基于超快速主动检测技术的感应式磁声耦合成像理论与实验研究

发布时间：2018-05-03 11:29

本文选题：磁声成像 + 有限元仿真　；参考：《深圳大学》2017年硕士论文

【摘要】：癌症已成威胁人类健康的首要杀手。肿瘤机理研究表明,在肿瘤的发展过程中,血管新生会导致组织电导率变化。因而,测量组织电导率对于疾病的早期无创诊断具有重要应用价值。磁声耦合成像是一种新型无创生物组织电特性功能成像技术,根据激励方式不同可分为注入电流式磁声耦合成像与感应式磁声耦合成像,目前感应式磁声耦合成像通常采用KV级高压?s级窄脉冲进行激励以达到mm级分辨率,其激励源设计实现难度较大,能量转换率不高,同时存在一定安全性问题,且其信号的检测采用单振元换能器多个角度旋转接收,采集时间长,接收到的微弱声信号易受到高频空间电磁场耦合干扰,限制了成像质量。针对目前感应式磁声耦合成像方法存在的问题,本文提出一种新的成像方法:采用低频连续正弦信号激励,简化了实验成像装置;另外,采用多普勒信号检测技术检测振动信号,对组织各质点微弱振动位移及振速信息进行主动探测,利用多通道超声数据采集系统提高采集效率,通过图像重建算法,实现组织电流密度(电导率)分布图实时成像。本文依据麦克斯韦方程组和纳维方程建立了电磁场-固体位移场耦合的数学模型;借助有限元工具COMSOL Multiphysics5.2a进行研究,构建激励线圈模型和模拟正常组织包裹病变组织的多层模型,对时变电磁场的空间分布进行分析,对不同线圈配置、电导率比、体积比、相对位置分布等模型内部感应电流和洛伦兹力的分布影响进行分析;搭建了振动信号采集实验平台,实现了实验系统的实时振动信号采集,进行了不同电导率分布模型仿体的实验研究,验证数学模型和仿真研究结果。仿真研究表明:平行双线圈产生的磁场特性明显优于单线圈磁场特性;感应电流与仿体电导率值、体积大小、分布位置相关。实验结果表明:位移及振速信息包含了电导率边界分布信息,进一步说明可由位移信号重建仿体内部电导率分布方法的可行性。
[Abstract]:Cancer has become the leading killer of human health. The study of tumor mechanism shows that angiogenesis leads to the change of electrical conductivity during tumor development. Therefore, the measurement of tissue conductivity has important application value for early non-invasive diagnosis of disease. Magnetoacoustic coupling imaging is a new type of functional imaging technology for non-invasive biological tissue electrical characteristics. According to different excitation modes, it can be divided into injection current magnetoacoustic coupling imaging and inductive magnetoacoustic coupling imaging. At present, inductive magnetoacoustic coupling imaging usually uses KV high voltage / s narrow pulse to obtain mm resolution. The design of excitation source is difficult, the energy conversion rate is not high, and there are some safety problems at the same time. The signal is detected by single vibrator transducer with multiple angles rotated and received, the acquisition time is long, the received weak acoustic signal is easily affected by high frequency spatial electromagnetic field coupling interference, which limits the imaging quality. Aiming at the problems existing in inductive magnetoacoustic coupling imaging method, a new imaging method is proposed in this paper: the experiment imaging device is simplified by using low frequency continuous sinusoidal signal excitation. Using Doppler signal detection technology to detect vibration signal, the information of weak vibration displacement and vibration velocity of each particle is detected actively. The multi-channel ultrasonic data acquisition system is used to improve the collection efficiency, and the image reconstruction algorithm is adopted. Real-time imaging of tissue current density (conductivity) distribution is realized. Based on Maxwell's equations and Navid's equations, the coupling mathematical model of electromagnetic field and solid displacement field is established, and the excitation coil model and the multilayer model to simulate the diseased tissue of normal tissue are constructed by using the finite element tool COMSOL Multiphysics5.2a. The spatial distribution of time-varying electromagnetic field is analyzed, and the distribution of inductive current and Lorentz force in different coil configuration, conductivity ratio, volume ratio and relative position distribution are analyzed. The real time vibration signal acquisition of the experimental system is realized, and the simulation results of different conductivity distribution models are verified. The simulation results show that the magnetic field produced by parallel double coils is obviously superior to that of single coil, and the inductive current is related to the conductivity, volume and distribution of the simulated body. The experimental results show that the information of displacement and vibration velocity contains the information of conductivity boundary distribution, which further demonstrates the feasibility of the method of reconstructing the conductivity distribution of the imitated body from the displacement signal.
【学位授予单位】：深圳大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TP391.41;R730.4

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