Focus field based trajectory elongation in MPI

In Magnetic Particle Imaging (MPI), the data acquisition can be performed by steering a field-free point (FFP) through the field of view (FOV). When using drive fields to achieve the FFP movement, a fast spatial encoding of the FOV is enabled. Due to safety limits, in terms of patient heating and nerve stimulation, the amplitude of the applied currents needs to be small, which results in a small FOV. In order to enlarge the FOV, focus fields featuring a high amplitude and a low frequency can be used. In this contribution, an approach based on a linear focus field shift, which enlarges the FOV in axial direction, is proposed. Such a shift results in an elongation of a planar two-dimensional trajectory that features a controlled sub-sampling of the FOV.I Results show that a focus field based trajectory elongation in axial direction is a suitable data acquisition for MPI. In addition to this, the use of self-intersection points as trajectory specific axial distance measure has been proposed.