Microwave-Induced Thermoacoustic Imaging of Small Animals Applying Scanning Orthogonal Polarization Excitation

Microwave-induced thermoacoustic tomography (MITAI) has found diversified applications in biomedical related disciplines. This work reports a novel MITAI modality to homogenize the microwave power deposition in the sample and improve the image quality for small animal imaging via scanning orthogonal polarization (SOP) excitation. Although circular polarization excitation has been reported to enhance MITAI, we perform some simulation works using realistic breast phantoms to prove that the homogeneity of microwave power distribution in the phantoms using orthogonal polarization excitation is comparable to that using circular polarization excitation. Compressive sensing is also applied to enhance the time efficiency of the system. Experiments applying a mouse and a frog sample are conducted. The results indicate that the SOP excitation mechanism can completely reveal the structure of the small animals due to improved power homogeneity. The proposed MITAI-SOP technique is superior to circularly polarized antenna (CPA) based modality since the former avoids the deficiency of CPA in bandwidth, power capacity and efficiency. This work presents a practical and easy-to-implement paradigm for high-quality imaging of small animals and big biological samples using MITAI.