Agarwal Anup, Schneider Fabio Kurt, Yoo Yang Mo, Kim Yongmin
Departments of Electrical Engineering and Bioengineering, Image Computing Systems Laboratory, University of Washington, Seattle, WA, USA.
IEEE Trans Ultrason Ferroelectr Freq Control. 2008 Sep;55(9):1947-55. doi: 10.1109/TUFFC.886.
Over the last few decades, dynamic focusing based on digital receive beamforming (DRBF) has led to significant improvements in image quality. However, it is computationally very demanding due to its requirement for multiple lowpass filters (e.g., a complex filter for each receive channel in quadrature demodulation-based phase rotation beamformers (QD-PRBF)). We recently developed a novel phase rotation beamformer with reduced complexity, which can lower: 1) the number of lowpass filters using 2-stage demodulation (TSD) and 2) the number of beamforming points using adap tive field-of-view (AFOV) imaging. In TSD, dynamic focusing is performed on the mixed signals, while sampling frequency of the beamformed signal (i.e., beamforming frequency) is adjusted based on the displayed field-of-view (FOV) size in AFOV imaging. In this paper, the image quality of the developed beamformer (i.e., TSD-AFOV-PRBF) has been quantitatively evaluated using phantom and in vivo data. From the phantom study, it was found that TSD-AFOV-PRBF with only 1024 beamforming points provides comparable image quality to QD-PRBF. We obtained a median contrast resolution (CR) degradation of 7.6% for the FOV size of 160 mm. Image quality steadily improves with FOV size reduction (e.g., 2.3% CR degradation at 85 mm). Similar results were also obtained from an in vivo study. Thus, TSD-AFOV-PRBF could provide comparable image quality to conventional beamformers at considerably reduced computational cost.
在过去几十年中，基于数字接收波束形成（DRBF）的动态聚焦显著提高了图像质量。然而，由于其需要多个低通滤波器（例如，基于正交解调的相位旋转波束形成器（QD-PRBF）中每个接收通道都需要一个复数滤波器），其计算量非常大。我们最近开发了一种复杂度降低的新型相位旋转波束形成器，它可以降低：1）使用两级解调（TSD）的低通滤波器数量，以及2）使用自适应视野（AFOV）成像的波束形成点数。在TSD中，对混合信号进行动态聚焦，而在AFOV成像中，根据显示的视野（FOV）大小调整波束形成信号的采样频率（即波束形成频率）。在本文中，使用体模和体内数据对所开发的波束形成器（即TSD-AFOV-PRBF）的图像质量进行了定量评估。从体模研究中发现，仅具有1024个波束形成点的TSD-AFOV-PRBF可提供与QD-PRBF相当的图像质量。对于160mm的视野大小，我们获得的对比度分辨率（CR）中位数下降了7.6%。随着视野大小的减小（例如，在85mm时CR下降2.3%），图像质量稳步提高。体内研究也得到了类似的结果。因此，TSD-AFOV-PRBF可以以显著降低的计算成本提供与传统波束形成器相当的图像质量。
