In vivo validation of a propulsion method for untethered medical microrobots using a clinical magnetic resonance imaging system

Models for MRI-based magnetic propulsion of untethered medical microrobots were validated both in vitro and in vivo using magnetic beads. In accordance with the theoretical models, a clinical MRI system has the capability to propel magnetic spheres with maximum velocity in blood vessels approximately twice the diameter of the device being navigated. The preliminary models were in accordance with data obtained in experiments performed in the carotid artery of a living swine where a 1.5 mm sphere was propelled with a velocity of 13 cm/s. These models were used in this paper to extrapolate the magnetic field gradients that will be required for propulsion and steering of magnetic particles and applicable for microrobots in blood vessels of various sizes, from the aorta to the capillaries.