imágenes Médicas, Pontificia Universidad Católica del Perú, Lima, Peru.
Centre for Biomechanics and Rehabilitation Technologies, Staffordshire University, Stoke-on-Trent, United Kingdom.
Phys Med Biol. 2023 May 5;68(10). doi: 10.1088/1361-6560/acc923.
. The mechanical behaviour of soft tissue is influenced by its elastic and viscous characteristics. Therefore, the aim of this study was to develop a validated method to characterise the viscoelastic properties of soft tissues based on ultrasound elastography data.. Plantar soft tissue was chosen as the tissue of interest, and gelatine-phantoms replicating its mechanical properties were manufactured for validation of the protocol. Both plantar soft tissue and the phantom were scanned using Reverberant shear wave ultrasound (US) elastography at 400-600 Hz. Shear wave speed was estimated using the US particle velocity data. The viscoelastic parameters were extracted by fitting the Young's modulus as a function of frequency derived from the constitutive equations of the eight rheological models (four classic and their fractional-derivative versions) to the shear wave dispersion data. Furthermore, stress-time functions derived from the eight rheological models were fitted to the phantom stress-relaxation data.. The viscoelastic parameters estimated using elastography data based on the fractional-derivative (FD) models, compared to the classic models, were closer to those quantified using the mechanical test. In addition, the FD-Maxwell and FD-Kelvin-Voigt models showed to more effectively replicate the viscoelastic behaviour of the plantar soft tissue with minimum number of model parameters (R2= 0.72 for both models) . Hence the FD-KV and FD-Maxwell models can more effectively quantify the viscoelastic characteristics of the soft tissue compared to other models.. In this study, a method for mechanical characterisation of the viscoelastic properties of soft tissue in ultrasound elastography was developed and fully validated. An investigation into the most valid rheological model and its applications in plantar soft tissue assessment were also presented. This proposed approach for the characterisation of viscous and elastic mechanical properties of soft tissue has implications in assessing the soft tissue function where those can be used as markers for diagnosis or prognosis of tissue status.
软组织的力学行为受其弹性和粘性特性的影响。因此，本研究旨在开发一种基于超声弹性成像数据的方法来验证软组织的粘弹性特性。选择足底软组织作为研究对象，并制造了模仿其机械性能的明胶模型进行验证。使用 Reverberant shear wave ultrasound (US) 弹性成像技术在 400-600 Hz 下对足底软组织和模型进行扫描。使用 US 粒子速度数据估计剪切波速度。通过将本构方程中推导出的杨氏模量作为频率的函数拟合到剪切波频散数据中，从八个流变模型（四个经典模型及其分数导数版本）中提取粘弹性参数。此外，从八个流变模型推导出的应力-时间函数拟合到模型的应力松弛数据。与经典模型相比，基于分数导数（FD）模型的弹性成像数据估计的粘弹性参数更接近使用机械测试量化的值。此外，FD-Maxwell 和 FD-Kelvin-Voigt 模型在使用最小数量的模型参数（两个模型的 R2=0.72）更有效地复制足底软组织的粘弹性行为方面表现出更好的效果。因此，与其他模型相比，FD-KV 和 FD-Maxwell 模型可以更有效地量化软组织的粘弹性特性。在这项研究中，开发了一种在超声弹性成像中对软组织粘弹性特性进行机械特性分析的方法，并进行了全面验证。还对最有效的流变模型及其在足底软组织评估中的应用进行了研究。本研究提出的软组织粘性和弹性力学特性的表征方法在评估软组织功能方面具有重要意义，因为这些特性可以作为诊断或预测组织状态的标志物。
