IEEE Trans Ultrason Ferroelectr Freq Control. 2018 Jan;65(1):30-38. doi: 10.1109/TUFFC.2017.2773495.
The focused transmit beam is a standard tool for clinical ultrasound scanning, concentrating energy from a number of array elements toward an imaging target. However, above and below the transmit focus, much of the energy in the beam is spread in a broadened main lobe and long off-axis tails that are ignored by conventional beamforming methods. This paper proposes a method to decompose a set of focused transmit beams into their constituent components-diverging waves from individual array elements. The recovery of this complete data set enables synthetic transmit focusing at all points in the field of view without beam shape or focal depth artifacts commonly associated with virtual source synthetic aperture beamforming. An efficient frequency-domain linear decoding implementation is introduced. The principles of the method are demonstrated both in transmit field simulations and experimental imaging. At depth, up to a 9.6-dB improvement in electronic signal-to-noise ratio and 8.9-dB improvement in contrast were observed in comparison with conventional dynamic receive beamforming. The proposed method is broadly applicable to existing scan sequences and requires only channel data for processing.
聚焦发射波束是临床超声扫描的标准工具，它将来自多个阵列元件的能量集中到成像目标上。然而，在发射焦点的上方和下方，波束中的大部分能量在扩展的主瓣和长轴外尾部中扩散，这些能量被传统的波束形成方法忽略了。本文提出了一种将一组聚焦发射波束分解为其组成部分的方法，即来自各个阵列元件的发散波。恢复这个完整的数据集可以在视场中的所有点进行合成发射聚焦，而不会出现与虚拟源合成孔径波束形成相关的波束形状或焦点深度伪影。引入了一种高效的频域线性解码实现方法。该方法的原理在发射场模拟和实验成像中都得到了验证。在深度上，与传统的动态接收波束形成相比，电子信噪比提高了 9.6dB，对比度提高了 8.9dB。所提出的方法广泛适用于现有的扫描序列，并且仅需要通道数据进行处理。
