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Title:: Preliminary Study on the Thermoacoustic Effect in theMagnetoacoustic Tomography with Injecting Current

Author(s):: LI Junlin; ZHOU Xiaoqing; YIN Tao; LIU Zhipeng; Institute of Biomedical Engineering, Chinese Academy of Medical Sciences & Peking Union Medical College, Tianjin 300192, China

Keywords:: Magnetoacoustic tomography; Lorentz force; Thermoacoustic effect; Joule; Acoustic source

摘要:: 探究磁声成像中热声效应的影响。通过加载和不加载静磁场条件下，改变激励源的相位和幅值以及换能器的接收方向来验证铜、铝、石墨和凝胶四种不同特性样本被激发的磁声信号和热声效应信号，并进行分析。磁声成像中热声信号与激励电压的相位无关，其传播方向在各个方向都有，其幅值与激励的能量成正比。相对于其他样本而言，凝胶仿体中的热声效应的影响最大。在生物组织中进行磁声成像时，热声效应的影响不可忽略。

Abstract:: To discuss the thermoacoustic(TA) effect in magnetoacoustic tomography(MAT). The magnetoacoustic signals and thermoacoustic signals on four phantoms, which was made of copper, aluminum, graphite and gel, respectively. The acoustic signals was recorded while changing the phase and amplitude of the excitation signals as well as varying the receiving direction of the transducer. Also, the acoustic signals were analyzed in the time domain and the frequency domain, respectively. The thermoacoustic signals in MAT was independent of the phase of the excitation pulse, and displayed the non-vectorial property. Besides, the amplitude of the thermoacoustic signals was a quadratic function of the energy of the excitation. Compared to other samples, the thermoacoustic effect was more prominent in the gel phantom, which was the tissue-like materials. In the MAT, the thermoacoustic effect of biological tissue can not be ignored.