Influence of System Matrix Concentration and Frequency Selection on Reconstructed MPI Signals

In Magnetic Particle Imaging (MPI), the system matrix (SM) characterizes the spatial encoding properties of the imaging system and the magnetic nanoparticle response. Ideally, for linear particle magnetization behavior, the concentration at which the SM is measured should not affect the reconstructed image. In this study, two SMs recorded with tracer concentrations of 8.5 mg(Fe)/ml and 1.92 mg(Fe)/ml were investigated. We show that, although the same SM is used, reconstruction discrepancies occur when the frequency coverage differs. We therefore propose to determine the usable frequency components based on the lower concentration SM to ensure a consistent reconstruction basis.