微波热声成像作为一种新型的生物医学影像技术，结合了微波成像和超声成像的优点，具有深穿透、高分辨率等优点，在基础研究和临床应用中具有较大的开发潜力。然而，由于微波波长通常与生物组织尺寸可比拟，因此微波的矢量特性对成像结果的影响显著。与之相关的因素，如生物组织的形状、尺寸、介电性质，可能导致成像结果产生伪影，引起图像失真，对后续的疾病诊断或治疗产生不利影响。针对该问题，本文首先分析了微波热声成像中物理伪影的潜在形成机制。在微波作用下，成像目标内部的极化分子和自由离子将随电场振荡，形成不均匀的电场分布。这将引起不均匀的电磁能量沉积，导致热声源分布的失真，从而影响了微波热声成像的准确性。其次，本文研究了一种基于新辐照方式的物理伪影抑制策略，即采用动态的微波入射矢量和极化方向对成像目标进行辐照，称之为动态激励策略。本论文通过理论推导、实验验证和仿真模拟，以及采用结构相似性作为量化指标，阐明了动态激励策略在更全面地采集信息、实现近似于电磁能量均匀沉积的成像效果，最终提高成像的准确性的作用。其中，采用平行于成像平面的入射方向和极化方向进行辐照，具有最佳的成像效果。

Microwave-induced thermoacoustic imaging (MTAI) is a novel biomedical imaging technology that combines the advantages of microwave imaging and ultrasound imaging, with benefits such as deep penetration and high resolution. It has great potential for development in basic research and clinical applications. However, when the wavelength of microwaves is comparable to the size of biological tissues, the vectorial characteristics of microwaves are significantly enhanced. Factors related to biological tissues such as shape, size, dielectric properties, etc., can produce physical artifacts, leading to image distortion that eventually hamper the subsequent disease diagnosis or treatment. To address this issue, this thesis first examines part of the formation mechanisms. It suggests that the movement of polarized molecules and ions under the influence of an electric field, leads to an uneven distribution of the electric field. This will cause uneven deposition of electromagnetic energy, resulting in distortion of the distribution of thermoacoustic sources, thus harming imaging accuracy. Next, a physical artifacts suppression strategy based on a new irradiation method is proposed. It involves using dynamic transformation of the microwave incident vector and polarization for irradiation, called the dynamic excitation strategy. Through theoretical derivation, experimental verification, simulation, and using structural similarity as a quantitative indicator, the thesis elucidates the role of this strategy in more comprehensive information collection, achieving imaging effects approximating uniform deposition of electromagnetic energy, and ultimately improving imaging accuracy. Among them, irradiation with incidence and polarization directions parallel to the imaging plane achieves the best imaging effect.