超声造影技术中的波束激励控制新方法研究

The technology of ultrasound contrast agents provides a valuable means for the precise diagnosis and treatment of some diseases. Designing a beam excitation and control scheme that is appropriate for the properties of the contrast agent microbubbles is an unsolved but crucial issue in the ultrasound contrast agent technique. The current available beam exciation and control schemes manifest obvious problems. In the stage of imaging, current methods can not guarantee the stability of microbubbles. While taking the frangibility of microbubbles into the imaging consideration, the imaging quality is degraded. In the stage of treatment, microbubbles can not be broken precisely and safely for the drug delivering. This project consists of four stages including theory analysis, new feature extraction, beam excitation and control scheme designing, and phantom experiment. A new beam excitation and control scheme suitable for the microbubble properties is finally achieved by going through the four stages one by one. The project theoretically sets up a model for single contrast agent microbubble and studies the dynamic and acoustic behaviour of microbubble in the acoustic field. Based on the research results of the single microbubble model, a complex acoustic field containing microbubble clusters and tissues is then modelled. In the complex nonlinear acoustic field, the nonlinear echoes from microbubbles and tissues are investigated to get the vital features for the separtaion of signals from them. A beam excitation and control scheme incorporating plane wave and the newly founded features is built up. By combining effective and adaptive beam forming algirithm in the plane wave imaging, a novel ultrasound contrast agent imaging method with fast imaging speed, high resolution and high contrast/tissue ratio is finally developed. The project also provides theory and experiment foundations for the precise destruction of microbubbles in the drug delivery based on contrast agents.

超声造影技术为某些疾病的精确诊断和治疗提供了有利工具，设计适合造影剂微泡特性的波束激励控制方案是超声造影技术中亟待解决的关键问题。现有的波束激励控制方案存在明显问题：成像阶段不能保证微泡稳定性，而在兼顾微泡稳定性情况下又降低了成像质量；治疗阶段不能精准破坏微泡实现药物安全释放。 本项目从理论分析、新特征参数提取、波束激励控制方案设计、仿体实验四个层次，逐层深入设计适合造影剂微泡特性的波束激励控制新方法。项目在理论上研究单个造影剂微泡模型，探讨微泡在声场中的动力学及声学行为；结合单个微泡模型的研究结果，建立包含微泡群及组织的复杂声场模型；在非线性声场中研究微泡/组织产生的非线性回波，获取区分微泡与组织的特征参数；在此基础上设计基于平面波的波束激励控制方法，结合有效的自适应波束形成机制实现高速、高分辨率、高造影剂组织比的超声造影成像；为基于造影剂的给药治疗中精准破坏微泡提供理论和实验依据。

超声造影技术为某些疾病的精确诊断和治疗提供了有利工具，设计适合造影剂微泡特性的波束激励控制方案是超声造影技术中亟待解决的关键问题。本项目在理论上研究单个造影剂微泡模型，探讨微泡在声场中的动力学及声学行为；结合单个微泡模型的研究结果，建立包含微泡群及组织的复杂声场模型；在非线性声场中研究微泡/组织产生的非线性回波，获取区分微泡与组织的特征参数；在此基础上设计基于平面波的波束激励控制方法，结合有效的自适应波束形成机制实现高速、高分辨率、高造影剂组织比的超声造影成像。.项目组首先针对现有微泡模型参数较多的现状，在不降低模型准确率的前提下，提出一个改进的微泡模型；并且从微泡包膜的粘滞特性受微泡半径影响这一角度出发，加入了微泡的相互作用力，提出了包含微泡相互作用的群微泡模型；设计显微镜及高速摄影机实验平台来验证模型的准确性，实验结果显示我们的模型能很好地预测声诺维微泡声学特性。.其次，项目组针对微泡母小波技术中尺度因子需要遍历选择的现状，结合仿体实验给出尺度因子的理论选择，并提出基于微泡母小波和特征空间最小方差算法的微泡成像算法；针对现有超声造影成像仅仅根据微泡和组织间频谱差异来提高图像组织比的现状，项目组提出一种基于特征空间的微泡区域检测成像方法，同时考虑微泡与组织间的频谱差异以及它们在空间域的差异；针对特征空间区域检测方法难以处理组织中强散射点的缺点，将深度学习的理念应用到超声射频信号的二分类中搭建U-net网络进行信号分类从而提取微泡对应的射频信号区间，接着再应用微泡母小波结合特征值进行微泡信号的准确提取。.最后，项目组在仿体实验及兔子在体实验(肾部及耳静脉)中验证了项目所提出的微泡模型及成像方案方法的有效性，并在微血管成像和肝细胞肝癌诊断等实际应用中检验了所提出的方法。.共发表本项目标注学术论文27篇，其中SCI国际期刊论文17篇，国际会议论文6篇，申请发明专利及软件著作权5项。