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基于磁声耦合效应的生物组织电特性功能成像方法在肿瘤的早期诊断方面具有重要研究意义,其中磁声信号时频特性是该检测成像方法信号检测处理和图像重建中的重要研究内容。本文基于磁声耦合格林函数解,采用基于时间延迟的波形求和方法,对矩形介质模型的准一维下声传播情况进行分析,计算磁声耦合声信号的时域波形,对不同厚度介质模型的磁声信号进行正问题仿真计算,并通过实验测量磁声信号波形验证仿真结果,证明了波形的叠加求和使不同电导率分布介质的磁声信号具有不同的时频特性。仿真结果表明,当介质厚度小于波形周期时,磁声信号宽度大于激励脉宽;随着介质厚度的增加,磁声信号脉冲宽度逐渐增加,峰值频率逐渐降低;当介质厚度大于激励周期时,磁声信号脉冲频率特性与激励频率近似相同。不同厚度介质样本的实验验证了仿真结果。该研究为磁声耦合成像中基于磁声信号时频特性对介质声源电导率的重建打下基础。
The functional imaging method based on the magneto-acoustic coupling effect of biological characteristics of biological tissue is of great significance in the early diagnosis of tumors. The time-frequency characteristics of the magneto-acoustic signal is an important research content in signal detection and image reconstruction of the imaging imaging method. Based on the magnetoacoustic coupling Green’s function solution, the time-delay-based waveform summation method is used to analyze the quasi-one-dimensional acoustic propagation of a rectangular medium model. The time-domain waveforms of the magnetoacoustic coupling acoustic signal are calculated, The simulation results show that the magneto-acoustic signals of different conductivity distribution media have different time-frequency characteristics. The simulation results show that the width of the magneto-acoustic signal is larger than the excitation pulse width when the thickness of the medium is less than the period of the waveform. As the thickness of the medium increases, the pulse width of the magneto-acoustic signal gradually increases and the peak frequency gradually decreases. When the thickness of the medium is greater than the excitation period, The acoustic signal pulse frequency characteristics are approximately the same as the excitation frequency. Experiments with different thickness media samples verify the simulation results. This study lays the foundation for the reconstruction of medium sound source conductivity based on the time-frequency characteristics of magneto-acoustic signals in magnetoacoustic coupling imaging.