Department of Physics, University of Kuopio, Kuopio, Finland.
IEEE Trans Ultrason Ferroelectr Freq Control. 2010 Apr;57(4):892-9. doi: 10.1109/TUFFC.2010.1493.
Quantitative high-frequency ultrasonic evaluation of articular cartilage has shown a potential for the diagnosis of osteoarthritis, where the roughness of the surface, collagen and proteoglycan contents, and the density and mechanical properties of cartilage change concurrently. Experimentally, these factors are difficult to investigate individually and thus a numerical model is needed. The present study is the first one to use finite difference time domain modeling of pulse-echo measurements of articular cartilage. Ultrasound reflection from the surface was investigated with varying surface roughness, material parameters (Young's modulus, density, longitudinal, and transversal velocities) and inclination of the samples. The 2-D simulation results were compared with the results from experimental measurements of the same samples in an identical geometry. Both the roughness and the material parameters contributed significantly to the ultrasound reflection. The angular dependence of the ultrasound reflection was strong for a smooth cartilage surface but disappeared for the samples with a rougher surface. These results support the findings of previous experimental studies and indicate that ultrasound detects changes in the cartilage that are characteristic of osteoarthritis. In the present study there are differences between the results of the simulations and the experimental measurements. However, the systematic patterns in the experimental behavior are correctly reproduced by the model. In the future, our goal is to develop more realistic acoustic models incorporating inhomogeneity and anisotropy of the cartilage.
高频超声定量评估关节软骨已显示出在骨关节炎诊断方面的潜力，其中表面粗糙度、胶原和蛋白聚糖含量以及软骨的密度和力学性能同时发生变化。在实验中，这些因素很难单独研究，因此需要建立数值模型。本研究首次使用脉冲回波测量关节软骨的有限差分时间域建模。通过改变表面粗糙度、材料参数（杨氏模量、密度、纵波和横波速度）和样品倾斜度，研究了来自表面的超声反射。将 2D 模拟结果与相同几何形状的相同样品的实验测量结果进行了比较。粗糙度和材料参数都对超声反射有显著影响。对于光滑的软骨表面，超声反射的角度依赖性很强，但对于更粗糙的表面，这种依赖性消失了。这些结果支持了先前的实验研究结果，并表明超声检测到了骨关节炎特有的软骨变化。在本研究中，模拟结果与实验测量结果之间存在差异。然而，模型正确地再现了实验行为中的系统模式。未来，我们的目标是开发更现实的声学模型，纳入软骨的非均质性和各向异性。
