Drive-Field Frequency Dependent MPI Performance of Single-Core Magnetite Nanoparticle Tracers

The drive-field frequency of magnetic particle imaging (MPI) systems plays an important role for system design, safety requirements, and tracer selection. Because the commonly utilized MPI drive-field frequency of 25 kHz might be increased in future system generations to avoid peripheral nerve stimulation, a performance evaluation of tracers at higher frequencies is desirable. We have studied single-core magnetite nanoparticles that were optimized for MPI applications, utilizing magnetic particle spectrometers (MPS) with drive-field frequencies in the range from 1 to 100 kHz. The particles have core diameters of 25 nm and a hydrodynamic size of 77 nm. Measurements in the frequency range above 5 kHz were carried out with a newly designed MPS system. In addition, to exclude possible particle interaction, samples of different concentrations were characterized and compared.