Navigation of Microrobots by MRI: Impact of Gravitational, Friction and Thrust Forces on Steering Success

Introduction Magnetic resonance navigation (MRN) uses MRI gradients to steer magnetic drug-eluting beads (MDEBs) across vascular bifurcations. We aim to experimentally verify our theoretical forces balance model (gravitational, thrust, friction, buoyant and gradient steering forces) to improve the MRN targeted success rate. Method A single-bifurcation phantom (3 mm inner diameter) made of poly-vinyl alcohol was connected to a cardiac pump at 0.8 mL/s, 60 beats/minutes with a glycerol solution to reproduce the viscosity of blood. MDEB aggregates (25 ± 6 particles, 200 μm ) were released into the main branch through a 5F catheter. The phantom was tilted horizontally from − 10° to +25° to evaluate the MRN performance. Results The gravitational force was equivalent to 71.85 mT/m in a 3T MRI. The gradient duration and amplitude had a power relationship (amplitude=78.717 (duration)^-0.525 ). It was possible, in 15° elevated vascular branches, to steer 87