Submillimeter magnetic particle imaging with low symmetrical field gradient

Abstract

Magnetic particle imaging (MPI) requires high field gradient to acquire sharp point spread function used to refine spatial resolution for submillimeter imaging of cells and small animal models. Since the steep field gradient potentially causes difficulty in the sample handling and the signal processing, minimizing the field gradient is more practical even though it degrades the spatial resolution. By modulating relaxation responses of magnetic nanotracers at two distinctive frequencies: 2 kHz and 1MHz, we reconstructed images of Resovist® sample placed in a 1.4×1.4 mm2 field of view. This modulated MPI implements 2 sets of permanent magnets of which the same polarity faces one another to create a 2 Tm-1 symmetrical field gradient on the xy plane and 3 Tm-1 on the z axis. Although the spatial resolution appears poor to differentiate two-neighboring circular phantoms of dense liquid samples, we could visualize a 1-mm ring-shaped solid sample with 0.1 mm thickness. Int. J. Mag. Part. Imag. 6(2), Suppl. 1, 2020, Article ID: 2009013, DOI: 10.18416/IJMPI.2020.2009013