中文摘要：

磁热声成像（MMTAI）是一种新型的人体疾病早期检测电阻抗成像技术，融合了传统电阻抗成像高对比度和超声成像高分辨率的优势。为了验证磁热声成像针对生物组织的可行性，研究了磁热声成像的原理，并搭建了相应的实验系统。研究结果表明：将低电导率目标体置于μs级脉冲宽度的脉冲磁场中，会在目标体内产生涡流，目标体吸收焦耳热后瞬时膨胀并发出声信号，声信号含有目标体的电导率信息；利用电磁场与声场理论所推导的目标体声源计算式反映了声源与电导率之间的关系；对磁-热-声多场耦合作用下产生的热声信号进行检测和分析，再利用时间反演法重建声源分布；将含质量分数10％氯化钠的凝胶仿体模型置于μs级脉冲宽度的脉冲磁场中，采用中心频率为1MHz的超声换能器采集超声信号，信号被放大60dB后的峰峰值约为4mV，利用旋转凝胶仿体采集的100组信号所重建的热声图像能反映低电导率凝胶仿体的电导率分布。此实验验证了该方法用于低由导率介靥成像的可行件．为该方法用干生物组织成像的研有槔供了依椐。

英文摘要：

Magnetically mediated thermoacoustic imaging （MMTAI） is a novel electrical impedance tomography for early detection of human diseases, which combines the advantages of high contrast of the classic electrical impedance tomog- raphy with the high spatial resolution of sonography. In order to verify the feasibility of magnetically mediated thermoacoustic imaging for biological tissues, the principle of magnetically mediated thermoacoustic imaging was studied and the experimental system was established. The study results demonstrate that when a microsecond width pulse mag- netic field is applied to an object, the object absorbs Joule heating and causes heat expansion due to the effect of induced eddy current in the object. The ultrasonic signals are sent out, which involves the conductivity information of the object. Based on the theories of electromagnetic field and acoustic field, the calculation formula of acoustic source was deduced, which revealed the relationship between acoustic source and conductivity of the object. Thermoacoustic signals produced under the action of the magneto-thermos-acoustic multi fields were detected and analyzed to reconstruct the acoustic source distribution by time reversal algorithm. The gel phantom model with the mass fraction of 10% sodium chloride was placed in the microsecond width pulse magnetic field, which caused thermoaeoustic signals. After the signals were detected by ultrasonic transducer with the center frequency of 1 MHz and amplified by 60 dB, the peak value of the sig- nals was about 4 mV. The reconstructed thermoacoustic image using 100 sets of data, which were acquired by rotating the gel phantom, could reflect the conductivity distribution of the low conductivity gel phantom. The experiments verifiy that the method for low conductivity medium imaging possesses the feasibility, and provides a basis for its potential applica- tions to imaging in biological tissues.