Kumar Viksit, Lee Po-Yang, Kim Bae-Hyung, Fatemi Mostafa, Alizad Azra
Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine and Science, Rochester, MN, USA.
Department of Biomedical Engineering, National Cheng Kung University, Tainan, Taiwan.
IEEE Access. 2020;8:76276-76286. doi: 10.1109/access.2020.2989337. Epub 2020 Apr 21.
Sparse arrays reduce the number of active channels that effectively increases the inter-element spacing. Large inter-element spacing results in grating lobe artifacts degrading the ultrasound image quality and reducing the contrast-to-noise ratio. A deep learning-based custom algorithm is proposed to estimate inactive channel data in periodic sparse arrays. The algorithm uses data from multiple active channels to estimate inactive channels. The estimated inactive channel data effectively reduces the inter-element spacing for beamforming, thus suppressing the grating lobes. Estimated inactive element channel data was combined with active element channel data resulting in a pseudo fully sampled array. The channel data was beamformed using a simple delay-and-sum method and compared with the sparse array and fully sampled array. The performance of the algorithm was validated using a wire target in a water tank, multi-purpose tissue-mimicking phantom, and carotid data. Grating lobes suppression up to 15.25 dB was observed with an increase in contrast-to-noise (CNR) for the pseudo fully sampled array. Hypoechoic regions showed more improvement in CNR than hyperechoic regions. Root-mean-square error for unwrapped phase between fully sampled array and the pseudo fully sampled array was low, making the estimated data suitable for Doppler and elastography applications. Speckle pattern was also preserved; thus, the estimated data can also be used for quantitative ultrasound applications. The algorithm can improve the quality of sparse array images and has applications in small scale ultrasound devices and 2D arrays.
稀疏阵列减少了有效增加阵元间距的有源通道数量。大阵元间距会导致旁瓣伪像,降低超声图像质量并减小对比度噪声比。提出了一种基于深度学习的定制算法来估计周期性稀疏阵列中的非有源通道数据。该算法利用多个有源通道的数据来估计非有源通道。估计出的非有源通道数据有效地减小了用于波束形成的阵元间距,从而抑制了旁瓣。将估计出的非有源阵元通道数据与有源阵元通道数据相结合,得到一个伪全采样阵列。使用简单的延迟求和方法对通道数据进行波束形成,并与稀疏阵列和全采样阵列进行比较。使用水箱中的线靶、多用途组织模拟体模和颈动脉数据验证了该算法的性能。对于伪全采样阵列,观察到旁瓣抑制高达15.25 dB,同时对比度噪声比(CNR)增加。低回声区域的CNR改善比高回声区域更多。全采样阵列和伪全采样阵列之间展开相位的均方根误差较低,使得估计数据适用于多普勒和弹性成像应用。散斑图案也得以保留;因此,估计数据也可用于定量超声应用。该算法可以提高稀疏阵列图像的质量,并且在小型超声设备和二维阵列中有应用。