Real-Time 3D MPI-Based Navigation Scheme for Microrobots With Flexible Field Free Point Trajectories and Virtual FFP Intuitive Manipulation

Magnetic Particle Imaging (MPI)-based navigation shows significant potential for accurately guiding microrobots to desired target locations. Existing MPI-based navigation systems have been limited to two-dimensional planar movements due to increased computational load and a lack of efficient 3D actuator schemes. So we introduce a real-time 3D MPI-based navigation scheme for microrobot, utilizing a flexible field-free point (FFP) trajectory scanning scheme and 3D virtual FFP (vFFP) intuitive manipulation. The FFP trajectory is chosen flexibly to enhance temporal resolution. A vFFP force model for actuator function, with high potential for interactive manipulation, is used to linearize the magnetic force concerning the relative positions of microrobot and the actual FFP. The proposed concept has been validated using the available 3D amplitude modulation MPI system with a 90 mm bore size and a 4 T/m/$ \bm{\mu_{0}} $ gradient. By employing a flexible FFP trajectory, the MPI system can achieve an image sampling rate of up to 4 Hz for a 3D Field of View (FoV) of 60 × 40 × 60 mm³, enabling real-time MPI-based navigation. Furthermore, the proposed navigation control strategy can reach any target outlet within the 3D blood model with a low mean error in vFFP linearization of less than 5%.