A gradiometric receive coil is practically the modern standard in MPI. Although such a structure is one of the reliable and most effective ways of isolating the receive circuits from the influence of drive fields, it is challenging to implement it for the spatial sensitivity directions orthogonal to the cylinder axis of an MPI scanner. In this work, we demonstrate a concept of matrix coils based on spherical harmonic spatial sensitivity profiles. Our approach permits us to expand the number of independent receive channels in our head-sized MPI system to seven (and potentially more), while preserving important gradiometric characteristics of each channel.
Topcu et al. (Sun,) studied this question.