Magnetic particle imaging using a multi-axis optically pumped magnetometer and multiple flux transformers

Biofunctionalized magnetic nanoparticles (MNPs) have been widely studied for biomedical applications, including magnetic particle imaging (MPI), which is a promising diagnostic technique for cancer imaging. Because MNPs generate weak magnetic fields, highly sensitive magnetic sensors, such as optically pumped magnetometers (OPMs), are required. In our previous study, we developed an MPI scanner using an OPM and a flux transformer consisting of input and pickup coils. For rapid and accurate MNP position estimation, it is desirable to measure the magnetic field using an OPM array. OPMs that measure magnetic fields along more than two axes are commercially available. However, OPMs are expensive and difficult to array. Therefore, we propose a method for multipoint measurements using a single OPM and multiple flux transformers. In an experiment, the MNPs were magnetized using an AC magnetic field, and the resulting magnetic signals were detected using two parallel differential-type pickup coils. The detected signals were converted into magnetic fields using orthogonal input coils and measured using a dual-axis OPM. Magnetic images were obtained by scanning a diluted Resovist MNP sample with a motorized stage. The signals from each pickup coil were measured independently and simultaneously, confirming the feasibility of multipoint measurements using a single multi-axis OPM. • A magnetic particle imaging (MPI) system using an optically pumped magnetometer (OPM) and multiple flux transformers was developed. • A novel method enables multipoint magnetic measurements using a single multi-axis OPM. • Multiple flux transformers with differential pickup coils detect weak magnetic nanoparticle signals. • Simultaneous multipoint detection using a multi-axis OPM for multi-axis and multiple flux transformers was experimentally demonstrated.