Yen Jesse T, Nguyen Man Minh, Lou Yang, Shin Jun S, Chen Yuling, Tarnoff Harry L
IEEE Trans Ultrason Ferroelectr Freq Control. 2021 Jun;68(6):2183-2192. doi: 10.1109/TUFFC.2021.3062850. Epub 2021 May 25.
Low-cost ultrasound imaging systems are desired for many applications outside of radiology and cardiology departments. By making ultrasound systems smaller and lower cost, the use of ultrasound has spread from these mainstays to other areas of the hospital such as emergency departments and critical care. To further miniaturize and reduce the cost of ultrasound systems, we have investigated novel Fresnel-based beamforming methods to reduce front-end hardware requirements. Previous studies with linear and curvilinear arrays demonstrated comparable imaging performance using Fresnel-based beamforming versus delay-and-sum (DAS) beamforming. In this work, we extend Fresnel-based beamforming to phased arrays with beam steering. To accomplish this in transmit mode, we introduce a technique called a gated transmit beamformer where multicycle bursts are gated using multiplexers. In receive mode, a 64-element 2.5-MHz phased array is broken up into four 16-element subapertures, and each subaperture performs Fresnel beamforming before a final beamforming step is done. Timing errors are inevitable with Fresnel-based beamforming leading to higher sidelobe and clutter levels. To suppress sidelobe and clutter contributions, we also combine this with our previous technique, dual apodization with cross correlation (DAX) to improve contrast. Field II simulations are performed to evaluate spatial resolution and contrast-to-noise ratio and compared to standard DAS beamforming. Fresnel-based and gated transmit beamforming is also implemented using synthetic aperture data from tissue-mimicking phantoms. Lastly, a hardware proof-of-concept (PoC) Fresnel beamformer was designed, assembled, and evaluated with images from tissue-mimicking phantoms and initial in vivo images.
放射科和心脏病科之外的许多应用都需要低成本的超声成像系统。通过使超声系统体积更小、成本更低，超声的应用已从这些主要领域扩展到医院的其他科室，如急诊科和重症监护室。为了进一步使超声系统小型化并降低成本，我们研究了基于菲涅耳的新型波束形成方法，以减少前端硬件需求。先前对线性和曲线阵列的研究表明，基于菲涅耳的波束形成与延迟求和（DAS）波束形成相比，具有相当的成像性能。在这项工作中，我们将基于菲涅耳的波束形成扩展到具有波束控制的相控阵。为了在发射模式下实现这一点，我们引入了一种称为门控发射波束形成器的技术，其中多周期脉冲串通过多路复用器进行门控。在接收模式下，一个64阵元、2.5MHz的相控阵被分成四个16阵元的子阵元，每个子阵元在完成最终波束形成步骤之前执行菲涅耳波束形成。基于菲涅耳的波束形成不可避免地会产生定时误差，从而导致更高的旁瓣和杂波水平。为了抑制旁瓣和杂波的影响，我们还将其与我们之前的技术——互相关双窗加权（DAX）相结合，以提高对比度。进行了Field II模拟，以评估空间分辨率和对比噪声比，并与标准DAS波束形成进行比较。基于菲涅耳的和门控发射波束形成也使用来自仿组织体模的合成孔径数据来实现。最后，设计、组装了一个硬件概念验证（PoC）菲涅耳波束形成器，并使用来自仿组织体模的图像和初始体内图像进行了评估。
