Multiphysics simulation of microwave-induced thermoacoustic imaging based on complete acoustic process and its application in bone artifact analysis

Abstract

To address the issue of incomplete acoustic processes in microwave-induced thermoacoustic imaging (MITAI) simulations, this study proposes coupling structural mechanics (SM) and pressure acoustics (PA) fields inside and outside tissues, respectively, to visualize the entire MITAI physical process. Based on this, we investigate the MITAI artifacts formation mechanism from a mechanical property perspective. This study establishes a dual-imaging target model based on COMSOL, coupling electromagnetic, heat transfer, and SM and PA modules to achieve a complete MITAI process. This method is verified by extracting the signals for image reconstruction. Furthermore, four complex biological tissue models are constructed based on the presence and location of bone, to explore the mechanical impact of bone on surrounding soft tissues. The dual-target results show that the proposed method accurately characterizes the multiphysical phenomena of microwave excitation, energy deposition, thermal expansion, and ultrasound propagation in the MITAI process. The images correctly represent both dielectric functional information and structural features of the model, while also revealing artifacts caused by the signal reflection. The image of the dual-target phantom further validates this finding. Four complex models' results show that although MITAI clearly distinguishes bones and different soft tissues, the bones degrade image quality, with greater degradation occurring in soft tissues closer to the bones. The proposed method can achieve complete MITAI process visualization, overcome incomplete acoustic simulation, and elucidate the MITAI artifacts generation mechanism from mechanical properties. This work holds considerable value for advancing MITAI mechanism research and guiding biological tissue imaging applications.