A novel method for magnetic nanoparticles deep optical imaging using SPAD

This paper proposes a novel magneto-optical imaging method that utilizes the superparamagnetic and optical properties of magnetic nanoparticles (MNPs). By measuring the rotation angle of linearly polarized light passing through MNPs under an external alternating magnetic field via the Faraday effect, we address the issue of optical signal attenuation in deep biological tissue imaging. We introduce a single-photon avalanche diode (SPAD) to detect extremely weak optical signals. Experimental results show that the harmonic signals of the Faraday rotation angle are linearly related to MNPs concentration. Under conditions with thick phantoms simulating deep tissue in the optical path, SPAD can still effectively detect polarization characteristics, verifying the feasibility of using the magneto-optical effect for high-resolution in vivo detection and imaging of deep biological tissues. This provides an exciting possibility for achieving high-resolution in vivo detection and imaging of deep biological tissues in the future.