Magnetic particle imaging: Exploring particle mobility

Abstract

Magnetic Particle Imaging (MPI) is a promising new imaging modality, providing 3-dimensional imaging of magnetic nanoparticle tracers with high spatial and temporal resolution. Some recently developed experimental scanners have proven MPI to be feasible for small animal imaging. So far, one assumes that all particles contributing to the MPI signal share the same size distribution. An interesting extension of MPI would be to measure the mobility (or binding affinity) of the particles in the imaging volume. In this scenario, particles in certain regions may be partly immobilized by chemical binding, resulting in a transition from a Brownian to a Néel-dominated magnetization behavior – which is generally assumed for MNP tracers in blood. We propose that using two distinct frequencies, one below and one above the Brownian-Néel transition frequency, the binding state of the particles can be determined and utilized in MPI imaging. In this paper, we describe our MPI system and present simulations of 2-dimensional “Mobility MPI”.