MRI systems as a mean of propulsion for a microdevice in blood vessels

The use of an MRI system as a mean of propulsion for a small robot for applications in blood vessels is being studied. The strong and variable magnetic field of the MRI system will exert three dimensional propulsion force to a ferromagnetic core that will be embedded onto the future small robot. The paper describes studies conducted concerning the ability of MRI gradients to propel a ferromagnetic body and the possibility to use MR images to track it. Experimental studies showed that a 3.175 mm diameter, 1010/1020 carbon steel sphere was able to withstand a maximum flow of 0.4115 l/min. in a 6.35 mm diameter tube when a magnetic field gradient of 18 mT/m was applied on it. Images made with spin echo and gradient echo sequences showed that imaging distortions (artifacts) caused by ferromagnetic cores are several times larger than the size of the core itself. It is critical to measure accurately the position of the future robot. The elimination or reduction of such ferromagnetic artifacts is currently a serious problem. Therefore, alternative solutions to the imaging problems like artifact cancellation, artifact pattern tracking softwares or magnetic tracking systems need to be developed.