Perpendicular Magnetic Particle Imaging, pMPI

Abstract

Current magnetic particle imaging methods use an alternating magnetic field (AMF) to induce magnetization from the magnetic nanoparticles. The dominant component of the magnetization is in the same direction as the AMF; hence only the harmonics of the magnetization can be isolated from the AMF using their frequencies. We recently introduced a method of using a small static field to induce a component of the magnetization in the direction perpendicular to the AMF. The perpendicular magnetization is geometrically as well as spectrally decoupled from the AMF. The magnetization is generated as the AMF passes though zero and is entirely composed of even harmonics. The method was developed for spectroscopic sensing applications. Here we suggest that perpendicular magnetization can be used to image the spatial distribution of magnetic nanoparticles. Two gradient orientations can be used and simulations of the two were made to perform a preliminary comparison. In both cases, spatial gradients in static magnetic fields were employed. The direction of magnetic field is critical: In the first case, the static gradient fields are in the direction perpendicular to the AMF. In the second case, the static gradient fields are in the same direction as the AMF. In both cases, there would be gradients in all three directions. In both cases, the AMF can be large enough to image all pixels in the field of view at once, or a stepped static field can be used to break the field of view into subregions to reduce the power requirements on the AMF. Both methods should be able to produce low-noise images with reasonably conditioned reconstructions that are less than ten.