Design of a robotic Transcranial Magnetic Stimulation system

Transcranial Magnetic Stimulation (TMS) is an excellent and non-invasive technique for studying the human brain. Accurate placement of the magnetic coil is required by this technique in order to induce a specific cortical activity. Currently, the coil is manually held in most of stimulation procedures, which does not achieve the precise clinical evaluation of the procedure. This paper proposes a robotic TMS system to resolve these problems as a robot has excellent locating and holding capabilities. The proposed system can track in real-time the subject's head position and simultaneously maintain a constant contact force between the coil and the subject's head so that it does not need to be restrained and thus ensure the accuracy of the stimulation result. This paper focuses on the coil positioning technique. An optical tracking system is used in the system for guiding and tracking the motion of the robot and inadvertent small movements of the subject's head. The calibration between the tracking system and robot coordinate systems is solved using a mathematical method which yields a matrix equation of the form AX = XB. Finally, a tracking control algorithm is inferred and obtained using the relationship of relative coordinate systems which can be used in the real-time tracking strategy.