Highly flexible gradiometer coil arrangement offering improved passive compensation for multi-frequency MPI

In Magnetic Particle Imaging (MPI), the acquired receive signal will contain both the superparamagnetic iron oxide nanoparticle (SPION) signal as well as the excitation signal, where the former is to be maximized while the latter is to be reduced. Gradiometer receive coils can offer such reduction. Effective suppression of excitation feedthrough requires various degrees of freedom (DOF) for adjusting geometrical positions, amplitudes, etc. In this work, a suitable MPI coil arrangement is presented. The adjustment process is based on the signals acquired by the receive chain and can be fully automated. The coil arrangement is realized as a scanner with a diameter of approximately 34 mm; one dimension is scanned electrically while full three dimensional scanning can be achieved via the mechanical DOFs by means of a robotic stage. Electrical characterization shows passive feedthrough suppression of more than 100 dB at fundamental frequency. First measurements of SPION samples are presented.