基于血管内超声成像的弹性成像方法研究

发布时间：2018-09-13 07:05

【摘要】：血管内超声成像（Intravascular ultrasound，IVUS）是一种目前用于评估动脉粥样斑块形态、动脉粥样硬化药物治疗和非药物性干预进程以及动脉粥样硬化易损程度的重要手段，被称为冠状动脉检查的新的“金标准”。1991年，Ophir和其研究小组首次提出超声弹性成像技术（Elastography），利用超声换能器采集软组织受力形变前后的超声信号，计算其位移分布，继而得到组织的弹性图像，以此反映生物组织的弹性信息，现今被广泛应用于临床，如乳腺、前列腺等器官的检查。近年来，有研究表明将超声弹性成像技术运用到血管内超声成像技术中，不仅能够提供血管壁弹性等参量图像，而且能够通过分辨高低应变区域，，识别冠脉血管内不同斑块的相对生物力学特性，在斑块分类和检测斑块易损程度上具有重要的应用价值。但目前弹性成像技术尚未应用于商业化血管内超声成像系统。本课题组在国家科技支撑计划项目的资助下，开展超高频血管内超声成像探头与系统的研发工作。本论文的工作针对课题组自行研制的中心频率为50-60MHz的微型血管内超声换能器与成像系统，进行利用血管内超声弹性成像方法识别动脉粥样硬化斑块的研究，具体工作包括以下几个方面： (1)对课题组自主研发血管内超声成像系统的功能需求进行分析，并设定了弹性成像方法的指标参数，继而对传统一维弹性成像算法及经典二维超声弹性成像位移估计方法进行分类和研究，分析其优劣； (2)针对血管内超声成像系统的指标参数，对传统一维弹性成像算法应用于血管内超声成像系统识别动脉粥样硬化斑块进行了研究，通过有限元模型模拟仿真血管壁组织在正常血压波动范围内的形变过程，组合不同血压值下的血管壁组织位移，分析压力间隔对IVUS弹性成像的效果影响；同时在最佳压力差条件下，评估IVUS弹性成像方法对不同性质斑块识别的效果，为IVUS弹性成像功能在课题组自主研发的IVUS成像系统上的实际应用奠定了基础； (3)针对IVUS超声成像应用，设计正交实验方法，组合具有代表性的因素水平，并通过极差分析与方差分析，比较不同成分配比对仿组织体模在高频超声条件下（50MHz）的声学参数影响，为课题组自主研制的超高频IVUS探头测试提供数据指导及理论依据； (4)提出了一种改进的二维位移估计方法，结合数据点的多级搜索和单级跟踪的方法，体现了合理平衡计算量和计算精度的优点，更符合实时成像的血管内超声成像系统的要求。并设计了仿真实验来验证所设计的二维算法的成像效果及实时性，由仿真结果对一维及二维算法成像结果进行比较分析。
[Abstract]:Intravascular ultrasound imaging (Intravascular ultrasound,IVUS) is currently an important tool for assessing atherosclerotic plaque morphology, atherosclerotic drug therapy and non-drug intervention processes, as well as vulnerability to atherosclerosis. It is called a new "golden standard" for coronary artery examination. In 1991, Ophir and his research team first proposed the ultrasonic elastic imaging technique (Elastography), which uses ultrasonic transducer to collect ultrasonic signals before and after deformation of soft tissue, and to calculate its displacement distribution. Then the elastic image of tissue is obtained to reflect the elastic information of biological tissue. Now it is widely used in clinical examination such as mammary gland prostate and other organs. In recent years, studies have shown that the application of ultrasonic elastic imaging technology to intravascular ultrasound imaging can not only provide parametric images such as vascular wall elasticity, but also distinguish between high and low strain regions. Identifying the relative biomechanical properties of different plaques in coronary artery has important application value in plaque classification and plaque vulnerability detection. But at present, elastic imaging technology has not been applied to commercial intravascular ultrasound imaging system. The research and development of UHF intra-vascular ultrasound imaging probe and system is carried out by the project funded by the National Science and Technology support Program. In this paper, a micro intravascular ultrasonic transducer and imaging system with center frequency of 50-60MHz was developed by our research group, and the identification of atherosclerotic plaques by intravascular ultrasound elastic imaging was studied. The specific work includes the following aspects: (1) the functional requirements of intravascular ultrasound imaging system are analyzed, and the parameters of elastic imaging method are set up. Then the traditional one-dimensional elastic imaging algorithm and the classical two-dimensional ultrasonic elastic imaging displacement estimation methods are classified and studied. (2) the index parameters of intravascular ultrasound imaging system are analyzed. The traditional one-dimensional elastic imaging algorithm was applied to the identification of atherosclerotic plaque by intravascular ultrasound imaging system. The deformation process of vascular wall tissue in the range of normal blood pressure fluctuation was simulated by finite element model. The effect of pressure interval on IVUS elastic imaging was analyzed by combining the tissue displacement of vascular wall under different blood pressure values, and the effect of IVUS elastic imaging method on the recognition of different plaques was evaluated under the optimal pressure difference condition. It lays a foundation for the practical application of IVUS elastic imaging function in the IVUS imaging system, which is independently developed by the research group. (3) for the application of IVUS ultrasonic imaging, the orthogonal experimental method is designed to combine the representative factor level. By means of range analysis and variance analysis, the effects of different composition ratios on acoustic parameters of tissue mimic phantom under high frequency ultrasound (50MHz) were compared, which provided data guidance and theoretical basis for the test of UHF IVUS probe developed by our team. (4) an improved two-dimensional displacement estimation method is proposed, which combines the multi-level search of data points and the single-stage tracking method, and embodies the advantages of reasonable balance of calculation load and calculation accuracy. More in line with the real-time imaging of intravascular ultrasound imaging system requirements. Simulation experiments are designed to verify the imaging effect and real-time performance of the designed two-dimensional algorithm. The imaging results of one-dimensional and two-dimensional algorithms are compared and analyzed by the simulation results.
【学位授予单位】：中国科学院研究生院(长春光学精密机械与物理研究所)
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TB552;R543

【相似文献】