超声声辐射力弹性成像中基于拉东变换的剪切波速度估计方法的改进研究

能够无创定量测量人体组织弹性模量的声辐射力脉冲超声弹性成像方法，已经逐渐成为进行肝硬化分期和乳腺癌良恶性判别等临床诊断的重要工具。但是，在临床实践中也发现，弹性模量测量的稳定性会受到测量深度和组织各向异性等多种因素的影响。因此，如何通过算法的改进提高声辐射力脉冲超声弹性成像测量结果的可靠性，一直是该领域所关注的重要课题之一。文章对现有的基于拉东变换的剪切波速度估计算法进行了多种方式的改进，并利用自主研发的声辐射力定量超声弹性成像系统所采集的超声射频数据，对几种方法得出的剪切波速度测量结果进行了比较。这些改进算法可以被分为两类：(I)在以“时间-侧向位置”为坐标的位移矩阵上进行拉东变换；(II)在以“时间-深度”为坐标的位移矩阵上进拉东变换。第一类算法试图找到在某一个特定深度上剪切波侧向传播的最佳拟合轨迹，而第二类算法则试图直接找到在整个测量深度范围内，剪切波波前通过每个侧向位置的准确时间点。文章在标准弹性仿体和离体猪肉组织样本上进行了测量实验，比较了在不同深度位置上重复测量结果的可靠性，以及这些算法的耗时情况。实验结果将有助于我们找到一种兼顾测量稳定性和计算速度的新型剪切波速度估计算法，并将其应用到声辐射力脉冲超声弹性成像中，提高其测量结果的可靠性和在临床应用中的价值。

Study on Modified Shear Wave Speed Estimation Algorithms Based on Radon Transformation in Acoustic Radiation Force Impulse Imaging

Quantitatively assessing the tissue stiffness with the acoustic radiation force impulse imaging
(ARFI) method has proved its effectiveness in clinical trials, such as the staging of liver cirrhosis and diagnosis of benign and malignant breast tumor. However, it has also been found that, the stability of its result is affected by many factors, such as measurement depth and tissue’s anisotropy. In this study, several modiifed methods for shear wave speed estimation were designed based on the existing Radon transformation (RT) method, and were compared using ultrasound radio-frequency data collected from a self-developed ARFI system. These RT based algorithms were classiifed to two types: (I) RT being performed on the displacement matrix with the axes of time and lateral location, and (II) RT being performed on the displacement matrix with the axes of time and depth. Type (I) algorithm attempts to ifnd the best iftting trajectory of shear wave propagation in the lateral direction at a given depth, while Type (II) algorithm tries to directly ifnd the exact time points when the shear wave front passes each lateral location in the whole measurement depth range. Experiments were performed on the soft tissue mimicking phantom and the ex vivo pork tissue sample. The reliability of repeated measurements and the computation time of these modiifed algorithms were compared. These results can help to ifnd the most stable and time-saving algorithm of shear wave speed estimation, and improve the measurement reliability of ARFI in clinical trials.