Estimation of magnetic nanoparticle diameter with a magnetic particle spectrometer

Magnetic particle imaging is a new tomographic imaging technique, which allows for measuring the spatial distribution of magnetic nanoparticles. It achieves high sensitivity and high spatial resolution, while keeping acquisition time short. As can be observed in simulations, the diameter of the nanoparticles has a high impact on the imaging quality in magnetic particle imaging. Thereby, only the iron core of the particle contributes to the measured signal. Thus, the diameter of the iron core is important for magnetic particle imaging, not the total size of particles. The coating of the iron core is essential for biocompatibility of particles with the human body. Most common techniques measure the total size of the particles. In this work, a method is presented to measure the iron-core size exploiting the non-linear magnetization curve of the particles. For this purpose, a magnetic particle spectrometer is used to measure the non-linear magnetization of the particles. Based on these measurements and the Langevin theory of paramagnetism, the particle-core size can be calculated. This, in turn, allows for more realistic simulations of the imaging performance in magnetic particle imaging.