Continuous Focus Field Variation for Extending the Imaging Range in 3D MPI

The imaging volume that is rapidly encoded by drive fields in 3D magnetic particle imaging is limited by power dissipation and nerve stimulation thresholds. Additional coils have been implemented to generate so-called focus fields that operate at lower frequencies and extend the accessible imaging range. This contribution presents the possibility of sweeping the rapidly encoded imaging volume along an arbitrary 3D path using continuous focus field variations. This technique can be useful for following a tracer bolus, for tracking devices, or for dynamically moving the image focus to different regions of interest.