Tarbiat Modares University, Department of Biomedical Engineering, Tehran, Iran.
Wayne State University, Department of Biomedical, Detroit, Michigan, United States.
J Biomed Opt. 2018 Feb;23(2):1-15. doi: 10.1117/1.JBO.23.2.026002.
In photoacoustic imaging, delay-and-sum (DAS) beamformer is a common beamforming algorithm having a simple implementation. However, it results in a poor resolution and high sidelobes. To address these challenges, a new algorithm namely delay-multiply-and-sum (DMAS) was introduced having lower sidelobes compared to DAS. To improve the resolution of DMAS, a beamformer is introduced using minimum variance (MV) adaptive beamforming combined with DMAS, so-called minimum variance-based DMAS (MVB-DMAS). It is shown that expanding the DMAS equation results in multiple terms representing a DAS algebra. It is proposed to use the MV adaptive beamformer instead of the existing DAS. MVB-DMAS is evaluated numerically and experimentally. In particular, at the depth of 45 mm MVB-DMAS results in about 31, 18, and 8 dB sidelobes reduction compared to DAS, MV, and DMAS, respectively. The quantitative results of the simulations show that MVB-DMAS leads to improvement in full-width-half-maximum about 96%, 94%, and 45% and signal-to-noise ratio about 89%, 15%, and 35% compared to DAS, DMAS, MV, respectively. In particular, at the depth of 33 mm of the experimental images, MVB-DMAS results in about 20 dB sidelobes reduction in comparison with other beamformers.
在光声成象中，延迟和求和（DAS）波束形成器是一种常见的波束形成算法，具有简单的实现。然而，它导致分辨率差和旁瓣高。为了解决这些挑战，引入了一种新的算法，即延迟乘法和求和（DMAS），与 DAS 相比，它的旁瓣较低。为了提高 DMAS 的分辨率，引入了一种使用最小方差（MV）自适应波束形成与 DMAS 相结合的波束形成器，称为基于最小方差的 DMAS（MVB-DMAS）。结果表明，扩展 DMAS 方程会产生多个表示 DAS 代数的项。提出使用 MV 自适应波束形成器代替现有的 DAS。MVB-DMAS 进行了数值和实验评估。特别是在 45mm 的深度，与 DAS、MV 和 DMAS 相比，MVB-DMAS 的旁瓣分别降低了约 31、18 和 8dB。模拟的定量结果表明，与 DAS、DMAS 和 MV 相比，MVB-DMAS 导致全宽半最大值提高约 96%、94%和 45%，信噪比提高约 89%、15%和 35%。特别是在实验图像的 33mm 深度，与其他波束形成器相比，MVB-DMAS 的旁瓣降低了约 20dB。
