Bae Sua, Kim Pilsu, Song Tai-Kyong
Department of Electronic Engineering, Sogang University, Seoul 04107, Republic of Korea.
J Acoust Soc Am. 2018 Nov;144(5):2627. doi: 10.1121/1.5065391.
Synthetic transmit focusing (STF) methods using unfocused waves or plane waves (PWs) have recently been investigated extensively. However, STF using PWs with a convex array (PWSTF-CA) has not been rigorously studied for high-resolution sector imaging. In this paper, the authors suggest an analytical model for accurate characterization of the spatial beam patterns of PWSTF-CA using a large range of either uniformly or non-uniformly distributed PW angles. On the basis of the model, a frame-based PWSTF-CA approach with non-uniform PW angles is suggested to achieve superior image quality at a higher frame rate than conventional transmit focusing (CTF). The analytical model can also be used for optimal selection of a set of PW angles to scan the entire sectorial field of view and its subsets employed for STF at each imaging point. The authors also investigate how to select transmit subarrays for each of the PWs to obtain the best spatial resolution. A theoretical analysis and simulations are conducted for the verification of the analytical model and the optimal utilization strategy of PWSTF-CA. The results indicate that the PWSTF-CA improves not only the frame rate but also the contrast, signal-to-noise ratio, and resolution compared with the CTF, as in the case of PWSTF with linear arrays.
近年来，使用非聚焦波或平面波（PW）的合成发射聚焦（STF）方法得到了广泛研究。然而，对于高分辨率扇形成像，使用凸阵的平面波合成发射聚焦（PWSTF-CA）尚未得到严格研究。在本文中，作者提出了一种分析模型，用于精确表征使用大范围均匀或非均匀分布的PW角度的PWSTF-CA的空间波束方向图。基于该模型，提出了一种具有非均匀PW角度的基于帧的PWSTF-CA方法，以在比传统发射聚焦（CTF）更高的帧率下实现卓越的图像质量。该分析模型还可用于优化选择一组PW角度，以扫描整个扇形视野及其在每个成像点用于STF的子集。作者还研究了如何为每个PW选择发射子阵列以获得最佳空间分辨率。进行了理论分析和仿真，以验证该分析模型和PWSTF-CA的最佳利用策略。结果表明，与CTF相比，PWSTF-CA不仅提高了帧率，还提高了对比度、信噪比和分辨率，与线性阵列的PWSTF情况相同。
