Lavarello Roberto J, Oelze Michael L
Department of Electrical and Computer Engineering, Bioacoustics Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
J Acoust Soc Am. 2009 Feb;125(2):793-802. doi: 10.1121/1.3050249.
Inverse scattering is considered one of the most robust and accurate ultrasonic tomography methods. Most inverse scattering formulations neglect density changes in order to reconstruct sound speed and acoustic attenuation. Some studies available in literature suggest that density distributions can also be recovered using inverse scattering formulations. Two classes of algorithms have been identified. (1) The separation of sound speed and density contributions from reconstructions using constant density inverse scattering algorithms at multiple frequencies. (2) The inversion of the full wave equation including density changes. In this work, the performance of a representative algorithm for each class has been studied for the reconstruction of circular cylinders: the dual frequency distorted Born iterative method (DF-DBIM) and the T-matrix formulation. Root mean square error values lower than 30% were obtained with both algorithms when reconstructing cylinders up to eight wavelengths in diameter with moderate density changes. However, in order to provide accurate reconstructions the DF-DBIM and T-matrix method required very high signal-to-noise ratios and significantly large bandwidths, respectively. These limitations are discussed in the context of practical experimental implementations.
逆散射被认为是最稳健和准确的超声层析成像方法之一。大多数逆散射公式为了重建声速和声学衰减而忽略密度变化。文献中的一些研究表明，密度分布也可以使用逆散射公式来恢复。已经确定了两类算法。（1）在多个频率下使用恒定密度逆散射算法从重建中分离出声速和密度贡献。（2）对包括密度变化的全波动方程进行反演。在这项工作中，针对每一类的一种代表性算法对圆柱体重建的性能进行了研究：双频扭曲玻恩迭代法（DF-DBIM）和T矩阵公式。当重建直径达八个波长且密度变化适中的圆柱体时，两种算法均获得了低于30%的均方根误差值。然而，为了提供准确的重建，DF-DBIM和T矩阵方法分别需要非常高的信噪比和显著大的带宽。在实际实验实施的背景下讨论了这些限制。
