UC Berkeley

Magnetic Particle Imaging (MPI) is a noninvasive imaging modality that exploits the saturation properties of superparamagnetic iron oxide particles (SPIOs). A major thrust of MPI research aims to sharpen the magnetic resolution of biocompatible SPIOs, which will be crucial for affordable and safe clinical translation. We recently reported on a new class of MPI tracers —called superferromagnetic iron oxide nanoparticles (SFMIOs) — which offer much sharper magnetic saturation curves. SFMIOs experimentally demonstrate 5-13x improvement in both resolution and sensitivity. However, superferromagnetism is a relatively unexplored branch of physics and the nanoscale physics and dynamics of SFMIOs remain a mystery. Here we show experimentally that chaining of SPIOs can explain SFMIO’s boost in SNR and resolution. We show how concentration, viscosity, transmit amplitude, and prepolarization time can all affect SPIO chain formation and SFMIO behavior. These experiments will inform strategies on SFMIO chemical synthesis as well as SFMIO data acquisition pulse sequences.