Development of Rat-Scale Magnetic Particle Spectroscopy for Functional Magnetic Particle Imaging

Magnetic particle imaging (MPI) is a fast and sensitive technique for imaging of magnetic nanoparticle (MNP) concentrations. MPI directly measures and maps the particle concentration over a measured spatial position. Functional MPI (fMPI) is a specific application of MPI that aims to detect the change of cerebral blood volume (CBV) through imaging. Assuming that the concentration of MNPs in the CBV is uniform, the resultant concentration of MNPs can indicate the CBV changes. Magnetic particle spectroscopy (MPS) is basically a zero-dimensional MPI scanner which can be used to conduct spectroscopic studies and fMPI. In this letter, we suggest an MPS for fMPI with a bore size of 50 mm compatible with rat head dimensions. The system utilizes 0.015 T magnetic field at a frequency of 29.5 kHz and uses an integrated method to measure the small iron component of magnetic particles. Based on the integrated output signal, the MPS consisting of an excitation coil and a gradiometer coil with three parts—a receive coil, a cancellation coil, and a calibration coil—can detect down to 25 ng of Fe. The suggested MPS has demonstrated the achievement of sensitivity that is feasible for fMPI.