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Adaptive imaging using the generalized coherence factor

机译：使用广义相干因子的自适应成像

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Sound-velocity inhomogeneities degrade both spatial and contrast resolutions. This paper proposes a new adaptive imaging technique that uses the generalized coherence factor (GCF) to reduce the focusing errors resulting from the sound-velocity inhomogeneities. The GCF is derived from the spatial spectrum of the received aperture data after proper receive delays have been applied. It is defined as the ratio of the spectral energy within a prespecified low-frequency range to the total energy. It is demonstrated that the low-frequency component of the spectrum corresponds to the coherent portion of the received data, and that the high-frequency component corresponds to the incoherent portion. Hence, the GCF reduces to the coherence factor defined in the literature if the prespecified low-frequency range is restricted to DC only. In addition, the GCF is also an index of the focusing quality and can be used as a weighting factor for the reconstructed image. The efficacy of the GCF technique is demonstrated for focusing errors resulting from the sound-velocity inhomogeneities. Simulations and real ultrasound data are used to evaluate the efficacy of the proposed GCF technique. The characteristics of the GCF, including the effects of the signal-to-noise ratio and the number of channels, are also discussed. The GCF technique also is compared with the correlation-based technique and the parallel adaptive receive compensation algorithm; the improvement in image quality obtained with the proposed technique rivals that of the latter technique. In the presence of a displaced phase screen, this proposed technique also outperforms the correlation-based technique. Computational complexity and implementation issues also are addressed.
机译：声速不均匀会降低空间分辨率和对比度分辨率。本文提出了一种新的自适应成像技术，该技术使用广义相干因子（GCF）来减少声速不均匀性引起的聚焦误差。在应用了适当的接收延迟之后，从接收的孔径数据的空间频谱中得出GCF。它定义为在预定的低频范围内的频谱能量与总能量之比。证明了频谱的低频分量对应于接收数据的相干部分，而高频分量对应于非相干部分。因此，如果将预定的低频范围限制为仅DC，则GCF会降低到文献中定义的相干因子。另外，GCF也是聚焦质量的指标，并且可以用作重建图像的加权因子。事实证明，GCF技术可有效解决因声速不均匀而引起的聚焦误差。仿真和实际超声数据用于评估提出的GCF技术的功效。还讨论了GCF的特性，包括信噪比和通道数的影响。 GCF技术也与基于相关的技术和并行自适应接收补偿算法进行了比较。所提出的技术所获得的图像质量的改进与后一种技术相抗衡。在存在相位偏移屏幕的情况下，该提议的技术也优于基于相关的技术。还解决了计算复杂性和实现问题。

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