Zagzebski J A, Chen J F, Dong F, Wilson T
Department of Medical Physics, University of Wisconsin, Madison, WI 53706, USA.
IEEE Trans Ultrason Ferroelectr Freq Control. 1999;46(1):35-40. doi: 10.1109/58.741421.
Previous studies show that first-order statistical properties of ultrasound echo signals are related to the effective number of scatterers in the "resolution cell" of a pulse-echo ultrasound system. When the effective number of scatterers is large (~10 or more) this results in echo signals whose amplitude follows a Rayleigh distribution, with the RF echo signal obeying Gaussian statistics; deviation from Rayleigh or Gaussian statistics yields information on scatterer number densities. In this paper, the influence of the medium's attenuation on non-Gaussian properties of the echo signal is considered. Preferential attenuation of higher frequency components of a pulsed ultrasound beam effectively broadens the beam and increases the resolution cell size. Thus, the resultant non-Gaussian parameter for broad bandwidth excitation of the transducer depends not only on the scatterer number density but also on the attenuation in the medium. These effects can be reduced or eliminated by using narrow-band experiments.
先前的研究表明，超声回波信号的一阶统计特性与脉冲回波超声系统“分辨单元”内散射体的有效数量有关。当散射体的有效数量较大（约10个或更多）时，这会导致回波信号的幅度遵循瑞利分布，射频回波信号服从高斯统计；偏离瑞利或高斯统计会产生关于散射体数量密度的信息。在本文中，考虑了介质衰减对回波信号非高斯特性的影响。脉冲超声束高频成分的优先衰减有效地拓宽了波束并增大了分辨单元尺寸。因此，换能器宽带激发产生的非高斯参数不仅取决于散射体数量密度，还取决于介质中的衰减。通过使用窄带实验可以减少或消除这些影响。
