Duncan David P, Astheimer Jeffrey P, Waag Robert C
Department of Electrical and Computer Engineering, University of Rochester, Rochester, New York 14627, USA.
J Acoust Soc Am. 2009 May;125(5):3101-19. doi: 10.1121/1.3097497.
Pressure scattered by cylindrical and spherical objects with elevation-focused illumination and reception has been analytically calculated, and corresponding cross sections have been reconstructed with a two-dimensional algorithm. Elevation focusing was used to elucidate constraints on quantitative imaging of three-dimensional objects with two-dimensional algorithms. Focused illumination and reception are represented by angular spectra of plane waves that were efficiently computed using a Fourier interpolation method to maintain the same angles for all temporal frequencies. Reconstructions were formed using an eigenfunction method with multiple frequencies, phase compensation, and iteration. The results show that the scattered pressure reduces to a two-dimensional expression, and two-dimensional algorithms are applicable when the region of a three-dimensional object within an elevation-focused beam is approximately constant in elevation. The results also show that energy scattered out of the reception aperture by objects contained within the focused beam can result in the reconstructed values of attenuation slope being greater than true values at the boundary of the object. Reconstructed sound speed images, however, appear to be relatively unaffected by the loss in scattered energy. The broad conclusion that can be drawn from these results is that two-dimensional reconstructions require compensation to account for uncaptured three-dimensional scattering.
通过柱面和球面物体在仰角聚焦照明和接收下散射的压力已通过解析计算得出，并且相应的截面已使用二维算法进行重建。仰角聚焦用于阐明二维算法对三维物体定量成像的限制。聚焦照明和接收由平面波的角谱表示，使用傅里叶插值方法有效地计算这些角谱，以确保所有时间频率的角度相同。使用具有多个频率、相位补偿和迭代的本征函数方法进行重建。结果表明，散射压力简化为二维表达式，当三维物体在仰角聚焦光束内的区域在仰角上近似恒定时，二维算法适用。结果还表明，聚焦光束内物体散射出接收孔径的能量会导致重建的衰减斜率值在物体边界处大于真实值。然而，重建的声速图像似乎相对不受散射能量损失的影响。从这些结果可以得出的广泛结论是，二维重建需要进行补偿以考虑未捕获的三维散射。
