高帧率超声成像建模及提高成像质量机理的研究

高帧率（high frame rate, HFR）医学超声成像是科研和临床对运动组织的成像需求。但由于发射次数少，HFR成像存在分辨率低，对比度差的问题。本申请项目旨在探索HFR成像机制，提高成像质量。a. 利用波动光学中角谱传播的概念，给出更一般化的HFR成像模型，该模型考虑到了发射加权函数，因此和实际超声发射系统更加吻合，并把目前基于有限衍射波HFR成像模型归纳为本模型的实例；b. 利用更一般化的成像模型，研究成像系统的PSF函数，找出成像旁瓣的分布特点，提出了一种抑制成像旁瓣的方法；c. 研究系统中发射加权函数，分析加权函数对成像模型作用，采用窗函数卷积处理以强化加权函数的冲激函数特性；d. 研究成像频谱和回波频谱之间的关系，利用频谱移动将回波信号的有效频谱分量迁移到成像频谱有效区域，降低了FFT的点数，提高了成像质量。本项目的实施，将为HFR成像系统的研发提供新的思路。

High frame rate (HFR) imaging can suit for the requirements of imaging on moving tissues in scientific researches and clinics, however, there exists problems of low resolution and poor contrast with HFR imaging due to a low number of transmit. The motivation of this project is to explore mechanisms of HFR imaging to improve the performance of HFR imaging.. a. The project presents a more generalized model of HFR imaging based on the concepts of propagation of angular spectrum in wave optics. This model takes into consideration the transmit weighting function, and thus fit for the actual ultrasonic transmit system. Moreover， the model of finite diffraction beam based HFR imaging is summarized as an example of the proposed model.. b. The project studies the point spread function (PSF) based on the more generalized imaging model, and find out the distribution characteristics of imaging sidelobe. Furthermore, this project proposes a method for suppression of sidelobe.. c. The project studies the transmit weighting function in system and analyses the contribution of weighting function for imaging model, and proposes to enhance the characteristics of impulse response of weighting function based on the convolution operation of window function.. d. The project studies on the relationship between the imaging spectrum and echo signal spectrum. The effective components in the echo signal spectrum are migrated to the effective region in the imaging spectrum based on the spectrum migration. So the point number of FFT is reduced and the imaging quality is improved. . The project will generate new idea in developing HFR ultrasound imaging system.