Contrast-enhanced continuous-terahertz-wave imaging based on superparamagnetic iron oxide nanoparticles for biomedical applications.

We present a novel contrast-enhanced continuous-terahertz-wave imaging modality based on magnetic induction heating of superparamagnetic iron oxide nanoparticles (SPIOs), which yields a highly sensitive increment in the reflection terahertz (THz) signal in SPIO solution upon exposure to an alternating magnetic field. In the differential and relative refection change focal-plane images before and after alternating magnetic field exposure, a dramatic contrast is demonstrated between water with and without SPIOs. This low-cost, simple, and stable contrast-enhanced continuous-THz-wave imaging system is suitable for miniaturization and real-time imaging application.