Liu D L, Waag R C
Department of Electrical Engineering, University of Rochester, New York 14627, USA.
J Acoust Soc Am. 1997 Feb;101(2):1172-83. doi: 10.1121/1.418025.
The amplitude characteristics of ultrasonic wavefront distortion produced by transmission through the abdominal wall and breast is described. Ultrasonic pulses were recorded in a two-dimensional aperture after transmission through specimens of abdominal wall or breast. After the pulse arrival times were corrected for geometric path differences, the pulses were temporally Fourier transformed and two-dimensional maps of harmonic amplitudes in the measurement aperture were computed. The results indicate that, as the temporal frequency increases, the fluctuation in harmonic amplitudes increases but the spatial scale of the fluctuation decreases. The normalized second-order and third-order moments of the amplitude distribution also increase with temporal frequency. The wide range variation of these distribution characteristics could not be covered by the Rayleigh, Rician, or K-distribution because of their limited flexibility. However, the Weibull distribution and especially the generalized K-distribution provide better fits to the data. In the fit of the generalized K-distribution, a decrease of its parameter alpha with increasing temporal frequency was observed, as predicted by analysis based on a phase screen model.
描述了超声波通过腹壁和乳腺传播时产生的波前畸变的幅度特性。在超声波通过腹壁或乳腺标本传播后，在二维孔径中记录超声波脉冲。在对脉冲到达时间进行几何路径差异校正后，对脉冲进行时间傅里叶变换，并计算测量孔径中谐波幅度的二维图。结果表明，随着时间频率的增加，谐波幅度的波动增加，但波动的空间尺度减小。幅度分布的归一化二阶和三阶矩也随时间频率增加。由于瑞利分布、莱斯分布或K分布的灵活性有限，无法涵盖这些分布特性的广泛变化。然而，威布尔分布，特别是广义K分布能更好地拟合数据。在广义K分布的拟合中，如基于相位屏模型的分析所预测的，观察到其参数α随时间频率增加而减小。
