Dielectric Resonance-Based Microwave-Induced Thermoacoustic Imaging (DR-MTAI)

Microwave-induced thermoacoustic (TA) imaging (MTAI) enables visualization of intrinsic electromagnetic properties of bio-tissues with high resolution and deep penetration depth, offering strong potential for disease diagnosis and therapeutic evaluation. However, the insufficient difference in electrical conductivity between diseased and normal tissues limits the imaging sensitivity, thereby constraining its clinical applicability. To address this challenge, we propose dielectric resonance-based MTAI (DR-MTAI), which exploits the Fabry–Pérot resonance and spatially nonuniform mode field distributions within a dielectric resonance plate (DRP) to achieve energy concentration. Through theoretical analyses and simulations, we quantify the energy concentration capabilities and optimize the performance of the DRP. Phantom experiments demonstrate that DR-MTAI achieves approximately a 4.8-fold improvement in imaging contrast. The following in vitro experiments demonstrate a threefold enhancement in TA signal amplitude at a penetration depth of 4 cm. Furthermore, the combination of DR-MTAI with raster scanning significantly boosts the imaging sensitivity over a large region of interest (ROI)$\sim 70\times 70$mm. All the experiments suggest that the proposed method holds promise for future clinical applications.