IEEE Trans Ultrason Ferroelectr Freq Control. 2017 Oct;64(10):1439-1449. doi: 10.1109/TUFFC.2017.2725839. Epub 2017 Jul 11.
Shear-wave elasticity imaging (SWEI) enables the quantitative assessment of the mechanical properties of tissue. In SWEI, the effective generation of acoustic radiation force is of paramount importance. Consequently, several research groups have investigated various transmit beamforming and pulse-sequencing methods. To further improve the efficiency of the shear-wave generation, and therefore, to increase the quality of SWEI, we introduce a technique referred to as "multiangle compound SWEI" (MAC-SWEI), which uses simultaneous multiangular push beams created by dual-phase transmit focusing. By applying a constant phase offset on every other element of an array transducer, dual-phase transmit focusing creates both main and grating lobes (i.e., multiangular push beams for pushing) to simultaneously generate shear waves with several wavefront angles. The shear waves propagating at different angles are separated by multidirectional filtering in the frequency domain, leading to the reconstruction of multiple spatially co-registered shear-wave velocity maps. To form a single-elasticity image, these maps are combined, while regions associated with known artifacts created by the push beams are omitted. Overall, we developed and tested the MAC-SWEI method using Field II quantitative simulations and the experiments performed using a programmable ultrasound imaging system. Our results suggest that MAC-SWEI with dual-phase transmit focusing may improve the quality of elasticity maps.
剪切波弹性成像（SWEI）可实现组织力学特性的定量评估。在 SWEI 中，声辐射力的有效产生至关重要。因此，有几个研究小组研究了各种发射波束形成和脉冲序列方法。为了进一步提高剪切波产生的效率，从而提高 SWEI 的质量，我们引入了一种称为“多角度复合 SWEI”（MAC-SWEI）的技术，该技术使用双相位发射聚焦产生的同时多角度推波。通过在阵列换能器的每个偶数元件上施加恒定的相位偏移，双相位发射聚焦产生主瓣和栅瓣（即用于推波的多角度推波），从而同时产生具有多个波前角的剪切波。在频域中通过多方向滤波分离以不同角度传播的剪切波，从而重建多个空间上配准的剪切波速度图。为了形成单个弹性图像，将这些图组合在一起，同时忽略与推波束产生的已知伪影相关的区域。总体而言，我们使用 Field II 定量模拟和使用可编程超声成像系统进行的实验开发并测试了 MAC-SWEI 方法。我们的结果表明，具有双相位发射聚焦的 MAC-SWEI 可能会提高弹性图的质量。
