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三维超快成像是超声技术发展的重要方向. 基于二维全采样阵列的传统三维成像方法需要较多成像阵元和采样通道, 其紧密的阵元排列设计也客观上限制了阵列孔径大小和成像分辨率. 行列寻址(row-column addressing, RCA)探头以行列检索的方式将通道数自 N
$ \times $ N减少为 N$ + $ N, 从而极大地降低了阵列的硬件实现成本. 本文仿真了中心频率为6$ {\rm{M}}{\rm{H}}{\rm{z}} $ 的128行+128列的RCA阵列, 结合多角度平面波正交复合成像方法, 通过延时叠加(delay and sum, DAS)波束合成、基于特征值分解(singular value decomposition, SVD)的杂波滤除和自相关多普勒速度求解算法, 实现了血流仿体的多普勒成像, 并分析了不同复合角度序列对成像效果的影响. 定量分析表明, 当角度数从5个增至33个时, –6 dB分辨率从0.986 mm提升至0.493 mm; 当复合角度为17个时, 功率多普勒图像的SNR可达30 dB, 彩色多普勒沿直径方向的速度分布和真实值的平均误差约为26.0 %. 以上结果表明, 基于RCA阵列的三维成像技术能够获得三维B-mode、功率多普勒和彩色多普勒图像, 增大复合平面波角度数和角度范围可显著提高成像质量. 本研究对于三维超快超声多普勒成像技术发展具有借鉴意义, 相关方法有应用于血流血管成像, 并进一步实现基于神经-血管耦合的组织功能监测与成像的潜力和前景.Three-dimensional (3D) ultrafast imaging is important for ultrasound technology development. The traditional 3D imaging method based on fully sampled two-dimensional (2D) matrix often requires a large number of electronic channels with high density which limits the aperture size and imaging resolution in application. Recently developed row-column addressing (RCA) matrix effectively reduces the number of electronic channels from N× Nto N+ Nby addressing the row and column elements. The beamforming strategy designed for 3D ultrasound imaging was based on the coherent compounding of orthogonal plane waves (OPW). Such a multi-angle OPW compounding strategy achieves virtual transmit focusing in both directions by transmitting a set of plane waves in one direction and receiving along the orthogonal direction, which finally leads to an isotropic point spread function (PSF). In this paper, multi-angle OPW method was investigated for 3D blood flow imaging using an RCA matrix with 128 rows and 128 columns, centered at 6 MHz. The delay and sum (DAS) beamforming was developed for coherent OPW compounding, and the singular value decomposition (SVD) filtering method was used for separating the dynamic blood flow signals from the static tissue signals and low-amplitude noise. The Doppler velocity was computed by the autocorrelation method, and finally the 3D power Doppler and color Doppler imaging of the blood flow were realized. To evaluate the imaging quality and investigate the effect of different OPW tilting angles, quantitative analysis was carried out using multiple parameters, including –6 dB resolution measurements of the PSF, SNR of the power Doppler images and velocity distribution of the color Doppler. The –6 dB resolution is improved from 0.986 mm to 0.493 mm with the number of angles increasing from 5 to 33. With 17 plane wave angles, the SNR of the power Doppler image reaches 30 dB, and the average deviation between the velocity distribution along the diameter of the blood flow phantom and the actual value is about 26.0%. In conclusion, results show that the ultrafast 3D imaging method based on RCA matrix can obtain 3D B-mode, power Doppler and color Doppler images. Increasing the number of tilting angles and enlarging the angle range can significantly improve the imaging quality. The proposed method can be helpful for developing 3D ultrafast ultrasound Doppler imaging and functional ultrasound imaging based on neuro-vascular coupling.-
Keywords:
- Ultrafast ultrasound/
- three-dimensional (3D) imaging/
- orthogonal plane wave (OPW)/
- row-column addressing (RCA) matrix/
- ultrasound Doppler
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阵元数 128+128 中心频率f0/MHz 6 声速c/(m·s–1) 1540 波长λ/μm 256.7 阵元中心间距/mm 0.2 阵元宽度/mm 0.175 阵列孔径/mm2 25.6$ \times $25.6 
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