Investigation of impact of tuning coil loading on particle signal harmonics in multi-frequency MPI

In Magnetic Particle Imaging (MPI), suppression of the excitation feedthrough into the receive chain helps towards acquiring the fundamental frequency response of the superparamagnetic iron oxide nanoparticle (SPIONs), which is beneficial for quantitative measurements. As one approach, particularly suited for multi-frequency MPI (mf-MPI), tuning coil loading (TCL) has been shown to effectively reduce the feedthrough at the fundamental frequency way below the levels achievable with e.g. gradiometer coil arrangements alone. In this work, the effect of TCL on higher frequency components is evaluated by capturing the harmonics of a real particle signal, acquired by measurements at different excitation frequencies. A comparison between gradiometer-only and combined gradiometer plus TCL operation is presented. It is shown that TCL does not negatively impact the harmonics, hence provides an effective feedthrough suppression while preserving the higher frequency performance.