Gradiometric human head coil-coupled magnetoresistive sensor for sensitivity improvement in magnetic particle imaging

Abstract

Realization of magnetic particle imaging (MPI) for human brain scanner concerns safety limits while demanding high sensitivity to probe low magnetic signal from allowable tracer dosage. In order to reduce magnetostimulation effects, applying few kHz excitation field is optional with a high inductance receive coil having noisy output voltage around self-resonance frequencies. Here, we employed magnetoresistive (MR) sensor to improve signal quality of using gradiometric human head coil via flux transformer. This inductive current-sensitive detection of MR sensor provides low noise level to detect Langevin signal from a mini coil equivalent to magnetic moment of few microg Fe Resovist®. While our split gradiometer setup leads to considerable signal attenuation and feed-through suppression, we later preliminary confirmed the 3rd harmonic response of few mg Fe Resovist® sample. This value was still higher than the expected iron-mass sensitivity limit of the magnetometric system. Although ac current filtering (e.g., high-order resonant band-pass filter) is further necessary to compensate for harmonic noises and secure pure sinusoidal excitation, MR sensor-embedded receive chain appears applicable toward clinical MPI system.