Tracers and Particle Physics

The performance of an MPI system is determined as much by the tracer as by the scanner. Magnetic particle spectroscopy (MPS) measures the particle response in a well-defined excitation field and is the central tool to characterize tracers, to validate particle models and to acquire system matrices efficiently.

Clinically approved tracers. Resotran, an MRI contrast agent based on ferucarbotran, was characterized for MPI in a comparison study with established preclinical tracers. Its availability as an approved drug is an important step towards clinical MPI.

Superferromagnetic disk particles. Together with Empa and ETH Zürich, lithographically defined CoFe/Al₂O₃ multilayer disks were fabricated. Their superferromagnetic switching produces a particle response with steep harmonics that is very different from the Langevin behaviour of iron oxide nanoparticles and is attractive for MPI.

Synthetic antiferromagnetic nanodisks approach the physical limits of the specific absorption rate for magnetic hyperthermia under biologically acceptable field amplitudes and frequencies.

Particle models. Earlier work introduced a dynamic single-domain model with combined crystalline and shape anisotropy and a multidimensional magnetic particle spectrometer to measure the trajectory-dependent particle response.