Romijn R L, Thijssen J M, van Beuningen G J
Inst. of Ophthalmology, Nijmegen Univ.
IEEE Trans Ultrason Ferroelectr Freq Control. 1989;36(6):593-606. doi: 10.1109/58.39109.
The reliability of the estimation of the size of scattering structures is assessed by realistic simulations and phantom experiments. The acoustic tissue model used in the simulation studies comprised a constant sound speed, homogeneous attenuation, and isotropic scattering. The scattering models considered were a discrete (spherical) model and two inhomogeneous-continuum models. The latter were characterized by an exponential and a Gaussian autocorrelation function, respectively. The backscattering spectra were, over the range from 5 to 10 MHz, fitted to linear, power, and autocorrelation functions of the three scattering models. The effects of the fitting function, the attenuation-either in an intervening layer or within the region of interest (ROI)-of the transmission pulse, and a spread in the scatterer sizes on the accuracy and the precision of the size estimates were assessed. The attenuation in the intervening tissue layer(s) as well as in the ROI itself has a significant effect on the accuracy of the size estimates and needs to be corrected. When performing the attenuation correction the inaccuracy of the attenuation estimate of the intervening layer leads to a large bias in the estimated scatterer size. Experimental results support the conclusion that scatterer size is a feasible tissue characterization parameter.
通过实际模拟和体模实验评估散射结构尺寸估计的可靠性。模拟研究中使用的声学组织模型包括恒定声速、均匀衰减和各向同性散射。考虑的散射模型有离散（球形）模型和两个非均匀连续体模型。后者分别由指数自相关函数和高斯自相关函数表征。在5至10MHz范围内，将后向散射光谱拟合到三种散射模型的线性、幂函数和自相关函数。评估了拟合函数、透射脉冲在中间层或感兴趣区域（ROI）内的衰减以及散射体尺寸的分散对尺寸估计的准确性和精度的影响。中间组织层以及ROI本身的衰减对尺寸估计的准确性有显著影响，需要进行校正。在进行衰减校正时，中间层衰减估计的不准确性会导致估计的散射体尺寸出现较大偏差。实验结果支持散射体尺寸是一个可行的组织表征参数这一结论。
