Electric vector-adapted thermoacoustic computed tomography for dynamic imaging sub-organ features in deep tissue

Abstract

Imaging biological tissue with high spatiotemporal resolution is essential for acquiring physiological and pathological information about organisms. Microwave-induced thermoacoustic (TA) tomography (MTAT) provides an effective combination of high spatiotemporal resolution, useful contrast, and deep tissue imaging capabilities. However, MTAT currently encounters challenges in visualizing sub-organ features within biological tissues. To address this issue, we propose electric vector-adapted thermoacoustic computed tomography (EV-TACT). EV-TACT takes into account the propagation of incident waves through biological tissues, employing microwave illumination with various polarizations to enhance energy coupling to specific sub-organ features. This method enhances the effective excitation of TA signals within the target tissue, improves the signal-to-noise ratio, and reveals structures that were previously not visible with conventional MTAT. The performance of EV-TACT has been evaluated through imaging the abdomen and brain in live mice, enabling the capture of the structure of nerve fiber bundles in the brain and the movement characteristics of the abdominal aorta. EV-TACT relies on tissue orientation information, and we also provide methods for resolving tissue orientation on arbitrary imaging cross sections to increase the universality of EV-TACT. These findings suggest that EV-TACT is a promising method for high-contrast, dynamic, and label-free imaging of target structures in deep tissues.