Robust finite impulse response beamforming applied to medical ultrasound.
Robust finite impulse response beamforming applied to medical ultrasound.
复制标题
DOI：
10.1109/tuffc.2009.1159
复制
发表时间：
2009-06
期刊：
影响因子：
--
通讯作者：
Walker WF
中科院分区：
文献类型：
--
作者：
Guenther DA;Walker WF
我们之前描述了一种波束形成器架构，该架构用通道独特的有限脉冲响应 (FIR) 滤波器取代每个接收通道上的单个变迹权重。滤波器权重旨在优化成像系统的对比度分辨率性能。虽然 FIR 波束形成器在对比度分辨率方面提供了显着的增益，但波束形成器的灵敏度较低，并且在存在噪声的情况下其性能会迅速下降。本文提出了一种新方法来提高 FIR 波束形成器对电子噪声以及阵列响应变化或不确定性的鲁棒性。还描述了一种方法，该方法通过在滤波器设计算法中应用任意加权函数来控制 FIR 波束形成器空间响应的旁瓣电平。使用广义囊胞分辨率指标对稳健的 FIR 波束形成器进行分析，该指标将波束形成器的临床成像性能量化为囊肿大小和通道输入信噪比 (SNR) 的函数。对两种鲁棒 FIR 波束形成器（动态聚焦 FIR (DF-FIR) 波束形成器和群聚焦 FIR (GF-FIR) 波束形成器）、传统延迟求和 (DAS) 波束形成器和空间匹配滤波器 (SMF) 波束形成器之间的基本性能限制进行了比较。这项研究的结果表明，与最佳对比度分辨率 FIR 波束形成器相比，新型 DF- 和 GF-FIR 波束形成器对电子噪声的鲁棒性更强。此外，增加的稳健性只会导致囊性分辨率的轻微损失。广义囊性分辨率指标的结果表明，9 抽头鲁棒 FIR 波束形成器优于 SMF 和 DAS 波束形成器，直到接收通道输入 SNR 降至 -5 dB 以下；而 9 抽头最佳对比度分辨率波束形成器的性能会下降约 50 dB SNR。在稳健的 FIR 波束形成器上研究了中等相位像差的影响，其特征是先验均方根强度为 28 ns，先验半高相关长度为 3.6 mm。全套稳健的 FIR 波束形成滤波器权重是使用 Ultrasonix Sonix RP 扫描仪的计算机模型和 L14-5/38mm 探头构建的。使用导出的权重，生成一系列模拟点目标和消声囊肿 B 模式图像，以进一步研究使用鲁棒 FIR 波束形成器时对比度分辨率的潜在增加。在研究条件下，与传统 DAS 波束形成器相比，7 抽头最佳对比度分辨率波束形成器和添加了 SNR 约束的 7 抽头稳健波束形成器分别将病变可检测性提高了 247% 和 137%。最后，使用这种新颖的接收架构生成实验体模和活体图像。与传统的波束形成图像相比，模拟和实验图像清楚地显示杂波减少和对比度分辨率增加。这种新颖的接收波束形成器可以应用于任何传统的超声系统，其中系统响应具有相当好的特征。
We previously described a beamformer architecture that replaces the single apodization weights on each receive channel with channel-unique finite impulse response (FIR) filters. The filter weights are designed to optimize the contrast resolution performance of the imaging system. While the FIR beamformer offers significant gains in contrast resolution, the beamformer suffers from low sensitivity and its performance rapidly degrades in the presence of noise. In this paper a new method is presented to improve the robustness of the FIR beamformer to electronic noise as well as variation or uncertainty in the array response. A method is also described, which controls the sidelobe levels of the FIR beamformer’s spatial response by applying an arbitrary weighting function in the filter design algorithm. The robust FIR beamformer is analyzed using a generalized cystic resolution metric that quantifies a beamformer’s clinical imaging performance as a function of cyst size and channel input signal-to-noise ratio (SNR). Fundamental performance limits are compared between two robust FIR beamformers (the dynamic focus FIR (DF-FIR) beamformer and the group focus FIR (GF-FIR) beamformer), the conventional delay-and-sum (DAS) beamformer, and the spatial matched filter (SMF) beamformer. Results from this study show that the new DF- and GF-FIR beamformers are more robust to electronic noise compared to the optimal contrast resolution FIR beamformer. Furthermore, the added robustness only comes with a slight loss in cystic resolution. Results from the generalized cystic resolution metric show that a 9-tap robust FIR beamformer outperforms the SMF and DAS beamformer until receive channel input SNR drops below −5 dB; whereas, the 9-tap optimal contrast resolution beamformer’s performance deteriorates around 50 dB SNR. The effects of moderate phase aberrations, characterized by an a priori root-mean-square strength of 28 ns and an a priori full-width at half-maximum correlation length of 3.6 mm, are investigated on the robust FIR beamformers. Full sets of robust FIR beamformer filter weights are constructed using an in silico model of the Ultrasonix Sonix RP scanner and the L14-5/38mm probe. Using the derived weights a series of simulated point target and anechoic cyst B-mode images are generated to further investigate the potential increases in contrast resolution when using the robust FIR beamformers. Under the investigated conditions, the 7-tap optimal contrast resolution beamformer and the 7-tap robust beamformer with added SNR constraint increase lesion detectability by 247% and 137% compared to the conventional DAS beamformer, respectively. Finally experimental phantom and in vivo images are produced using this novel receive architecture. The simulated and experimental images clearly show a reduction in clutter and an increase in contrast resolution compared to the conventionally beamformed images. This novel receive beamformer can be applied to any conventional ultrasound system where the system response is reasonably well characterized.