Rouze Ned C, Deng Yufeng, Palmeri Mark L, Nightingale Kathryn R
Biomedical Engineering, Duke University, Durham, North Carolina, USA.
Biomedical Engineering, Duke University, Durham, North Carolina, USA.
Ultrasound Med Biol. 2017 Oct;43(10):2500-2506. doi: 10.1016/j.ultrasmedbio.2017.06.006. Epub 2017 Jul 19.
Recent measurements of shear wave propagation in viscoelastic materials have been analyzed by constructing the 2-D Fourier transform (2DFT) of the shear wave signal and measuring the phase velocity c(ω) and attenuation α(ω) from the peak location and full width at half-maximum (FWHM) of the 2DFT signal at discrete frequencies. However, when the shear wave is observed over a finite spatial range, the 2DFT signal is a convolution of the true signal and the observation window, and measurements using the FWHM can yield biased results. In this study, we describe a method to account for the size of the spatial observation window using a model of the 2DFT signal and a non-linear, least-squares fitting procedure to determine c(ω) and α(ω). Results from the analysis of finite-element simulation data agree with c(ω) and α(ω) calculated from the material parameters used in the simulation. Results obtained in a viscoelastic phantom indicate that the measured attenuation is independent of the observation window and agree with measurements of c(ω) and α(ω) obtained using the previously described progressive phase and exponential decay analysis.
近期对粘弹性材料中剪切波传播的测量分析，是通过构建剪切波信号的二维傅里叶变换（2DFT），并在离散频率下从2DFT信号的峰值位置和半高宽（FWHM）测量相速度c(ω)和衰减α(ω)来进行的。然而，当在有限空间范围内观察剪切波时，2DFT信号是真实信号与观测窗口的卷积，使用FWHM进行测量可能会产生有偏差的结果。在本研究中，我们描述了一种方法，使用2DFT信号模型和非线性最小二乘拟合程序来考虑空间观测窗口的大小，以确定c(ω)和α(ω)。有限元模拟数据分析结果与根据模拟中使用的材料参数计算得到的c(ω)和α(ω)一致。在粘弹性体模中获得的结果表明，测量得到的衰减与观测窗口无关，并且与使用先前描述的渐进相位和指数衰减分析获得的c(ω)和α(ω)测量结果一致。
