Magnetic particle imaging is a tracer-based tomographic imaging technique that uses static and oscillating magnetic fields to generate an image contrast from the spatial distribution of magnetic nanoparticles. Recent investigations have shown that multi-contrast MPI is able to generate additional contrasts from different tracer materials or their environments. In this project we investigate tracer properties and properties of the particle environment that influence the tracer relaxation behavior using multi-contrast MPI, such as

• temperature
• viscosity (e.g. viscosity quantification)
• mobility state (e.g. spatial orientation estimation of immobilized MNPs)
• material
• core/hydrodynamic size (e.g. nanoparticle core size discrimination)

To speed up the multi-contrast MPI image reconstruction, we have introduced an accelerated Kaczmarz algorithm. we have also introduced some potential medical and physical applications of multi-contrast MPI, such as 3D tracking of endovascular devices and balloon catheter imaging.