Zhu Q, Steinberg B D
Valley Forge Research Center, Moore School of Electrical Engineering, University of Pennsylvania, Philadelphia 19104.
J Acoust Soc Am. 1994 Jul;96(1):1-9. doi: 10.1121/1.410466.
Ultrasound measurements of a large population of wavefronts transmitted through female breasts at 3 and 4 MHz show that the wavefront amplitude distribution is close to Rayleigh. This finding is consistent with a fully developed scatter field, implying that the scatter energy removed from the coherent incident beam dominates the wavefront. The wavefront received from an inhomogeneous medium is the superposition of an incident wave plus a scattered wave. If the scattered field is weak, the received field is dominated by the incident field and the wavefront amplitude distribution is Rician. If the scattered field is strong, the received field is primarily the scattered field and the wavefront amplitude distribution is Rayleigh. If, in addition to scattering, refraction between bodies of different refractive indexes occurs, the total net effect on the wavefront amplitude distribution is the same as for strong scattering. This is what we have observed in the highly refractive female breast. This result has implications for the design of high lateral-resolution echo scanners that will incorporate adaptive phase deaberration algorithms. The published algorithms were developed for weak scattering and therefore may not be powerful enough. Alternatives have to be found to deaberrate the severe wavefront distortion in the breast.
对大量在3兆赫和4兆赫频率下透过女性乳房传播的波前进行超声测量表明，波前振幅分布接近瑞利分布。这一发现与充分发展的散射场一致，意味着从相干入射光束中移除的散射能量主导了波前。从不均匀介质接收到的波前是入射波加上散射波的叠加。如果散射场较弱，接收到的场由入射场主导，波前振幅分布为莱斯分布。如果散射场较强，接收到的场主要是散射场，波前振幅分布为瑞利分布。此外，如果除了散射之外，不同折射率的物体之间发生折射，对波前振幅分布的总净效应与强散射相同。这就是我们在高折射率的女性乳房中所观察到的。这一结果对将采用自适应相位去像差算法的高横向分辨率回波扫描仪的设计具有启示意义。已发表的算法是针对弱散射开发的，因此可能不够强大。必须找到替代方法来消除乳房中严重的波前畸变。
