Superferromagnetic iron oxide: A new paradigm for color multiplex and FRET-like nanoscale 'ruler' for Magnetic Particle Imaging

Superferromagnetic iron oxide (SFMIOs) is a new paradigm for Magnetic Particle Imaging (MPI) as it approaches the ideal imaging agent characteristics of a steep, step-like magnetization curve. Other than the expected 10-fold SNR and spatial resolution improvements from the square-like hysteresis curve, we demonstrate other unique qualities of SFMIOs that enable robust "chemical-shift-like" color multiplexing to potentially enable a range of magnetic "dyes" that work for at-depth imaging. We also demonstrate the extremely high sensitivity of SFMIO signal to the proximity of SFMIOs to each other, and explain how this could potentially be used as a FRET-like nanoscale ruler.