Background-free microwave-induced thermoacoustic imaging by magnetic field modulation

Microwave-induced thermoacoustic (TA) imaging is a potential noninvasive method for high resolution detection of deep tissues. However, background signals from non-target areas can limit imaging contrast. Here, we proposed a reversible switch microwave-induced TA differential imaging using the ferromagnetic resonance effect to achieve high-contrast and background-free imaging. The ferromagnetic resonance of ferromagnetic materials under the combined action of alternating magnetic field and biased static magnetic field can enhance microwave absorption and further produce stronger TA signal. The results demonstrated that the conversion of strong and weak TA signals of ferromagnetic materials can be realized by controlling the switch of biased static magnetic field, so as to achieve high-contrast and background-free TA differential imaging. This technology provides a potential approach for high-contrast and background-free microwave-induced TA imaging in complex biological tissues.