MPI Signal Performance of Resotran

Abstract

An important ingredient for clinical translation of Magnetic Particle Imaging (MPI) is the availability of superparamagnetic iron-oxid nanoparticles (SPIOs) with given medical approval for human interventions. Many SPIOs used as tracer-material in magnetic resonance imaging (MRI), do not have the magnetic properties needed for a potent signal generation in MPI. In particular they are often too small and thus the thermal energy dominates the magnetic energy leading to a linear magnetization behavior, which is not suitable for signal generation and spatial encoding in MPI. Some particle types are too large and block the Neél relaxation process due to strong magnetic anisotropies, reducing their ability to follow the field at excitation frequencies between 10 kHz to 150 kHz. At the same time, the medical approval of dedicated MPI tracers with optimal signal performance is very costly and tedious and will only turn profitable for companies with a clear clinical business case. Fortunately, there are some tracers that are suitable for both MRI and MPI and thus evaluating newly introduced MRI tracers is essential for potential human MPI studies. We show that the new MRI contrast agent Resotran (b.e.imaging GmbH, Baden-Baden, Germany, medically approved in 10/2022 under reg. no. 7002837.00.00 in Germany) is suitable for MPI. Initial Magnetic Particle Spectroscopy measurements indicate that Resotran shows a similar performance as the formerly approved tracer Resovist (Bayer Schering Pharma, Berlin, Germany) and the pre-clinical MPI tracer perimag (micromod Partikeltechnologie, Rostock, Germany). In combination with human-sized MPI systems, this paves the way towards first human MPI experiments.