Two-voxel-analysis to assess the spatial resolution of a tracer in Lissajous-scanning magnetic particle imaging

Determining the imaging performance of a magnetic nanoparticle system employed as tracer in magnetic particle imaging (MPI) commonly requires the use of suitable phantom measurements. The imaging of real phantoms often shows variations due to uncertainties such as alterations of the MNP distribution, positioning uncertainties, distortions by evaporation, or air bubbles, that makes the assessment of the imaging performance between different tracer unreliable. To avoid these uncertainties, we developed the so-called 2-voxel-analysis using data extracted from the system function. We demonstrate the efficiency of the novel characterisation method applied to 13 different tracer systems. Augmented is the 2-voxel-analysis by measurements employing magnetic particle spectroscopy as a powerful tool to determine the dynamic magnetic behaviour of MNPs. Furthermore, based on the 2-voxel analysis, efficient virtual phantoms can be created, which enable a test environment for quantitative reconstructions since the exact quantitative tracer content of these virtual phantoms is known.