合成孔径超声成像信号相位畸变自适应校正技术研究

发布时间：2018-01-05 01:23

本文关键词：合成孔径超声成像信号相位畸变自适应校正技术研究　出处：《西南交通大学》2017年硕士论文　论文类型：学位论文

【摘要】：合成孔径聚焦技术(SAFT)是超声无损检测研究学者们将合成孔径雷达应用于超声成像中的结果。超声波优点显著,穿透力很强,传播方向良好,不存在明确的衍射,且具有快速且高效的特点,因此受到青睐。但当超声波在非均匀介质中传播时,各处速度产生的差异将引入波前误差,材料内部的精细结构颗粒会产生反射杂波,使得接收信号中携带噪声,且传播过程中会发生声波衰减,材料表面起伏(即不平整)及衍射这一系列因素会造成超声图像携带相位畸变,因而图像分辨率低。为解决相位畸变问题进而提高图像分辨率,本文将研究超声信号中的相位畸变并校正。首先,本文介绍了四种超声合成聚焦成像方式及其各自优缺点,从中选择采用合成聚焦方法。同时,利用波达方向窗函数消弱超声波方向角对超声信号的影响,从而达到优化成像结果的目的。然后,详细论述超声合成聚焦信号中相位畸变的产生,分析其特性、建立数学模型并利用计算机模拟相位屏。常见的相位畸变校正方法是基于互相关系数的,根据传统的邻近互相关相位校正方法可衍生出自适应的互相关相位校正方法,本文研究一种利用解决优化问题的函数argmax的改进的自适应互相关相位校正方法。最后,利用计算机仿真不同的缺陷点和医学囊肿组织并加入相位屏,采用自适应及改进的自适应邻近互相关相位畸变校正方法处理含有相位差的仿真数据,利用合成孔径超声成像方式成像。对于单点和两点仿真结果,相位校正后的图像分辨率比校正前的有在2.5%～10.9%范围内不同程度提高;对于多点仿真结果,改进的自适应校正图像比自适应相位校正图像比校正前的图像峰值信噪比提高了 11.1%;对于囊肿组织仿真结果,相位校正后的图像对比度噪声比值比加相差的有在23.9%～52.7%范围内不同程度提高,由此证明自适应方法对于相位差校正的可行性和有效性。此外,利用Multi2000超声实验平台采集实际数据,获得携带相位畸变的信号,同样地,利用自适应及改进的自适应邻近互相关相位畸变校正方法对原始数据进行处理,取得合成孔径聚焦超声图像。对于单点和多点实验数据,相位校正后的图像分辨率比校正前的有在9.1%～17.1%范围内不同程度提高,再次验证了相位校正算法处理相差的可行性和有效性。
[Abstract]:Synthetic aperture focusing technique (SAFT) is ultrasonic nondestructive testing research of scholars of synthetic aperture radar used in ultrasonic imaging results. Ultrasound has many significant advantages, strong penetrating power, the propagation direction is good, there is no clear diffraction, and has the characteristics of fast and efficient, because this is favored. But when the ultrasonic wave propagation in an in a homogeneous medium, the difference throughout the speed generated will introduce the wavefront error, the fine structure of particles inside the material will have a reflection of clutter, which carry noise in the received signal, and the occurrence of acoustic attenuation in the transmission process, the material surface (i.e. not flat) and a series of factors will cause the diffraction of ultrasound image carrying phase the distortion of image resolution is low. In order to solve the problem of phase distortion and improve the image resolution, this paper will study the phase distortion in ultrasonic signal and correction. Firstly, this paper introduces four kinds of ultrasound Synthetic focusing imaging methods and their respective advantages and disadvantages, the synthetic focusing method from it. At the same time, the influence of the direction of arrival angle of window function weaken the ultrasonic ultrasonic signal, so as to achieve the purpose of optimizing the imaging result. Then, discussed in detail the ultrasonic synthesis phase distortion of focal signal in production, analyzes its characteristics, mathematical model and Simulation of phase screen by computer. The phase distortion correction method is common cross correlation coefficient based, according to the traditional adjacent cross-correlation phase correction method can be derived according to the cross-correlation phase correction method, correction method in this paper using an improved argmax function to solve the optimization problem of the adaptive cross-correlation phase. At last by computer simulation, the defect of different medical and cyst tissue and join the phase screen, using adaptive and improved adaptive neighborhood correlation phase A distortion correction method with the simulation data of the phase difference, using synthetic aperture ultrasound imaging mode imaging. For single point and two simulation results, the image resolution is improved after phase correction in 2.5% ~ 10.9% range in different degrees than before correction; for the simulation results, the improved adaptive image correction than adaptive phase correction image than before correction image peak signal-to-noise ratio is increased by 11.1%; the cyst tissue simulation results, phase corrected image contrast noise ratio and phase difference increased from 23.9% to 52.7% in the range of different degrees, which proves that the adaptive method for phase difference correction is feasible and effective. In addition, the use of Multi2000 ultrasonic experimental platform the actual data collection, obtain the signal carrying phase distortion similarly, adjacent cross-correlation phase distortion correction based on adaptive and improved The method used for processing the raw data, to obtain synthetic aperture ultrasonic image. For the single point and multiple point experimental data, image resolution phase correction after the increase in the 9.1% to 17.1% range different than before correction, again to verify the feasibility and effectiveness of the algorithm is the correction phase.

【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB559

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