Zhou Xinhuan, Vincent Peter, Zhou Xiaowei, Leow Chee Hau, Tang Meng-Xing
Department of Bioengineering, Imperial College London, United Kingdom.
Department of Aeronautics, Imperial College London, United Kingdom.
Ultrasound Med Biol. 2019 Nov;45(11):3042-3055. doi: 10.1016/j.ultrasmedbio.2019.06.402. Epub 2019 Aug 2.
3-D blood vector flow imaging is of great value in understanding and detecting cardiovascular diseases. Currently, 3-D ultrasound vector flow imaging requires 2-D matrix probes, which are expensive and suffer from suboptimal image quality. Our recent study proposed an interpolation algorithm to obtain a divergence-free reconstruction of the 3-D flow field from 2-D velocities obtained by high-frame-rate ultrasound particle imaging velocimetry (High Frame Rate echo-Particle Imaging Velocimetry, also known as HFR Ultrasound Imaging Velocimetry (UIV)), using a 1-D array transducer. The aim of this work was to significantly improve the accuracy and reduce the time-to-solution of our previous approach, thereby paving the way for clinical translation. More specifically, accuracy was improved by optimising the divergence-free basis to reduce Runge phenomena near domain boundaries, and time-to-solution was reduced by demonstrating that under certain conditions, the resulting system could be solved using widely available and highly optimised generalised minimum residual algorithms. To initially illustrate the utility of the approach, coarse 2-D subsamplings of an analytical unsteady Womersely flow solution and a steady helical flow solution obtained using computational fluid dynamics were used successfully to reconstruct full flow solutions, with 0.82% and 4.8% average relative errors in the velocity field, respectively. Subsequently, multiplane 2-D velocity fields were obtained through HFR UIV for a straight-tube phantom and a carotid bifurcation phantom, from which full 3-D flow fields were reconstructed. These were then compared with flow fields obtained via computational fluid dynamics in each of the two configurations, and average relative errors of 6.01% and 12.8% in the velocity field were obtained. These results reflect 15%-75% improvements in accuracy and 53- to 874-fold acceleration of reconstruction speeds for the four cases, compared with the previous divergence-free flow reconstruction method. In conclusion, the proposed method provides an effective and fast method to reconstruct 3-D flow in arteries using a 1-D array transducer.
三维血流矢量成像在理解和检测心血管疾病方面具有重要价值。目前，三维超声矢量血流成像需要二维矩阵探头，这类探头价格昂贵且图像质量欠佳。我们最近的研究提出了一种插值算法，该算法利用一维阵列换能器，从高帧率超声粒子图像测速技术（高帧率回波粒子图像测速技术，也称为HFR超声成像测速技术（UIV））获取的二维速度中，获得三维流场的无散度重建。这项工作的目的是显著提高我们之前方法的准确性并减少求解时间，从而为临床转化铺平道路。更具体地说，通过优化无散度基以减少域边界附近的龙格现象来提高准确性，通过证明在某些条件下，可以使用广泛可用且高度优化的广义最小残差算法来求解所得系统，从而减少求解时间。为了初步说明该方法的实用性，使用计算流体动力学获得的解析非定常沃默斯利流解和定常螺旋流解的粗二维子采样成功重建了全流解，速度场的平均相对误差分别为0.82%和4.8%。随后，通过HFR UIV获得了直管模型和颈动脉分叉模型的多平面二维速度场，并从中重建了全三维流场。然后将这些结果与在两种配置下通过计算流体动力学获得的流场进行比较，速度场的平均相对误差分别为6.01%和12.8%。与之前的无散度流重建方法相比，这些结果表明这四种情况的准确性提高了15%-75%，重建速度加快了53至874倍。总之，所提出的方法提供了一种使用一维阵列换能器重建动脉三维血流的有效且快速的方法。
