基于超高速超声与脉搏波成像的局部血管弹性估计方法研究

Arterial elasticity (stiffness) is an important and independent predictor for mortality of cardiovascular disease, and pulse wave velocity (PWV) is the most frequently used measurement index. However, most existing methods only obtain global and average, instead of regional, value of PWV. Pulse wave imaging (PWI) is a novel vascular elasticity imaging technique and can obtain regional PWV of arteries and propagation patterns of pulse wave. Current PWI methods use retrospective electrocardiogram (ECG) gating to increase the frame rate, resulting in long data acquisition time and unstable results. In order to overcome these limitations, this project proposes to combine the new technique of plane wave based ultrafast ultrasound imaging and PWI, so as to significantly increase the frame rate of ultrasound radio-frequency data acquisition (from 50 frame/second to 1000-15000 frames/second) ,reduce the data acquisition time and improve the stability of PWI results. The image quality is improved by using ultrasound beam-forming and multi-angle compounding (i.e., coherent plane-wave compounding). The imaging method and algorithm parameters will be optimized through computer simulations and in-vivo data from healthy volunteers. The reliability of PWI results will be validated using phantom experiments. In addition, the clinical significance of the new PWI method will be tested through in-vivo experiments on patients with cardiovascular diseases such as hypertension and carotid atherosclerotic plaques. Non-invasive, quantitative and fast measurement of regional arterial elasticity (stiffness) will be achieved through this project and can hopefully be used in the evaluation of vascular damage caused by cardiovascular diseases and the prediction of risks.

血管弹性（或硬度）是心血管病死亡率的重要独立预测因子，而脉搏波速度（PWV）是最常见的测量指标，但目前的大部分方法只能获得全局、平均的PWV。脉搏波成像（PWI）是一种新型的血管弹性成像技术，可获得血管的局部PWV及其传播模式。为了克服现有PWI方法采用心电门控提高帧频、采集时间过长、结果不稳定的不足，本项目提出将最新的超高速超声成像技术与PWI相结合，通过并行数据采集，显著提高超声射频数据采集的帧频（50帧/秒提高至上万帧/秒），减小采集时间（15秒降至1-2秒），提高结果稳定性；通过波束合成与多角度复合，提高成像质量；通过计算机仿真和健康志愿者数据，优化成像方法与算法的参数；通过仿体实验验证结果的可靠性；进一步，通过对高血压、颈动脉粥样硬化斑块等心血管病患者的初步实验，测试新方法的临床意义。本项目将实现局部血管弹性的无创、定量与快速测量，可望用于对心血管病血管损害评价与风险预测。

脉搏波成像（PWI）通过高帧频超声成像对血管壁的运动进行成像，测量血管的局部脉搏波速度（PWV），用以评价血管的局部硬度。本研究建立了PWI方法，包括成像序列、位移估计与PWV测量，并通过计算机仿真、仿体实验与在体实验进行了验证。实现了基于降低扫描线、运动匹配和平面波发射的成像序列，提高成像帧频。提出了基于仿射模型的光流算法，提高了脉搏波位移估计的质量。建立了计算机仿真模型，系统地研究了关键参数对PWV测量效果的影响。在健康受试者、高血压受试者、颈动脉粥样硬化斑块受试者中，对比了基于不同脉搏波形的PWV测量方法。结果提供了PWI参数以及脉搏波形对估计影响的全面认识，为技术的优化以及标准化奠定基础，并证明了PWI的临床应用价值。针对近端大动脉的硬度评价，基于PWI，开发了升主动脉PWV测量方法，并在健康受试者中初步验证了方法的可行性。PWI实现了局部血管硬度的无创评估，可望用于心血管疾病的早期诊断和大量人群的筛查。项目取得丰富的研究成果。合计发表SCI论文26篇，包括医学影像领域的顶级期刊《IEEE Trans Medical Imaging》1篇，医学超声领域的主流期刊《IEEE Trans Ultrasonics, Ferroelectrics, and Frequency Control》7篇、《Ultrasound in Medicine & Biology》4篇、《Ultrasonics》3篇、高血压领域的主流期刊《Journal of Hypertension》1篇。多篇论文成为期刊的亮点/编辑精选/邀请/高引/高访论文。发表国际会议论文18篇，研究生6人次获得电气电子工程师学会（IEEE）国际超声年会（IUS）的Student Travel Support Award。获中国发明专利授权2项，获得国际PCT优先权1项，申请美国专利1项，申请欧盟专利1项，申请中国发明专利6项。