| The Magnetic Stereotaxis System is a unique neurosurgical device that is designed to enable surgical treatment of regions of the brain which are, otherwise, inaccessible with contemporary neurosurgical techniques. By magnetically propagating a small ({dollar}sim{dollar}5 mm in length, 3 mm in diameter) magnetic implant through the brain with a catheter attached to the implant under near real-time fluoroscopic guidance while referencing preoperative MRI scans, both precision surgery and drug therapy can be applied to specific sites in the brain while circumventing the blood-brain barrier. The nature of the implant's movement control problem is one of regulating the magnetic fields produced by the six superconducting coils that constitute the actuators of the MSS. The treatment of the problem of magnetic implant guidance is one of organically incorporating the limitations of the superconducting coils and Earnshaw's theorem, as applied to quasi-static magnetic fields, so that a solution to the inverse problem as it pertains to the MSS can be solved. The following work addresses the complete computer control of the magnetic implant by incorporating the time-dependent, constant-power ramping behavior of the superconducting coils as well as the tribological response of the medium. Discussed are the field-generating and field-summing techniques. It is established that the minimization of a cost function is more useful in generating solutions for the currents than those methods which require specification of the moment orientation and the force (which constitute five of the six available degrees of freedom). |
